New Strategies for America's Watersheds (1999) / Chapter Skim
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3 Regional Variations
3 Regional Variations
Pages 56-111
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From page 56... ...
The physical hydrology includes precipitation, evaporation, the amount of water held in the soil, streamflow, groundwater, and water quality. Precipitation The contiguous United States receives an average of approximately 75 centimeters (30 inches)
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From page 58... ...
Evaporation Evaporation is important to water supply and watershed management because it represents the natural loss of otherwise available water. One measure of the concept is the combination of potential evaporation and transpiration, known as potential evapotranspiration or PET.
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From page 59... ...
15 10 5 O 25 20 15 10 O 5 10 6 J A Seallle J A J O New Odeans i10 5 O 20 15 O Record 15- high ~38.10 ELI it' A J O / Months Record Low -ill _ _ # _ A J Albuquerque J A J O Boston - 25.40 e # -12.70 o FIGURE 3.2 mostly preciphaUon: means Ed extremes.
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From page 61... ...
Regional Variations ._ A=_ .t 1 t~ ' few _.
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From page 62... ...
62 ~~ ~o He omit )
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From page 63... ...
as well as year-to-year variation. One important consideration in watershed management is what proportion of the year's moisture loss occurs during the growing season (May to October)
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From page 65... ...
The runoff rates are roughly predicted by the soil water budgets.
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From page 67... ...
, there is greater river flow in the eastern half of the country and in the Northwest than elsewhere (Figure 3.11~. One of the most important considerations in watershed management is dealing with floods.
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From page 71... ...
The elimination of lead in gasoline has caused a dramatic decline in atmospheric delivery, and surface waters now contain almost immeasurably low amounts, especially in bioavailable dissolved foes (Windom et al., 1991; Benoit, 1994~. Changes in forest ecosystems can also change water quality.
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From page 72... ...
While the regional flow of water in aquifers generally reflects the general surface topography above, ground water resources in one watershed may also be fed by surface
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From page 73... ...
73 ran & ~ `l' ~ V: o sit .?
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From page 74... ...
74 ~ ~ fir - ~ ~ - ~, ~ ~ ;jP" ~7'° S -- - ~ ~_ .
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From page 75... ...
To date, management has generally underemphasized ground water problems and responses as a component of water resource conservation and rehabilitation (GAO, 1991~. Indeed, watershed management too often focuses only on surface waters, or if ground water resources are recognized only volume and accessibility receive notice whereas quality and biologic characteristics are also important.
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From page 76... ...
If ground waters are connected components of river, lake, and marine ecosystems, vital ecosystem linkages may have been disconnected by ground water abstraction and pollution. Watershed management must consider subsurface water resources and influences of land-use activities, especially ground water abstraction and subsurface injection of waste water and other pollutants, on these resources.
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From page 77... ...
Changes in forest ecosystems can also change water quality. For instance, gypsy moth defoliation of forested uplands in Virginia led to dramatic increases in concentrations of nitrates in stream waters.
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From page 79... ...
3-29 Sin.
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From page 80... ...
Land use and land cover, which influence water quality, also tend to have regional patterns. Many of these represent human-induced perturbations (e.g., agriculture and urbanization)
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From page 81... ...
Such regional variation imposes inherent limits on attainable water quality, biotic assemblages, and trophic states that should be considered in watershed management. For example, stream-water quality in 107 watersheds across Ohio varied substantially among five ecological regions, even though all were minimally disturbed by human activity (Larsen et al., 1988~.
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From page 82... ...
These efforts reflect the strong push toward coordinated ecosystem management called for by an Interagency Ecosystem Management Task Force formed by the White House Office on Environmental Policy in 1993. The Task Force was asked to find ways to implement an ecosystem approach to environmental man
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From page 85... ...
Agricultural land use and on-site residential waste disposal pose water quality concerns. Thus while watershed management is needed across the entire landscape, specific watershed management problems vary depending on the type of land use and the pattern of population settlement within a given area.
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From page 86... ...
86 it: .'
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From page 88... ...
First, they alter the land surface of watersheds, affecting both quantity and quality of streamflow and lakes. Second, streams and streamflow are directly affected by channel and floodplain alterations, dams, and water transfers, while water quality is affected by point sources.
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From page 89... ...
89 :~ .~ I o row
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From page 90... ...
For many years, the official policy of the U.S. Forest Service and other governmental agencies was to suppress fires.
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From page 91... ...
Particulate matter concentrations from air pollution and street abrasion may approach levels from TABLE 3.1 Comparison of Stormwater Quality from Various Sources for Selected Parameters Study Location Total BOD solids (mg/l)
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From page 92... ...
Levels of some pollutants in urban runoff are worse than raw domestic sewage (Table 3.2~. Roads, including highways, are often rural extensions of the urban phenomena, and can affect outlying areas.
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From page 93... ...
, herbicides, and pesticides. The movement of these chemicals into streams is enhanced because they often adsorb onto soil particles, and soil erosion is usually greatest from cropland.
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From page 94... ...
Such poorly managed pasture produces more overland flow, which causes soil erosion and allows animal wastes to be washed into streams. Because of sparse vegetation and poorly developed soil, semi-arid rangeland is even more fragile than pasture, and has been heavily abused and eroded in the past (Cooke and Reeves, 1976; Branson et al., 1981~.
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From page 95... ...
(Figure 3.22~. The management of migrating sediment can be an important aspect of watershed management (Trimble, 1993~.
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From page 97... ...
FIGURE 3.22 Severe erosion and sedimentation from poor agricultural land use in the Southern Piedmont, 1700-1970. Note the aggradation of streams, the transformation of floodplain into swamps, and the transfer of sediment downstream and its relation to land use.
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From page 98... ...
Ditching these mainstream channels lowers the base level of tributaries, thus destabilizing them and causing channel erosion which helped fill the trunk channel (Happ et al., 1940~. Such complications make management of such channels a growing art (Shields et al., 1995; Wang et al., 1997~.
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From page 99... ...
In addition much of the sediment is usually deposited at the head of the reservoir, creating a rise in base level that sometimes causes the river to aggrade for several miles upstream. Furthermore, while the trapping of sediment by a reservoir may improve downstream water quality, the sediment-starved water may degrade channels for many miles downstream (Williams and Wolman, 1984~.
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From page 100... ