Climate, Climatic Change, and Water Supply (1977)

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Methods for Estimating and Projecting Water Den~ancis for Water-Resources Planning I NTRO DU CTI O N EVERARD M. LOFTING University of California, Riverside H. CRAIG DAVIS University of British Columbia Longrun solutions to problems associated with scarce natural resources and raw materials are of critical impor- tance to the economies of industrialized nations. Water is undoubtedly one of the most critical of these scarce re- sources, although recently attention has been focused more upon various forms of energy. As both population and economic growth continue, there is an increasing need for the development of more effective planning models and strategies to meet the problems associated with expanding resource demands. In the market economies, except in times of extreme exigency, such as war, the allocation and distribution problems are solved by rising prices. The demand for certain resources is brought into balance with available supply at some new (higher) price level. In economic theory the concept of "demand" for a particular commodity is the schedule of quantities of the commodity consumers are willing to purchase at various prices. While the concept can be precisely defined for any good or service, the task of giving it operational and 49 empirical content with the same degree of exactness has traditionally been considerably more difficult. Economists have indicated on several occasions concern about the continuing use of the terms "requirement," "use," and "need" when referring to the withdrawal or intake of water as a natural resource." These terms are called into question because they do not have an alloca- tive connotation that is in keeping with the competitive market framework. Given the general problems associated with statistical demand estimation and, in the case of water, present conditions of"block pricing" and substitute goods such as self-supplied, reclaimed, or recirculated water, the pros- pect for determining demand functions relating to water (particularly for water as a production input) for purposes of policy formulation may remain tenuous for some time to come. In the sections that follow, the current state of the art of forecasting water demands or requirements is reviewed for the water-use categories of irrigation, minerals indus- tries, manufacturing industries, thermoelectric power, commercial, and municipal. Water-resource systems

50 planning and the role of water-use data in the develop- ment of water-use forecasts are discussed, and the possi- ble impact of climatic variability on water-use forecasting is considered. The paper concludes with a graphical comparison of existing water-use forecasts to the years 2000 and 2020 with the results of a simple forecasting model constructed by the authors. DEFINITION AND USE OF THE TERM ''DEMAND'' The concept of a demand schedule in its strictest sense applies only to consumer purchases. Purchases of re- sources and materials inputs by producers to satisfy the demands of consumers for specific products are more properly termed "derived" demands. The terms "water requirements" or "water use" have been historically as- sociated with water development planning and do not carry any precise or rigorous connotation of quantitative measurement of water withdrawals in relation to price. They are generally used in an engineering or technologi- cal context to relate the quantity of water employed in the production process per unit of output. The use of the term "water demand," as opposed to "water requirements" or "water use," carries with it the implication that the impact of price on the amount of water being withdrawn has explicitly been taken into consideration and that the amount being withdrawn is the smallest amount needed for whatever purpose to minimize costs to the withdrawer. This may be true if the withdrawer is an individual consumer. If, as a matter of policy, prices of public supplies are increased to agricultural and industrial pro- ducers, there is no guarantee that they will in fact use less water but in times of inflation may simply pass the in- creased costs on to the purchasers of their products and ultimately to consumers, adding further upward pressures to market prices. This has been a vexing matter. In the market economies, there has been a continuing search for more precise policy instruments that have greater cer- tainty of achieving a more efficient use of resources than certain autonomous increases in commodity prices. There is another aspect to the demand for water. Water is demanded for productive uses. There are also over- whelming demands for the waste-assimilation services of water. Pricing policies concerning the latter in the form of taxes and surcharges on pollutants and volume of outfalls have been long recommended. In the United States, events overtook these recommendations in 1972 in the fop- of amendments to the Federal Water Pollution Con- trol Act, known generally as Public Law 92-500. Under Phase I of the law, federal regulations require industry to install "best practicable control technology currently available" (BPT); Phase II requirements are intended to be more rigorous and more innovative. Industries are to install best available technology economically achievable (BAT) by July 1, 1983, and, ultimately, all point source EVERARD M. LOFTING and H. CRAIG DAVIS controls are directed toward achieving the national goal of the elimination of the discharge of pollutants (EOD) by 1985. In the case of irrigation, the Act requires the use of Irrigation Management Services (IMS), in which water use and return water discharges are to be scientifically managed to ensure minimal use and minimal discharge. Under the provisions of Public Law 92-500, revolutionary changes in water use in most sectors can be expected, and the projection of water "demands" should ultimately be subject to some minimal technological requirements in most cases. If the provisions of the Act are enforced in the agricultural and industrial sectors, water demands and water requirements may become essentially equivalent regardless of the withdrawal price of water. STATE OF THE ART OF FORECASTING DEMANDS Projections of demands for water are usually made for the major industry divisions and the household (residential) sector of the economy. Traditionally, however, water-use categories and economic-sector categories have not been aligned. Specifically these categories can be listed as shown in Table 3.1. In order to bring the economic-sector categories into agreement with the Gross National Product and its com- ponents for analysis and projection purposes, the addi- tions to the economic sectors shown in Table 3.2 are necessary. This grouping provides an exhaustive, highly aggregated classification scheme for all productive sec- tors of the national economy or its geographic regions. The Gross National Product (GNP) iS a scalar quantity that is typically projected by federal agencies in constant dollar terms to various target years.2~3 The projected scalar values can then be decomposed into the sectoral compo- nents that reflect the relative growth or decline of these within Me overall control total. The resulting estimates can be termed "consistent." That is, the interdependent nature of the sectors of the economy is usually explicitly (or implicitly) recognized. If the individual sectors were projected on the basis of historical Rends or over criteria and the values summed for the target years, results may be inconsistent with more reasonable estimates of the GNP based on the material requirements of the projected population and resource availability. Moreover, since water is regional in its occurrence, the national control TABLE 3.1 Economic-Sector and Water-Use Categories Economic Sector Water Supply-Demand Category . 1. Irrigation 2. Mineral Industry Water Use 3. Industrial 4. Thermoelectric Power 5. Commercial 6. Municipal (Part) 1. Agriculture 2. Mining 3. Manufacturing 4. Utilities 5. Trade and Services 6. Households

Methods for Estimating and Projecting Water Demands for Water-Resources Planning TABLE 3.2 Additional Economic-Sector and Water-Use Categories Economic Sector Water Supply-Demand Category 1. Agriculture 2. Forestry and Fisheries 3. Mining 4. Construction 5. Manufacturing 6. Utilities 7. Transportation and Communication 8. Trade and Services 9. Households 1. Irrigation 2. 3. Mineral-Industry Water Use 4. 5. Industrial 6. Thermoelectric Power 7. 8. Commercial 9. Municipal (Part) totals can be disaggregated spatially to yield a furler consistency for the various sectoral components. Before dealing with We specific sector demand analysis and projections some further points should be made regarding the alignment of water supply-demand cate- gories with the economic-sector categories. Consistent estimates in money terms can be made for the GNP and its sector components as indicated above. It is desirable that these be matched (aligned) as closely as possible with water-demand estimates in physical terms, i.e., gallons per day or acre-feet per year. This is not an easy problem since the engineers and hydrologists gener- ally charged with the responsibility for gathering or esti- mating the water data do not choose their classifications to fit precisely with the economic-sector specifications. Water uses may be measured or gauged by the amount supplied in a given time period. Further, water may be impounded and supplied for certain joint uses, and it may not be known except in the most aggregate way which end use actually withdrew the water. For example, water may be impounded and distributed by a public water supply system. The water may be supplied to households, indus- try, municipal buildings, and commercial enterprises. In fact, multiple-unit dwellings are frequently considered a commercial use of water and are so classified by many water-supply agencies. Thus, commercial and multiple- unit dwelling household uses may be inseparable in the supplying agency's records, and other estimating tech- niques must be found to separate these for analytical purposes. The same type of end-use identification occurs for commercial and industrial uses from time to time. The overall alignment scheme suggested above is not entirely precise but is probably the most satisfactory for establish- ing aggregate control totals, given the nature of the basic water-use data as presently compiled. DEMAND ESTIMATING AND FORECASTING TECHNIQUES FOR AGRICULTURAL ( IRRI GA TI O N ) WA TE R The state of the art in estimating demand functions for water used in agriculture appears to be progressing at 51 three levels: (1) the micro, or small area, approach; (2) the macro interregional programming approach; and (3) the dynamic multisector model approach. Examples of We first approach are cited by Howe4: For consumer goods~and many producer inputs, we have data on prices, quantities sold, and other relevant variables sufficient to permit estimation of the demand function. For irrigation water, markets generally don't exist, prices are usually nominal and highly subsidized and unrelated to costs or willingness to pay. Transfers among uses are infrequent and sluggish. Thus, often we simply don't have the data needed to estimate the demand functions for irrigation water. It is then necessary to estimate farmers' willingness to pay for water by modeling their production operations and, upon the assumption that the farmer consciously or unconsciously is attempting to maximize profits, deducing how his applications of water would vary as the price of water is varied. This is most frequently done through linear programming models in which the activities represent different crops and methods of cropping (including different amounts of water). The same results can be deduced by placing a water constraint on production, plotting the relationship between the shadow price of water and the quantity available. Examples of excellent studies following this approach to the estimation of irrigation demands are Moore and Hedges,5 Young and Bre- dehoeft,6 Cummings,78 Stults,9 and Gisser.~° The resultant de- mand functions are either for individual farm or farms of different types,5 for a farming area,6 7 or for an entire region.8-~0 . . . Other methods are possible for estimating irrigation water demand functions. Hartman and Anderson estimated the value of irriga- tion water from farm sales data. Andersont2 has estimated ilTiga- tion water values from data on seasonal water rental markets in northeastern Colorado. Gardner et al.~3 have estimated irrigation water values from time series data on water rental values before and after consolidation to Utah irrigation districts. The outstanding example of the second approach is the interregional programming model developed by Heady.~4 The Heady model is formulated as a linear program, the solution of which yields the least-cost distri- bution of agricultural production by crop type and geo- graphic region, under various assumptions about resource availabilities and their costs, farm support programs, and consumer and export demand for agricultural products. The model was developed to use the following data as inputs. The 223 water-resource subregions defined by the U.S. Water Resources Council are used to specify the basic geographical production areas. In each production area the quantities of land that are available for various types of production are identified. These include crop land, irrigated crop land, dry land for tame hay or crops, irrigated land for tame hay or crops or land available only for pasture or wild hay, and land diverted by certain government programs. Consumptive uses of water for municipal, industrial, and specific on-site purposes (such as wet lands) and for fruit, vegetable, and rice growing are forecast as requirements for each water-supply region. The limitations of water and land serve as the major constraints on agricultural production in each geo- graphical area in the model. Additional constraints re- flecting the need for crop rotation and the need for satisfy-

52 TABLE 3.3 Correlative Water-Use Factors EVERARD M. LOFTING a nd H. CRAIG DAVIS P. X n—2 r r2 percent By river basin Total water Value of production 16 0.58 0.34 2 Total water (except natural gas processing) Quantity of crude material 16 0.66 0.44 1 New water (except natural gas processing) Do 16 0.68 0.46 1 Percent total water recirculated Average temperature 16 0.64 0.41 1 Consumed water Do 16 0.59 0.35 1 Do Humidity 16 -0.54 0.29 2 Do Recirculation 16 0.75 0.56 1 By commodity Total water (except natural gas processing) Quantity of crude material 33 0.62 0.38 1 Percent new water consumed Percent total water used for 17 0.69 0.48 1 cooling and condensing By states Recirculated water Value of product 43 0.61 0.37 1 Consumed water Temperature (30-year average) 43 0.43 0.18 1 Do Temperature (l-year average for 1962) 43 0.43 0.18 1 New water (treated) Population 1960 48 0.46 0.21 1 TABLE 3.4 Noncorrelative Water-Use Factors Y X n—2 r By river basin New water Average precipitation 17 0.04 Do Mean stream discharge 16 -0.01 Recirculated water Value of production 17 --0.14 Do Average precipitation 17 —O.1Q Do Mean stream discharge 16 - 0.12 Do Days with O.Ol-in. precipitation or more 16 -0.23 Do Humidity 16 -0.21 Recirculated water (except natural gas Days with O.Ol-in. precipitation or more 16 -0.24 processing) Percent total water recirculated Do 16 -0.42 Do Humidity 16 -0.33 Recirculation per ton crushed limestone Days with O.Ol-in. precipitation or more 16 0.52 Recirculation per ton sand and gravel Do 13 0.35 Consumed water Precipitation 17 -0.22 By commodity Total water Value of production 33 0.14 Total wafer per ton Value per ton 7 0.21 Discharged water per ton Recirculated water per ton 32 0.21 Water consumed per ton Do 32 0.25 By States New water Precipitation (30-year average) 43 0.11 Do Price of water 42 -0.11 Recirculated water Precipitation (30-year average) 43 -0.03 Do Price of water 42 - 0.04 Consumed water Precipitation 43 -0.11 New water treated Population density 48 -0.14

Methods for Estimating and Projecting Water Demands for Water-Resources Planning ing basic nutrient requirements in animal feeding are also included. Given the constraints for each producing area, the objective of the model is to find the geographical distribution of agricultural production that satisfies the forecast demand for food and fiber at the national level while at the same time minimizing the cost of agricultural production. By means of a given set of assumptions about price support levels, quantities of land under diversion, export levels, consumer demands, and water prices, the various solutions of the model give the level of produc- tion by each agricultural activity, the quantities of water and land used productively, and the marginal values of water and land in use, for each region. The results so obtained have been primarily used to provide indications of relative changes in demand that might be anticipated under alternative futures. In order to evaluate the sen- sitivity of water use in irrigated agriculture to the price changes of water, the prices of water that are paid by agricultural producers in the model were increased sys- tematically above the prices charged by the Bureau of Reclamation in different water-supply regions. Prices of $15, $22.5D, and $40 per acre-foot were evaluated where they were higher than prevailing prices. The findings appear to indicate that the demands for water in the water-short areas of the West could be relatively insensi- tive to increases in water prices from the prevailing low levels to prices of up to $15 per acre-foot in the water- short areas in the Great Basin, Lower Colorado, Missouri-Arkansas-White-Red, and Texas Gulf. The higher water prices resulted in increased prices for each commodity classification that was studied. If a $40 per acre-foot price of water prevailed, it was estimated that beefprices would be 9 percent higher than they are under present water prices, and the price of wheat was esti- mated to be 10 percent higher. The ultimate effects of such higher farm product prices on retail food prices were not studied. Given the present inflationary trends, this is a crucial issue that cannot long be overlooked. An example of the third approach is that of Duloy and Norton,~5 whose efforts form part of a larger study of the Mexican economy sponsored by the Basic Research Cen- ter of the World Bank. The largest component of the overall modeling effort is a programming model of the Mexican agricultural sector. Possibly the single most striking feature of the submodel is the detailed manner in which the demand for agricultural products is specified. Not only are demand functions for 33 short-cycle crops included at the national level, but import and export estimates are made for 21 of these crops. Prices for com- modities that do not enter foreign trade are determined endogenously, and prices for traded commodities are bounded both above and below by Mexican FOB and CIF prices. The model functions as a market-clearing general-equilibrium system in respect to agricultural commodity production. Duloy and Norton were able to include within their linear programming format both a competitive and noncompetitive market equilibrium. Ag- ricultural markets have typically been competitive; how- 53 ever, the incomes accruing to agricultural enterprises under major changes in output may respond like the incomes that would be experienced by any monopolistic producer. Thus, while agricultural markets are usually characterized by competitive conditions, future national policy may require that some constraints be imposed in this area. WATER DEMANDS IN THE MINERAL INDUSTRIES Water needs of the mineral industries constitute only about 2 percent of water withdrawn by the industrial sector as a whole.~6~7 The largest water-using mineral industries are natural gas processing, phosphate rock, sand and gravel, and iron ore. Kaufman and Nadler carefully analyzed the results of a comprehensive canvass of mineral-industry water use in 1963. This analysis was based on the product-moment method of calculating correlation coefficients. The results are presented as Tables 3.3 and 3.4; r2 is the coefficient of determination, and P is the level of signifi- cance. From Table 3.3 it can be seen that approximately 44 percent of the variation in total water use can be explained by the amount of crude material that was pro- cessed. Kaufman and Nadler further stated: Some 46 percent of the variations in new-water use can be explained by variations in crude material. The remaining 54 percent is assumed to be the result of processing variations. As total water use is the sum of new and recirculated water, the bulk of the effort in the correlation analysis was devoted to these components rather than to the total. This analysis indicated that water availability, as measured by average precipitation or mean stream discharge, is not a use factor insofar as new-water use by the mineral industry is concerned. There does not appear to be a relationship between new-water use and the price of water, although the lack of relationship may result from the type of price data used. The price of water was taken from charges levied by water companies against large industrial users in selected cities for 1955.~8 However, most mineral producers obtain their water from self-operated systems, and therefore the type of cost data used may be completely inapplicable. It is also possible that in many cases the cost of water per ton of ore is such a minor item that cost is not a factor in determining use. In other instances the capital cost of developing a self-operated system is so great, compared with the operating cost, that the total cost per gallon will decline substantially the more water is used. The relative low cost of self-supplied water, particularly in relation to purchased water, is substantiated by data compiled by the Na- tional Association of Manufacturers. ~9 The Association computed that water derived from self-supplied systems would cost be- tween one cent and fifteen cents per 1000 gallons. This would include sources, pumping, treatment and distribution. Water purchased from a utility company would cost between ten and thirty cents per 1000 gallons, exclusive of distribution within the plant. The authors further point out that if it can be assumed that mineral producers are paying $0.15 per 1000 gallons

54 of water, the cost of water as a percentage of the average values per ton of ore would be as follows: New Water Total Water By) (%) Bituminous coal Copper ores Iron ores Phosphate rock Sand and gravel 0.3 .3 1.2 3.9 4.3 1.8 3.0 2.7 3.0 6.7 The figures shown can be considered to be maximums, since many mineral producers do not pay $0.15 per 1000 gallons. Except for the very large user such as the phos- phate rock industry, or an extremely low-value product such as sand and gravel, the cost of water cannot be seen as a significant item. A general assumption can be made that the cost of recirculated water is lower than the cost of new water. Therefore the proportion of average value contributed by total water costs is most likely to be less than indicated by the foregoing data. This tends to bear out Me lack of statistical correlation between water intake and prices. From the foregoing it can be inferred that statistical demand functions for water, as they are gen- erally understood, essentially do not exist for the mineral industry. INDUSTRIAL WATER DEMANDS The factors affecting industrial water demands for a number of industries have been dealt with in some detail by Bower.20 2~ Bower formulates conceptually a joint func- tion governing industrial water demand as follows: QIbQD6C t,QEt,WDt,WEt = where PP L OR poqr R S f(Q t,q t,T,PP,L,OR, poqr,R,S, E c,A ,, Q dt,q dt,~, C U,./C t Qt and At are the quantity and quality and their cor- responding time patterns of water available at the intake; is the water- and waste-treatment processes within the production unit; is the technology of the production process; is the physical layout of the plant; is the operating rate; is the product output quality requirements; is the degree of recirculation; is the solid wastes from the production process; is the limitations on the final liquid effluent; is the limitations on the final gaseous ef- fluent; Qua and qua are We quantity and quality and their corresponding time patterns of water avail- able for dilution at the effluent point; is the availability of places for final disposal of wastes; and is the ratio of total water utilization costs to total production costs. EVERARD M. LOFTING and H. CRAIG DAVIS Bower emphasizes that a forecast of industrial water demand for a particular industry must include the amount of water required for all uses explicitly process, boiler feed, cooling and condensing, and sanitary uses. Because of increasing concern over thermal pollution, a separate consideration of cooling and condensing uses is stressed. These include product cooling, equipment cooling, and condensing in steam electric power generation. Bower summarizes20: Essential to any effort to forecast industrial water demand is an economic base study which includes projections of demands for the product outputs of Me various heavy water-using indus- tries.... Given an economic base study, forecasting industrial water demand involves the following five steps: (1) Classifying existing plants by process, region, product mix, and size; '(2) Forecasting trends and production processes, product mix, and regional location patterns, i.e., forecasting technology; (3) Relating the production process-product mix combinations to gross water applied and waste loads generated; (4) Analyzing the alternative internal water utilization pat- terns and costs thereof, considering the impacts of in-plant water quality requirements in relation to product quality and the costs of other factor inputs such as fuel and heat exchanges; and (5) Forecasting political decisions relating to pricing policy for water at the intakes and policies relating to waste discharges. Given (3) and (4), and the water environment (5), water demand can Men be forecast. In view of the waste-assimilation properties of water, the effect of waste-discharge control on water intake should also be stressed in industrial water-demand fore- casting. Russell, using mathematical programming techniques, developed a model of typical refinery operations that could portray the withdrawal demand for water as a func- tion of intake price and also effluent charges.22 The Na- tional Water Commission staff summarized the results of the Russell model as follows: 1. A petroleum refinery's water withdrawals are sensi- tive to the price of withdrawals and may be reduced by as much as 95 percent if the withdrawal charge goes above 2 cents per 1000 gallons. If the price is raised further, the refinery will be able to reduce water withdrawal further by in-plant recirculation. 2. Discharges of biological oxygen demand (BOD) ma- terials by petroleum refineries are sensitive to effluent charges. An effluent charge of about 2 cents per pound of BOD material discharged may be approximately the tax that would induce a BOD waste reduction of 5~65 per- cent, depending on the technology of the plant. 3. The costs incurred by the petroleum refinery (and presumably passed on to the consumer) for reducing discharges of BOD material are comparable with the costs of developing sufficient additional flow to dilute the discharges. 4. The overall effect of BOD effluent standards on the

Methods for Estimating and Projecting Water Demands for Water-Resources Planning final gasoline price at the refinery might be about one fiftieth of a cent per gallon. 5. Effluent charges or standards directed at curbing the discharge of one type of residual, or pollutant, could have important effects on the discharge of other wastes. In a refinery of the type studied, the quantities of phenols discharged would also be reduced as the discharge of BOD wastes is reduced in response to a BOD discharge tax. Although these results imply that petroleum refineries are sensitive to intake water prices and effluent charges, the 1972 Census of Manufactures (1973 data)23 shows that refinery intake from all sources was 1278 billion gallons with 635 billion being freshwater. Of this amount of freshwater, 132 billion gallons, or 21 percent, was from public supplies with the balance being self-supplied. Data on effluents show that refineries discharged 1155 billion gallons of water during the year, of which 463 billion gallons, or 40 percent, were untreated. Refineries are undoubtedly sensitive to the price of withdrawals given the fact that they can and do supply their own needs well below one cent per 1000 gallons as estimated in the National Association of Manufacturers.24 As the price of publicly supplied water is increased they may opt for developing their own systems. This helps to explain the problem of "block pricing" as noted by Bower25: . . . it should be noted that in many cases rate structures for industrial water users encourage high water intake per unit of product. Generally, large consumers receive lower rates for using more water~.e., the more water used, the lower the price per 1000 gallons. In such situations it often becomes less expen- sive for the industrial user to discharge once used water Man to adopt recirculation. As matters stand, there appears to be no clear-cut method of empirically deriving and projecting demand functions for industrial water use. In contrast to agricul- ture, reliance on water prices and pricing policies for both withdrawals and discharges seems to have been too tenu- ous an instrument for achieving the desired goal of dramatically reducing water demands and wastewater discharges. Only 11 percent of industrial water in 1973 was publicly supplied and thus subject to price increases as a matter of policy. This is in contrast to the 50 percent of industrial water drawn from public supplies in 1950.26 Furthermore, only 60 percent of discharges were treated in 1973. The requirement of Public Law 92-500 can be expected to bring more dramatic changes to industrial water demands than have been evident over the past few decades. Historical water intake data are given in Table 3.5. The National Commission on Water Quality report states27: Several technological solutions for both 1977 and 1983 limita- hor~s are founded upon reduction in water use or by-product 55 TABLE 3.5 Historical Gross and Intake Water Usage by All Manufacturing Industriesa Year Gross Water Used (billions of gallons) Net Water Intake (billions of gallons) 1959 1964 1968 1973 26,257 29,857 35,701 46,965 12,131 14,007 15,467 15,024 aSource Plater Use in Manufactunng,' Census of Manufactures, Bureau of the Census, 1961, 1966, 1971, 1975. recovery. These options are likely to have wider application for BAT [best available technology] than for BPT [best practicable technology]. The full potential for such approaches is unde- veloped, but they will probably become more prevalent as limi- tations become more stringent and technologies for treating large wastewater volumes become more expensive. In general, the Commission on Water Quality submits the data in Figure 3.1 to show overall industry respon- siveness to price changes in water and cost increases in waste discharge. The price elasticity of demand for industrial water intake as given can be used as a guide for estimating future withdrawal demands in limited instances. THERMOELECTRIC POWER WATER DEMAND Steam electric generating stations primarily use water for cooling. The amount of cooling water withdrawn per kilowatt-hour generated is governed by the type of plant, the thermal efficiency, the number of degrees over which the intake water is heated (this is termed the "range"), and the method of cooling that is used. The amount of water used in steam electric power generation in the United States is now greater than irrigation water with- drawals.28 It accounts for somewhat more Man 40 percent of all water withdrawn. Water used consump- tively, that is evaporated or lost in the cooling process, is only about 1 percent of total intake at the present time. A typical "range" for a plant using once-~rough cool- ing is 15°F. This means that each gallon used absorbs 125 Btu of waste heat.29 On this basis, some 43 gallons of cooling water are circulated per kilowatt-hour generated in thermal plants, and about one half gallon (1 percent) of this water is ultimately evaporated.30 Table 3.6 provides estimates of water withdrawals and consumption for the years 198(}2020 for thermal electric generating facilities.3~ These estimates assume minimal increases in plant efficiency and once-through cooling practice. The assumptions, although termed unrealistic by the National Water Commission staff, afford an upper bound for withdrawal and consumptive uses based on projected growth of thermal generating facilities. The values shown in the table indicate that the withdrawal needs for condenser cooling will be approximately equal

56 IF: Price of water I oh | increases L PRICE OF WATER _ TH EN: _ Water intake volume decreases 4:,.'~ 0.7% for chemicals 1.4% Paper 4 ,. :~,'.-.] 1.4% Petroleum Am: .; A. . A; 4~ 1.6 as Stee I COST OF WATER cost of effluent discharge volume of effluent discharge IF , . . . combined water 1% ~ sewer f low charge increases Suspended solids ~ | chargeincreases '%L Biochemical I oxygen demand I% charge increases SOD charge 1'~ | increases L THEN: Flow decreases 4~1.4% SS concentration decreases _ ~0.7°70 BOO concentration decreases 40.2S1 % BOO volume decreases 30.1% FIGURE 3.1 Industry responsiveness to cost of intake water and waste discharge. to the average annual runoff of the United States by the year 2000. The consumptive use is only slightly more than 1 percent of withdrawals, however. In order to place the projected thermal energy demands in perspective and assess some overall means of bringing the associated water needs into balance with available supplies, two avenues have been investigated: (1) the reduction in overall electrical energy demand and (2) the means for the direct reduction in water withdrawals. (1) An analysis of socioeconomic data for the period 1955-1969 indicates that electric power consumption plus losses and in-plant uses can be statistically corre- lated with population, Gross National Product, electricity prices, and gas prices.32 The Bureau of Economic Analysis, United States De- partment of Commerce, has made high, medium, and low projections of Gross National Product to the target year 2020. These were based on the B. C, and D population TABLE 3.6 Sample Projections of Total Water With- drawals and Consumption for Thermal Electricity Gener- ation (billion gallons per day) 1980 2000 2020 Withdrawn 330 Consumed 3.8 EVERARD M. LOFTING and H. CRAIG DAVIS growth rates of the Bureau of the Census.33 These growth rates were then used in a regression model to project electric power needs. A fourth projection was based on a low growth rate combined with a 50 percent increase in electricity prices. The four resulting projections of cool- ing water are presented in Figure 3.2. These projections of freshwater withdrawals assume no technological change and no recirculation. The relation between the price of electricity and cooling-water withdrawals has also been studied. The analysis showed that a 50 percent increase in We price of electricity would result in a 27 percent decline in cooling-water withdrawals. There appears to be some indication that We demand for electricity is related nega- tively to increases in price. An analysis by Wilson34 shows that regional power demands may have an elasticity greater than 2, which would mean that a 10 percent increase in price would cause a 20 percent fall in energy use. It is felt that some of this decline would be due to We relocation of energy-intensive industries to other areas where energy rates may be lower. On such evidence, it appears that pricing policies could be used to influence electricity use and thus cooling-water use. The analysis, however, does not distinguish between We industry demands and consumer demands. In fact, energy studies at the Center for Advanced Computation, University of Illinois, have shown that approximately 65 percent of all energy demands are interindustry demands. For electrical energy only, the proportion may be closer to 55 percent in interindustry demands.35 If estimates of 4000 Or 1000 ~ 1072 2297 12.5 26.7 3000 2000 HIG H 199 0 LOW GROWTH- HIGH COST 2000 2010 2020 FIGURE 3.2 Projections of freshwater withdrawals for electric- ity generation under different economic growth rates.

Methods for Estimating and Projecting Water Demands for Water-Resources Planning reductions in electricity demand are calculated in such an aggregate manner, the possibilities for "self-supplied" electrical energy are masked. An important problem raised by the research staff of the Electric Power Re- search Institute relates to the setting of power prices so that large users will continue to purchase "blocks" from utilities rather than develop their own generating capacity an option available to a number of industries. The foregoing analysis gives no indication which sector (industrial or household) of the economy is affected and the manner in which the reductions may occur. (2) A potential way to reduce cooling-water withdraw- als might be to raise the price of water itself. However, if the price of cooling water is increased, utilities may recir- culate the cooling water several times rather than use a "once-through" cooling process. If this is done, then the temperature ofthe cooling water is raised and evaporative (consumptive) losses are substantially greater.36 Less water is returned to the natural water course for other downstream users, and thermal pollution problems are increased. Thus, increasing the price of cooling water may result in changing withdrawal demands into con- sumptive demands and an overall depletion of available . . . . supp les In a given per~oc . It is conceivable that different prices might be levied for withdrawing freshwater and also for using it consump- tively. Basically, in order to keep the consumptive use of water at low levels, the only possible alternatives are to use once-through cooling or, at higher water prices, to use dry towers.36 However, the National Water Commission staff estimated that water prices greater than $1400 per million gallons consumed would have to be charged to induce plants to limit their water consumption to the zero level, given the capital cost of dry tower technology. In the overall, freshwater withdrawals by steam- electric generating stations might be influenced by set- ting water prices at levels that could only be considered unreasonable in the present economy. The consumptive use of water by thermal plants appears to be insensitive to price changes within what might be considered a reason- able price range. It should be stressed, nevertheless, that pricing withdrawals of freshwater for thermal plant cool- ing has not yet been tried and may be limited in practice. The response of regulated utility companies to increases in costs is very different from the response of nonregu- lated industries. Thus, changes in the price of water may in fact have little or no effect on demand. The consump- tive use of freshwater for cooling is virtually insensitive to price changes for water within any realistic price range. COMMERCIAL DEMANDS FOR WATER The definition of commercial water use by water-supply agencies is probably less rigorous than for any other category. In the alignment scheme presented earlier in this paper in Table 3.2, the commercial sector can be accurately defined as Standard Industrial Classification 57 (sic) groups 50 through 89, excluding major group 88— Private Households.37 Demand functions for water use in the trade and ser- vice sectors of the economy are needed; however, only rather fragmentary data appear to have been accumulated and analyzed. Howe reported on these in 1968.38 One of the points not dealt with by Howe, but mentioned in an earlier section of the present paper, is the fact that many water-supply agencies may classify multiple-unit dwell- ings as commercial users. Thus, the water supply to apartment houses that are clearly residential or household in nature may be classified as a commercial end-use by the agency. This may tend to skew badly the results of any study. Moreover, many trade and service establishments have the option of self-supplied water systems, which may further tend to limit the validity of the results based solely on an analysis of water-agency data, which reflect supplies to a broad category of users termed "commer- cial." For analytical purposes, overall water-agency data from selected cities may need to be modified in order to account for the total amount of household intake and the possible misclassification of light industry or other man- ufacturing establishments to the category of commercial users. At present, specific price elasticity of demand functions for water used in the various trade and service sectors of the U.S. economy have not been estimated. HOUSEHOLD (RESIDENTIAL) WATER DEMANDS Water withdrawals for household use in 1975 amounted to approximately 23.6 billion gallons per day, of which about 91 percent, or 21.5 billion gallons per day, were furnished by municipal water systems. }7 Household water needs are typically divided into two categories: in-house uses and lawn sprinkling. The major in-house uses are drinking and cooking, 5 percent; dishwashing and laun- dry, 20 percent; bathing and personal use, 30 percent; toilet flushing, 45 percent.39 For single-family dwellings, lawn-sprinkling uses amount to more than 50 percent of the total yearly use. Howe and Linaweaver statistically analyzed the effects of density, property value, geo- graphical location, and water price on household de- mands.40 Both in-house and lawn-sprinkling uses have been found to be responsive to changes in water prices; Table 3.7 shows average commercial water-use data in metered and flat-rate areas.39 Howe and Linaweaver determined the important vari- ables governing water use for sprinkling in areas that are metered were water price, dwelling unit value, and pre- cipitation. For flat-rate areas, the governing variable was dwelling unit value. Demands for in-house uses were determined to be less responsive to price and income changes than those for sprinkling. Using the Howe and Linaweaver data, a Resources for the Future report for the National Water Commission

58 TABLE 3.7 Average Annual Water Use in Metered and Flat-Rate Areas Gal/day per Dwelling Unit Metered Areas Flat-Rate Areas Leakage In-house Sprinkling TOTAL Maximum Day Peak Hour 25 247 186 458 979 2481 36 236 420 692 2354 5170 projected household needs to 1990.4° Under different assumptions of price and population growth, it was ar- gued that the growth of population alone has a greater impact on water use than the spatial expansion of urban areas, and further, the price of water has a much greater impact than either of the two preceding variables. In summarizing, it can be noted that the theory of consumer demand truly comes into its own in the analysis of residential water use. The demand functions were well behaved in all cases studied. The data indicate that lawn sprinkling accounts for more than 50 percent of average annual use for single-family dwellings. The amount of sprinkling water used decreases with price increases. This is less striking in the western United States than in the East. The amount of water used for in-house purposes is approximately the same regardless of the price charged for the water. USE OF DE MAND FUNCTIONS IN WATER- RESOURCES SYSTEMS PLANNING The term "water-resources systems" can be used to en- compass the large-scale impoundments and conveyance systems typical of the Tennessee Valley Authority and the Bonneville Power Administration and the smaller pump- ing, storage, and distribution systems of many metropoli- tan areas. Historically, in the United States many of these systems were developed on the basis of engineering feasibility studies and certain multipurpose objectives, such as hydra power generation, flood control, land rec- lamation, and navigation, along with water supply. Many of the nation's largest multipurpose water-resource sys- tems were planned and developed after 1930 when the federal government indirectly assumed an increased re- sponsibility for the use of water resources. Most, if not all, of these large projects were begun as part of the major public works programs typical of the 1930's.4t Several decades earlier, the Reclamation Act of 1902 had been passed to stimulate and consolidate the westward expan- sion that followed the development of the transcontinen- tal rail lines. By 1929, about 19 million acres were irri- EVERARD M. LOFTING and H. CRAIG DAVIS gated,42 although only about 7.5 percent were directly controlled by the Bureau of Reclamation. At present, attention is focused on the rather striking amounts of water that have been developed by means of federal projects, the rather modest prices that are charged for water, and what the past trend augurs for the future. It is felt that if water prices are permitted to rise on the basis of the value the water would have in alternative uses, or are increased as a matter of public policy, then users would presumably carefully monitor their withdrawals to minimize costs and thus substantially reduce overall water use in the economy. If this occurs, new projects can be postponed or possibly deferred indefinitely. This would permit substantial sums of money, tentatively allo- cated to proposed projects, to be reallocated to other pressing national needs. These considerations are obvi- ously at the root of the demand versus requirements Issue. In the earlier sections of this paper, the potential for developing statistical demand curves for each major cate- gory of water use was explored. In light of the findings, it seems feasible that water-demand functions for irrigation water can be developed, using either statistical analysis or mathematical programming techniques, and applied in water-resources systems planning. For the mineral indus- tries and certain industries that are heavy users of water, the prospects for developing and using statistical demand functions in systems planning appear to have been over- shadowed by changes in the Water Pollution Control Act passed by Congress in 1972. The stipulations of the Act will bring to the fore some minimal technological level of water use to meet discharge standards regardless of intake price. The best achievable technology (BAT) should carry with it some minimal level of in-plant use of water for all industries. If the provisions of the Act are enforced, water price should have little influence on demand in the future for those classes of industries that have traditionally been termed "water intensive." For the trade and service sectors and those light indus- tries where water use is limited to sanitary, air condition- ing, and boiler feed uses, and certainly for residential and household needs, the development and use of water- demand functions should play a major role in water- resource systems planning in the future. Such applica- tions will probably find more immediate use in the planning of metropolitan water-supply systems than in any large multipurpose project in which water supply is coupled with flood protection or other water-related considerations. THE ROLE OF WATER-USE INFORMATION IN FORECASTING FUTURE WATER DE MAND S Official water-use data are compiled and published by several federal agencies. Additionally, there are special

Methods for Estimating and Projecting Water Demands for Water-Resources Planning studies funded by federal, state, and local governments as needs arise. Official data sources: 1. United States Geological Survey, "Estimated Use of Water in the United States," quinquennially since 1950.28,43-46 2. United States Water Resources Council. National Water Assessment Studies, by decades beginning in 1965 ~7 47 3. Census of Agriculture, United States Bureau of the Census. Irrigation and Drainage on Farms.48 4. Census of Mineral Industries, United States Bureau of the Census. "Water Use in Mineral Industries," Eco- nomic Census years 1954, 1963, 1967, i972.49-52 5. Census of Manufactures, United States Bureau of the Census. Water Use in Manufacturing. Economic Cen- sus years 1954, 1958, i964, 1968, 1973.53-57 6. United States Army Engineers Permit data, 1971, unpublished.58 The United States Geological Survey (USGS) data pro- vide water use by major categories for the United States, the 50 states, and water-use regions. The data are related to population and acreage. A bibliography of primary data sources is given in the USGS publications. The United States Water Resources Council provides base-year data, principally following the USGS categories, and furnishes projections at 10-, 15-, or 20-year intervals. The data as presented are not related to measures of production. The Census of Agriculture includes data on drainage basins, land irrigated, crop production on irrigated land, water conveyed, users, and types of organizations. The Census of Mineral Industries and Census of Man- ufactures water data are furnished for detailed categories of end-use and are related to establishment, employment, value added, and value of shipments for the United States, the 50 states, and regions. The Army Engineers Permit data relate water use to employment and value of product for specific dischargers. At the state and regional levels, the Census data be- come sketchy because of disclosure problems; however, they can be made usable with some statistical effort. As resource scarcities, particularly water, have become increasingly evident in the United States, the need for estimating future demands in some standardized manner has been apparent. The sources of supply are regional in nature, as are the elements of demand. If forecasting techniques are not standard and uniformly applicable to any of various geographical regions, estimates of supply and demand may tend to embody broader interregional political considerations rather than the objective realities of regional resource availabilities. Water-resource de- velopment, transfer, and distribution systems are usually capital-intensive and may take as long as a quarter of a century from conception to water delivery for major proj- ects. Over the decades, this has led planners to perhaps 59 wish to err on the side of recommending excessive re- finement in projection techniques rather than be guilty of overbuilding. If, of course, it can be successfully argued that the benefit-cost ratio of obtaining better data for planning purposes at any level is not greater than one, then the concern over detail is not a valid one. Nonethe- less, the dilemma for planners is real. If they are conser- vative in planning irrigation projects, the basic objective of adequate food supplies is defeated by shortfalls in production and high prices. If they are liberal in their projections, unused facilities and surplus productive ca- pacity bring on not only agriculture surplus problems but also a loss of public confidence. In order to project future water demands in a stan- dardized fashion for a region, a series of regions, and ultimately the nation, a multisector economic framework should be established for some base year. Such a framework permits region-by-region comparisons to be made objectively. Economic activity projections can be made by region in constant dollar terms to the specified target years from the base year. The finer the industry detail, and the water-use detail available by specific pur- pose for the base year, the more comfortable one might feel that errors might tend to be in a conservative direc- tion. As the time span of the projection is increased, the likelihood lessens for a detailed product mix or perhaps even the industry mix to be maintained in any specified proportions for a given economic region. Projections, of necessity, have to be made in a more aggregate format as the time span from the base year increases. Once the given set of industry projections in constant dollars has been made, the base-year water-use information can be modified in the light of modeling techniques that include demand elasticity considerations, where they are appli- cable, and technological considerations for those sectors where these seem to be the governing factor, i.e., where thermoelectric cooling may be involved. The base-year water-use information should also in- clude data on self-supplied or publicly supplied water. Consideration should be given in the economic projec- tions to the practice the various industries in the region will be expected to follow in regard to sources of supply throughout the time span under consideration. When dealing with economic variables, there tends to be a cer- tain stability exhibited by aggregates and their projection despite marked changes in their underlying components. A relevant example that can be cited is the water-use fore- casts made by the staff of the Paley Commission in 195226 shown in Table 3.8. Based on the water-use information available in 1950, a forecast of requirements for 1975 was made. The estimate for 1975 was some 4 percent lower than the 1975 figures provided by the United States Water Resources Council,~7 despite substantial changes in product output beyond those forecast in detail by the Commission. Although the period 1975 to 1985 should bring major changes in the pattern of water use, once new technology is adopted, it is reasonable to speculate that longer-term

60 EVERARD M. LOFTING a net H. CRAIG DAVIS TABLE 3.8 Estimated Total Withdrawals and Requirements for Water 1950 and 1975 Estimated with- drawals, 1950 Billion Gallons per Day Estimated Require- ments, 1975 Billion Gallons per Day Percent of Total Increase, 195~1975 Billion Gallons per Day Percent of Total Percent Increase Municipal and rurala 17 9 25 7 8 50 Direct industrial 80b 43 215 62 135 170 Irrigation 88 48 110 31 22 25 TOTAL 185 100 350 100 165 ~5 aRoughly half of total municipal supplies are used industrially. Includes an estimated 15 billion gallons per day of salt water used in industry for cooling. projections of the rate of growth of withdrawal demand may stabilize at some markedly lower intake value. Be- cause of recirculation and reuse, consumptive demands may rise substantially during the same period. In earlier sections of this paper it has been noted that demand functions can be estimated statistically for most consumer goods. It has also been pointed out that large- scale multisector programming models have been used in certain instances to estimate demand functions for water for the agricultural and industrial sectors of the economy. Given the marked changes in water use that may occur in various sectors under the stimulus of water-pollution con- trol measures, it seems unlikely that a high degree of reliability should be attached to demand functions for water based on current data. For the agricultural and industrial sectors of the economy, the forecasting of future water demands may be greatly improved by implement- ing a series of detailed process analysis studies to deter- mine the required minimum amounts of water that will be necessary for these sectors to function efficiently under adverse conditions. Placing too great a reliance on the concept of market supply and demand functions as op- posed to gaining a comprehensive understanding of the technological possibilities for reducing resource inputs may be an error. The entire discussion of deriving market supply and demand functions should be leavened with the critical comments of some detractors. Leontief59 has given some insight into the problems relating to the derivation of demand functions: As objects of empirical analysis the market supply and demand functions [have] proved to be singularly elusive. They cannot be observed directly and most attempts to derive them through methods of indirect statistical inference have yielded with a few notable exceptions- disappointing results. The principal difficulty lies in the great instability of the observed price quantity relationships and this instability can be shown to be inherent in the internal logic of the general equilibrium system itself. Within the framework of such a system each structural relationship is by definition independent of all the (structural or non-structural) relationships. Every price and every quantity produced or consumed is on the contrary- by the theoretical general equilibrium hypothesis expected to depend simulta- neously on all the structural relationships. This means that, if the hypothesis as applied to an observed system is correct, the dependent variations of each price and quantity would necessar- ily reflect the autonomous changes of all the basic structural relationships and, what is more important, these variations will be distributed in such a way that a statistical determination of the unknown shapes of the corresponding Walrasian demand anal supply equations would practically be impossible. Boulding and Spivey have spoken to the same problem within the broader framework of the theory of the firm60: A theory which assumes knowledge of what cannot be known is clearly defective as a guide to actual behavior. What must be known, however, . . . is a whole set of functional relationships, such as demand and supply functions, which are not given by immediate experience, and often are not even given by Me most refined analysis of past data. Theoretical demand functions for the industrial sector should thus be seen as useful heuristic devices. For empirical research they provide an overall framework for structuring the various components of water-use informa- tion. IMPACT OF CLIMATIC VARIABILITY AND CHANGE TO FORECASTING DEMANDS Currently there appears to be no firm consensus regard- ing the magnitude or direction of fixture climatic change. There is geological evidence that such changes could occur relatively rapidly 50 to 100 years and that the impacts might possibly have catastrophic consequences in terms of human conditions.6i Translating the impacts of climatic variability and change into certain direct effects on regional and national water demands can, at best, involve only the grossest assumptions as matters stand. A general warming trend in the United States climate could translate into increases in evaporative losses, low- ered efficiencies in cooling for all major purposes, in- creased use of water for air conditioning, and presumably some decreases in boiler feed water for heating. If a

Methods for Estimating and Projecting Water Demands for Water-Resources Planning general cooling trend were to be experienced, then evaporative losses would be decreased, cooling efficien- cies may be increased slightly, air-conditioning uses would decline, and boiler feed-water use should increase. Quantifying these changes in response to the expected climatic changes would require a detailed modeling ef- fort. The impacts of climatic variability in terms of worldwide and local droughts will have both direct and indirect impacts on U.S. agriculture, which may over- whelm the other aspects of water-demand changes. Winstanley et al.,62 Winski,63 and Alexander64 summarize predictions that indicate that by the year 2000 the preven- tion of starvation may be the main global concern. This view is not by any means entirely acceptable to many agriculturalists or water planners. On balance, agricul- turalists have acknowledged this possibility; however, in the face of past agricultural surpluses in the United States it has not been considered a fruitful avenue of research. One can cite, for example, the typical comments in a text by Barlowe65: Winstanley et al. 62 state, nevertheless: Probably the most serious problem facing the world concerns our ability to meet the increasing demand for food. At least one and a half billion people are chronically mar-nourished (Erlich and Erlich 1972~66 and it has been estimated that 1~20 million people die every year directly or indirectly from lack of food (Dumont and Rosier 1969~.67 These figures are for an average year, and do not reflect the situation in times of drought or other calamities (U.N. 1974~.68 Last year some ten million people in the Sahel Zone of Africa were on the brink of starvation, and 100,000 people in Ethiopia died from starvation. Hunger is closely corre- lated with poverty and bow lead to social and political instabil- ity: within the last twelve months there have been political upheavals in the drought-affected countries of Ethiopia, Upper Volta, and Niger, and serious food riots in India. Food production must be doubled in about thirty years to meet the projected demand—and it has taken at least ten thousand years to attain the present level of production. The U.N. (1974~68 has identified the effect of recent adverse weather conditions on crop production as one of the major factors in the present world food crisis. World grain reserves now represent less than a month's food supply for the world and there is no longer any idle agricultural land in the U. S. A. to act as a reserve. There is a real threat that crop failures would lead to widespread starvation. Evidence is accumulating which shows that the climates of the Earth are changing, and it has been suggested Mat they might be changing in a direction which could have a net adverse effect on world food production, and global economic and political stabil- ity (I.F.I.A.S. 197469; Rockefeller Foundation 19747°). Probably the main reason for irrigating and draining the land is to increase food production and one of the main factors detennin- ing the need for irrigation and drainage is climate. If the Winstanley, Alexander, and Winski summary prospects are borne out, then planners may possibly have to reconsider the extent to which irrigable lands will play a preponderant role in the future, and present projections may have to be revised. Alexander cites Reid Bryson, who 61 contends that the monsoons may probably not return with regularity to regions such as northern India during the remainder of this century. If this is correct, the prospect looms that even the present populations of the monsoon belts could not be maintained even if all the arable. land in the rest of the world were placed in full production for this period. Because of the unusual and irregular way in which the global weather changes are beginning to man- ifest themselves, there is some evidence that a return of heavier rainfall in the western plains and Rocky Moun- tain states may not be unusual. Settlers who traveled to California left accounts that one of the hazards of crossing the plains was the possibility of losing sight of the main party because of endless stretches of head-high grass that grew in regions that are almost desert at the present time. Bryson speculates that the change in climate might possi- bly have played a greater role than hunters in the disap- pearance of the huge herds of bison. If the heavier rain- falls in the western United States were to occur, then possibly certain proposed irrigation projects might have major flood-control benefits. On the other hand, Winstanley has noted that if the weather patterns in Africa persist they may shift the entire Sahara Desert southward; and efforts to halt such climatological encroachments by, for example, planting windbreaks or increasing irrigation would be in vain. In the Soviet Union, for example, a third of the grain crop comes from the drought-prone virgin lands of Siberia, and consideration has been given to diverting some of the great Siberian rivers into large irrigation projects. These rivers empty into the Arctic Ocean, where the less-dense freshwater spreads out on top of the salt water and thus permits the Arctic Ocean to freeze over. According to some experiments by a Russian scientist, O. A. Drozdov, and a British meteorologist, R. L. Newson, who have constructed a mathematical model of wind patterns in the northern hemisphere, the consequence of inhibiting the freezing of the Arctic Ocean may be to cause winters to become colder and drier over many continental areas at the middle latitudes. Some prominent Soviet meteorologists have expressed concern over these propo- sals. However, if disastrous, protracted droughts were to occur in the Siberian wheatlands, Soviet planning au- thorities might feel that there would be little to lose in proceeding with these projects. In the United States and Canada such proposals as the North American Water and Power Alliance schemes called for diverting rivers like the MacKenzie, which flows northward into the Arctic Ocean and through large impoundment and conveyance structures carrying these waters southward into the United States for irrigation and power-generating pur- poses. Such engineering schemes could possibly have impacts similar to those of the proposed diversions in the Soviet Union. If droughts were to persist, possibly these schemes, or some variant, might be given consideration in order to increase worldwide food supplies. In order to place the question of increased irrigation demands in perspective, assuming that increased food

62 EVERARD M. LOFTING and H. CRAIG DAVIS TABLE 3.9 Land Utilization, Farm and Nonfarm: 194(}1969 (in millions of acres, except percents. Prior to 1950, excludes Alaska and Hawaiia 1940 Major Use 1950 Land Percent 1959 Land Percent 1964 Land Percent 2271 100.0 Land Percent 1969 Land Percent Total land area 100.0 2273 100.0 100.0 2264 100.0 In farms 1061 55.7 1162 51.1 1124 49.5 1110 49.0 1064 47.0 Croplandb 399 20.9 409 18.0 392 17.3 387 17.1 384 17.0 Grassland pastures 461 24.2 486 21.4 532 23.4 547 24.1 540 23.9 Woodland pastured 100 5.2 135 5.9 93 4.1 82 3.6 62 2.7, Woodland not pastured 57 3.0 86 3.8 70 3.1 64 2.8 50 2.2 Farmsteads, roads, and other land 44 2.3 46 2.0 37 1.6 30 1.3 28 1.2 Not in farms Grazing lands Forest land not grazede Other landf 844 44.3 504 26.4 203 10.7 137 7.2 1111 48.9 1 402 17.7 368 16.2. 341 15.0 147 50.5 1156 51.0 1200 53.0 319 14.0 293 12.9 288 12.7 438 19.3 443 19.5 475 21.0 390 17.2 420 18.5 437 19.3 aSource: U.S. Dept. of Agriculture, Economic Research Service. In Agricultural Statistics, annual. DCompnses cropland used for crops, soil improvement crops, and idle cropland. Includes cropland used only for pasture. Includes grassland, and woodland, and shrub and other forested land grazed. eExcludes forest areas in parks and most other special uses. fCompnses urban, industrial, and residential areas; rural parks; wildlife refuges; highway, road, and railroad nghts-of-way; ungraded desert; rocky, barren, swamp, tundra, and other land not otherwise counted. production requires this, land-use patterns and trends are given for the United States (Table 3.9~. Irrigated acreage data are given in Table 3.10. It should be noted that these data are provided for the 17 western states only. Federal irrigation projects data are provided in Table 3.11. In April 1974, the Water Resources Council released the new Series E Population OBERS projections showing an 18 percent decrease in cropland harvested by the year 2020 (Table 3.12~. In May 1975, a revised series of ag- ricultural projections (Series E') was released, which showed a 15 percent increase in cropland harvested by the year 2020 (Table 3.131. The revisions have been attributed to more recent assessments of the domestic and foreign supply-demand relationships. Figure 3.3 has been reproduced from Winstanley et. al.62 If the United States should wish to assume a posture in which the food deficits of the so-called "Baird World" countries can be met by the agricultural production of the United States and other developed countries, then further revisions of the projections of irrigated cropland may be in order. 1 WATER-USE FORECASTS FOR 2000 AND 2020 Projections of water withdrawals and consumptive use to the years 2000 and 2020 were made by the United States Water Resources Council in 196847 and by Wollman and TABLE 3.10 Irrigation of Agricultural Land Summary: 192~1969 EData are for 17 Western States (Alaska and Hawaii excluded) and Louisiana, except as notedia Item 1920 1930 1940 1950 1959 1969 19690 Approximate land area milt acres 1190 119~) 1191 1191 1189 1187 2263 Farms, total 1,000 1684 1820 1681 1430 1044 854 2730 Irrigated 1,000 222 264 290 289 267 210 257 Land in farms, total milt acres 488 553 611 699 715 733 1063 In irrigated farms milt acres c 78 112 168 213 218 237 Land irrigated, total milt acres c 14 18 25 31 35 39 Irrigation organizations: ~ O _ Number 1,000 c 4 6 10 9 8 8 Area irrigated milt acres 12 13 14 15 18 21 21 Investment from prior census year milt dol. c 162 160 520 1040 1591 1607 aSource: U.S. Bureau of the Census, U.S. Census of Agriculture: 1930, 1940, 1950, 1959, and 1969, Irrigation of Agricultural Lands. Data are for all states in the U.S. CComparable data not available.

Methodsfor Estimating and Projecting Water Demands for Water-Resources Planning TABLE 3.11 Federal Irrigation Projects: 195(}1971 (Acreage in thousands; value in $ millions Supplemental and Temporary Entire Area Full Irrigation Servicer Imgation Servicer Gross Gross Gross Irr~gable Irrigated Crop Irugable Irrigated Crop Irngable Irrigated Crop Year Acreage Acreage Value Acreage Acreage Value Acreage Acreage Value . 1950 6025 5071 578 3305 2716 311 2720 2361 267 1955 7368 6262 828 3826 3163 429 3542 3099 399 1960 8171 6900 1158 4326 3488 581 3845 3412 577 1965 9612 8012 1557 4540 3731 675 5072 4281 882 1968 9g04 8387 1840 4683 3940 813 5221 4447 1027 1969 10140 8576 1885 4839 4070 867 5301 4506 1018 1970 10198 8570 1882 4844 4037 847 5354 4533 1035 1971 10560 8834 2124 4853 4050 943 5707 4784 1182 63 aSource: U.S. Bureau of Reclamation, Federal Reclamation Projects, Water and Land Resource Accomplishments, annual. Applies to irrigable land receiving its sole irrigation supply through Bureau of Reclamation-constructed facilities and to previously irrigated land in nonfederal projects where a substantial part of the facilities was constructed, rehabilitated, or replaced by the Bureau. CApplies to irrigable land receiving irrigation water through Bureau projects in addition to supply from nonproject sources and to land for which water is delivered under temporary arrangements. TABLE 3.12 Use of Land Resources, Selected Historical and Projected Years Land in Farmsa 1959 1964 1980 , 195~2020 (in Thousands of Acres) 1985 2000 2020 Cropland Harvested 311,285.2 286,708.1 292,242.6 285,585.4 271,920.4 255,656.1 Feed crops Grainsb 125,395.0 93,658.2 102,936.3 99,795.9 91,147.2 63,016.8 RoughageC 76,432.0 78,829.4 68,787.2 67,446.5 64,396.1 61,862.7 Food crops Grains 52,376.0 51,413.6 43,976.3 42,786.1 40,306.1 37,297.2 Vegetables, fruits, and sugar 8,992.9 9,638.1 9,024.3 9,006.4 9,154.7 9,078.6 Others 3,176.0 2,923.1 3,105.9 3,087.8 2,982.9 2,908.1 Over crops Oil' 26,261.0 33,841.6 53,044.2 52,773.5 52,801.1 51,277.7 Cotton, tobacco, and miscellaneous 22,765.5 21,230.1 14,843.0 14,841.1 14,335.5 13,222.0 - Total crops harvested 315,598.4 291,533.7 295,717.4 289,737.4 275,123.6 258,663.2 Cropland not Harvestedh 136,278.5 147,130.0 165,843.4 172,601.4 186,401.5 202,420.4 Total Cropland 447,563.7 433,838.1 458,086.0 458,186.8 458,321.9 458,076.5 Forest and woodland 163,684.3 145,711.5 105,231.8 102,759.6 95,339.7 86,404.5 Pasture, range, and other lanai 508,909.8 526,323.5 481,566.3 478,927.2 472,341.4 463,098.2 Total land in farms 1,120,157.8 1,105,873.1 1,044,884.1 1,839,873.6 1,025,003.0 1,007,579.2 Irrigated Cropland Harvestedj 27,436.8 29,902.8 36,919.1 36,446.6 36,218.8 36,003.5 Feed crops Grains. 5,255.4 6,585.0 10,196.5 9,975.5 9,581.0 9,495.6 RoughageC 7,483.6 9,144.9 10,581.6 10,557.3 10,983.3 10,932.2 Food crops Grains 2,961.9 3,785.5 4,208.9 4,086.9 3,869.2 3,772.2 Vegetables, fruits, and sugar 3,601.8 4,826.6 5,049.9 5,191.8 5,514.5 5,837.0 Others 1,158.0 1,007.1 1,263.9 1,276.4 1,319.4 1,358.7 Other crops Oil' 395.0 479.8 1,264.1 1,292.4 1,380.3 1,443.5 Cotton, tobacco, and miscellaneous 3,465.0 4,281.2 4,743.6 4,454.6 3,961.8 3,565.8 Total irrigated crops harvestedk 24,320.7 30,110.1 37,308.4 36,835.0 36,609.6 36,405.0 Acreages are exclusive of Alaska and Hawaii. 6~fFootnotes b-f identify the 23 major crops for which acreages were projected; historical values for food account for total acreages of crops harvested. Includes corn, grain sorghum, oats, and barley. qncludes hay and silage. Includes wheat, rye, and rice. CIncludes Irish and sweet potatoes, dry beans, and dry peas. Includes soybeans, peanuts, and flaxseed. Total crops harvested will not equal Cropland harvested because of double cropping. Cropland used only for pasture or grazing, cover, crops, legumes and soil-improvement grasses, crop failure, cultivated summer fallow, and idle land. Land occupied by houses or other buildings, lanes, roads, ditches, land in ponds, and wasteland. Includes acreages for 17 western states, Arkansas, Mississippi, Louisiana, and Florida (1960 acreage reported under 1959 for Arkansas, Mississippi, and Florida). Total irrigated crops harvested will not equal cropland harvested because of double cropping and/or nonreporting. feed, and other crops include acreages of minor crops to

64 EVERARD M. LOFTING a nd H. CRAIG DAVIS TABLE 3.13 Use of Land Resources, Selected Historical and Projected Years, 1959-2020 (in Thousands of Acres) Land in Farmsa 1959 1964 1980 1985 2000 2020 Cropland Harvested 311,285.2 286,708.1 307,624.4 317,000.6 354,270.2 356,423.3 Feed crops Grainsb 125,395.0 93,658.2 96,127.4 98,778.5 113,774.4 111,738.7 Roughage C 76,432.~) 78,829.4 73,664.9 74,524.6 77,485.6 81,086.4 Food crops Grains 52,576.0 51,413.4 51~956.1 50,069.1 49,909.1 49,104.0 Vegetables, fruits, and sugar 8,992.9 9,638.1 9,471.7 9,634.4 9,892.5 10,274.1 Othere 3,176.0 2,923.1 2,922.7 2,869.0 2,708.3 2,678.8 Over crops Oily 26,261.0 33,841.4 61,488.4 69,483.9 88,486.0 88,908.2 Cotton, tobacco, and miscellaneous 22,765.5 21,230.1 16,355.0 16;,3()7.5 16,319.9 16,934.9 Total crops harvested 315,598.4 291,533.7 311,286.7 32l,66S.9 358,575.7 360,725.1 Cropland not Harvestedh 136,278.5 147,130.0 150,510.3 141,166.2 104,(~51.8 101,653.2 Toad Cropland 447,563.7 433,838.1 458,134.8 458,186.8 458,321.9 458,076.5 Forest and woodland 163,684.3 145,711.5 105,231.8 102,759.6 95,339.7 86,404.5 Pasture, range, and other lanai 5~)8 909.8 526,323.5 481,566.3 478,927.2 471,341.4 463,098.2 Total land in farms 1,120,157.8 1,105,873.1 1,044,932.9 1,039,873.6 1,025,003.0 1,007,579.2 Irrigated Cropland Harvested 27,436.8 29,902.8 37,463.6 36,935.8 37,042.6 37,184.3 Feed crops Grainsb 5,255.4 6,585.0 10,079.8 9,799.3 9,567.3 9,516.2 RoughageC 7,483.6 9,144.~ 10,648.8 10,681.3 :11,221.8 11,072.5 Food crops Grains 2,961.9 3,785.5 4,563.8 4,488.3 4,541.D 4,490.6 Vegetables, fruits, and sugar 3,601.8 4,826.6 5,396.4 5,514.8 5,866.5 6,463.8 Othere 1,158.0 1,007.1 1,265.0 1,278.2 1,289.5 1,328.6 Other crops Oilf 395.0 479.8 1,113.5 1,090.4 1,054.1 1,090.3 Cotton, tobacco, and miscellaneous 3,465.0 4,281.2 4,789.1 4,471.9 3,892.5 3,623.8 Total irrigated crops harvestedk 24,320.7 30,110.1 37,856.3 37,324.2 37,433.4 37,585.7 Acreages are exclusive of Alaska and Hawaii. Footnotes b-f identify die 23 major crops for which acreages were projected; historical values for food, feed, and other crops include acreages of minor crops to account for total acreages of crops harvested. Includes corn, grain sorghum, oats, and barley. CIncludes hay and silage. Includes wheat, rye, and rice. Includes Irish and sweet potatoes, dry beans, and dry peas. Includes soybeans, peanuts, and flaxseed. Total crops harvested will not equal Cropland harvested because of double cropping. Cropland used only for pasture or grazing, cover, crops, legumes and soil-improvement grasses, crop failure, cultivated summer fallow, and idle land. Land occupied by houses or other buildings, lanes, roads, ditches, land in ponds, and wasteland. Includes acreages for 17 western states, Arkansas, Mississippi, Louisiana, and Florida (1960 acreage reported under 1959 for Arkansas, Mississippi. and Florida). Total irrigated crops harvested will not equal Cropland harvested because of double cropping and/or nonreporting. Bonem in 1971.3~ Preliminary projections that are subject to revision have been made to 1985 and 2000 under the Water Resources Council's 1975 National Assessment Program (Table 3.141. To test the usefulness of a simplistic national "projec- tion model," based on an extrapolation of past production growth trends and fixed water requirements per unit of output, the Series E OBERS growth rates were used with 1970 agricultural and steam-electric withdrawals data and the 1973 Census of mineral industry and manufactur- ing water-use data. Essentially the gross outputs of a 400-sector 1972 national interindustry table, updated from 1967, were aggregated to conform to the OBERS industry classification scheme. The OBERS growth rates of earnings that had been projected by sector to 2000 and 2020 in constant dollars were calculated in index terms and then applied to the 1972 gross domestic outputs by sector to project these to the target years. Water-use coefficients for the base year were calculated for the industry classifications in the form of water use in billions of gallons per day per million dollars of product output. These coefficients were then multiplied into the pro- jected levels of constant-dollar output to yield the esti- mated values of water use by sector. These values have been plotted along with the other projections in Figures 3.4 3.11. The results of the simplistic projection model compare favorably with some of the middle-range projec- tions developed by Wollman and Bonem. The values of the water coefficients used in the simplistic model for the mineral industry category may be low because of the fact that the Census data, as presented, cover only 7 percent of the total number of establishments. The 7 percent that are

Methods for Estimating and Projecting Water Demands for Water-Resources Planning 170— lln _ FIGURE 3.3 Projections to 1985 of population, food demand, food projection, and food valance in (a) the developed countries (including eastern Europe and the Soviet Union) and (b) the developing market economy countries. 196~1971=100. Data source: Reference 68. covered are nevertheless stated to represent some 98 percent of total water withdrawals. If the climatic changes that portend are in fact realized, then the irrigation demands may be substantially greater than the preliminary Water Resources Council second national assessment estimates as they are currently shown. If increased irrigation demands are to be met both in the traditionally semiarid areas of the West and in the dry farming areas of the Midwest and East, then some- thing approximating a fixed water input per unit of output may ultimately be a more realistic assumption to be made. The agricultural sector in the United States is basic to the support of the large concentrations of population in metropolitan and suburban areas. However, this sector is extremely vulnerable to any adverse climatic change that could lead to a series of crop failures. Additionally, BGD 140 I20 100 r 80~ 1 1 1 1 975 1985 2000 FIGURE 3.4 1975 Water Resources Council projections for consumptive water use. Key: , constant-water-use coefficient model; _ ; Water Resources Council preliminary projection, 1975; , Water Resources Council, 1965; Wollman and Bonem3t (high, medium, low projections). BGD, billion gallons/day. 65 12 _ 8 _ 4 _ MANUFACTURING, / STEAM- , ELECTRIC, it' _ DOMESTIC / ~ - - MINERALS _ . _ u 1 1 1 1975 1985 2000 FIGURE 3.5 1975 Water Resources Council projections for consumptive water use. Key: See Figure 3.4. household water needs are similarly vulnerable in many localities because of limited reservoir capacities. The combined conditions of drought in agricultural areas and insufficient capacity in public water supplies for met- ropolitan areas could lead to unstable political and eco- nomic conditions where populations are highly concen- trated. Unforeseen shortages of water for any protracted period of time may be difficult to contend with in terms of public health and safety. While results of the simplistic projection model of water demands constructed by the authors for the years 2000 and 2020 based on current water-use data and economic growth rates associated with a series E population growth compare favorably with the middle-range projections developed by Wollman and Bonem, both sets of forecasts, as well as others such as BGD 220 200 I80 160 140 I20 100 / / , 1 1 1 ~ 19 60 1980 2000 2020 FIGURE 3.6 Agricultural water withdrawals. Key: See Figure 3.4.

66 TABLE 3.14 Annual Water Requirements EVERARD M. LOFTING and H. CRAIG DAVIS Withdrawal Use Consumptive Use Water Requirement (mad) (mad) Categories 1975 1985 2000 1975 1985 2000 Domestic Central 21,520.4 24,698.0 29,086.0 5,003.4 5,744.8 6,756.0 Domestic Noncentral 2,072.7 2,296.0 2,371.7 1,288.5 1,392.1 1,417.5 Manufacturing Total 58,176.8 33,086.5 45,701.6 6,275.0 9,199.9 15,758.3 Food end kindred 2,500.6 1,440.3 1,137.6 310.3 465.7 770.5 Paper, pulp, and board 8,595.6 5,821.5 5,193.2 1,039.7 2,065.0 4,112.6 All other manufacturing 4,910.7 2,496.5 2,606.7 598.6 865.0 1,400.6 Textile mills 559.6 265.7 211.6 65.1 93,1 144.5 Chemicals 14,005.4 5,867.6 5,445.4 1,305.5 2,128.3 4,260.1 Primary metals 17,324.0 5,591.0 3,398.0 2,007.0 2,282.0 2,685.0 Transport, machinery 1,331.4 579.4 479.4 143.8 226.7 364.4 Petroleum refining 2,313.8 1,578.4 1,201.6 533.5 687.5 955.4 Minerals, Total 7,506.1 8,810.4 10,912.4 2,333.2 2,628.4 3,145.8 Metals 1,081.2 1,288.2 1,605.3 233.5 272.5 300.1 Nonmetals 3,518.7 4,385.7 5,745.6 470.8 599.1 785.0 Fuels 2,907.4 3,137.0 3,622.4 1,627.9 1,758.9 2,022.4 Crop Irrigation 179,053.4 184,984.5 163,652.9 92,024.5 98,153.5 93,742.2 Livestock 1,851.9 2,153.1 2,444.1 1,851.9 2,153.1 2,444.1 Steam Electric 92,602.0 86,801~0 70,047.0 2,103.0 3,647.0 9,147.0 National Parks 13.8 18.0 21.7 10.3 13.5 15.9 Fish Hatcheries 628.0 697.2 726.3 0.0 0.0 0.0 BLM Lands 1,050.7 1,129.9 1,232.8 1,050.7 1,129.9 1,232.8 National Forests 393.0 591.5 793.4 393.0 591.5 793.4 Total Requirements 364,868.8 345,266.6 326,990.0 112,333.5 124,653.5 134,453.1 Man-made Evaporation 13,114.0 13,556.2 13,779.8 13,114.0 13,556.2 13,779.8 Total Requirements plus Evaporation 377,982.7 358.822.8 340,769.8 125,447.5 138,209.7 148,232.9 Net Exports 450.7 651.7 862.2 450.7 651.7 862.2 Net Depletions 378,433.4 359,474.5 341,631.9 125,898.2 138,861.4 149,095.1 Groundwater Withdrawals 68,665.5 66,410.5 63,481.5 Net Imports 0.0 0.0 0.0

Methods for Estimating and Projecting Water Demands for Water-Reso?'rces Planning BED an 60 40 20 _ / FIGURE 3.7 Mining water withdrawals. Key: See Figure 3.4. BGD 200 _ 160 _ 120 _ 80 _ 40 _ - / / / / / _ it_ ~ 1 1 1 1 1960 1980 2000 2020 FIGURE 3.8 Manufacturing water withdrawals. Key: See Figure 3.4. 67 BGD I 000 800 600 400 t 200; 100: Rae ~ ma_ it' ~ 1960 1980 2000 2020 FIGURE 3.9 Steam-electric water withdrawals. Key: See Figure 3.4. BGD 140 120 _ 100 _ 80 _ 60 _ 40 _ 2n _ // :~< :~ 1960 1980 2000 2020 FIGURE 3.10 Municipal water withdrawals. Water Resources Council data are for domestic use only. Key: See Figure 3.4.

68 BGD 1600: 1400: 1200: 1000: 800: 600: 400: 200 _ / I I ~ 1960 1980 2000 2020 O ~ _ . . FIGURE 3.11 Total water withdrawals. Key: See Figure 3.4. those developed by the United States Water Resources Council for 1968 and 1975, may substantially understate agricultural water demands if any unfavorable climatic change is experienced during the coming 50-year plan- . . nlng perlo( .. The authors are indebted to Nathaniel Wollman and Warren Hall for helpful review comments given for an earlier draft of this chapter. BE F ERE N C E S 1. 3. .S EVERARD M. LOFTING and H. CRAIG DAVIS R. G. Thompson and H. P. Young (1973~. Forecasting water use for policy making: A review, Water Resources Res. 9,792. 2. C. T. Bowman and T. H. Mortar (1976~. Revised projections of the U.S. economy to 1980 and 1985, Mon. Labor Rev., March. R. E. Kutscher (1976~. Revised BES projections to 1980 and 1985: An overview, Mon. Labor Rev., March. 4. C. W. Howe (1972~. Economic modelling: Analysis of the interrelationships between water and society, presented at International Symposium on Mathematical Modelling Tech- niques in Water Resources Systems, Ottawa, Ont., Canada, May. . C. V. Moore and T. R. Hedges (1963~. Economics of On- Farm Irrigation Water Availability and Costs and Related Farm Adjustments, Vol. 2, California Agricultural Experi- ment Station, Giannini Foundation Research Rep. No. 263, U. of California, Berkeley. 6. R. A. Young and J. D. Bredehoeft (1972~. Digital computer simulation for solving management problems of conjunctive groundwater and surface water systems, Water Resources Res. 8, No. 3. 7. R. G. Cummings (1971). Optimum exploitation of ground- water reserves with saltwater intrusion, Water Resources Res. 7, No. 6. 8. R. G. Cummings (1971). Water resource management prob- lems in northern Mexico, unpublished paper presented at Workshop on Problems of Agricultural Development in Latin America, Caracas, Venezuela, May 17-19. 9. H. M. Stults (19661. Predicting farmer response to a falling water table: An Arizona case study, in Water Resources and Economic Development of the West, Rep. No. 15, Confer- ence Proceedings, Committee on the Economics of Water Resources Development of the Western Agricultural Eco- nomics Research Council, Las Vegas, Dec. 10. M. Gisser ( 1970~. Linear programming models for estimating the agricultural demand for imported water in the Pecos River Basin, Water Resources Res. 6, No. 4. 11. L. M. Hartman and R. L. Anderson (1962~. Estimating the value of irrigation water from farm sales data in northeastern Colorado, J. Farm Econ. 44, No. 1. 12. R. L. Anderson (1961). The irrigation water rental market: A case study, Agri. Econ. Res. 13, No. 2. 13. B. D. Gardner and H. H. Fullerton (1968~. Transfer restric- tions and the misallocation of irrigation water, Am. J. Agri. Econ. 50, No. 3. 14. E. O. Heady, H. C. Madsen, K. J. Nichol, and S. H. Hargrove (1971~. Agricultural Water Needs~uture Water and Land Use: Effects of Selected Public Agricultural and Irrigation Policies on Water Demand and Land Use, summary report prepared for the National Water Commission by the Center for Agricultural and Rural Development, Iowa State U., Nov. (available from NTIS, Springfield, Vat.. 15. J. H. Duloy and R. D. Norton (1972~. CHAC, a programming model of Mexican agriculture, draft copy of a chapter in a forthcoming book tentatively titled "Multi-Level Planning: Case Studies in Mexico" (mimeo), IBRD, Feb. Cited by C. W. Howe in Ref. 4. 16. A. Kaufman and M. Nadler (1966). Water Use in the Mineral Industry, Bureau of Mines, Information Circular 8285, U.S. Dept. of the Interior, Washington, D.C. 17. Correspondence from C. W. Grover, U.S. Water Resources Council, Washington, D.C., March 1976. 18. J. Am. Water Works Assoc., May 1957, pp. 61~741. 19. National Association of Manufacturers and U.S. Chamber of Commerce, Water in Industry, New York, pp. 45~7. 20. W. R. D. Sewell, B. T. Bower, et al. (1968~. Forecasting the Demands for Water, Policy and Planning Branch, Dept. of Energy, Mines, and Resources, Ottawa, Ont., Canada. 21. B. T. Bower ( 1966~. Economics of industrial water utiliza- tion, in Water Research, published for Resources for the Future, Inc., by The Johns Hopkins Press, Baltimore, Md., pp. 14~173. 22. C. S. Russell (1971~. Models of response to residuals man- agement actions: A case study of petroleum refining, Re- sources for the Future, Inc., cited by National Water Com- mission, Nov. 23. Water use in manufacturing, 1972 Census of Manufactures, Bureau of the Census (Sept. 1975~. 24. National Association of Manufacturers and U.S. Chamber of Commerce (1965~. Water in Industry, New York. 25. B. T. Bower (1966~. Economics of industrial water utiliza- tion, in Water Research, published for Resources for the Future, Inc., The Johns Hopkins Press, Baltimore, Md.

Methods for Estimating and Projecting Water Demands for Water-Resources Planning 26. A Report to the President by the President's Materials Policy Commission. U.S. Government Printing Office, Washington, D.C. (June 1952~. 27. National Commission on Water Quality, staff draft report, Washington, D.C. (Nov. 1975~. 28. C. R. Murray and E. B. Reeves (1972~. Estimated Use of Water in the United States in 1970, Geological Survey Cir- cular No. 676, U.S. Dept. of the Interior, Washington, D.C. 29. Data from the Federal Power Commission, Problems in Disposal of Waste from Steam-Electric Plants, 1969. (Staff study supporting the Commission's 1970 National Power Survey.) 30. L. G. Hauser and K. A. Oleson ( 1970~. Comparison of evaporative losses in various condenser cooling water sys- tems, American Conf., Chicago, Ill., April. 31. N. Wollman and G. W. Bonem (1971~. The Outlook for Water: Quality, Quantity and National Growth, published for Resources for the Future, Inc., by The Johns Hopkins Press, Baltimore, Md. 32. The Federal Power Commission's Economic Analysis Staff, cited in National Water Commission, Forecasting Water Demands (Nov. 1961), p. 154. 33. Bureau of Economic Analysis, Social and Economic Statis- tics Administration, U.S. Dept. of Commerce. 34. J. W. Wilson (1969~. The demand for electricity in the United States An empirical analysis, PhD dissertation, Cornell U., June. Cited in National Water Commission, Forecasting Water Demands (Nov. 1971), p. 157. 35. R. A. Herendeen ~ 1973~. An Energy I nput-Output Matrix for the United States, 1963: User's Guide, CAC Doc. No. 69, Center for Advanced Computation, U. of Illinois at Urbana-Champaign, Mar. 4. 36. L. G. Hauser and K. A. Oleson (1971~. Cooling water sources for power generation,J. Power Div. Am. Soc. Civil Eng. 97, POT. 37. 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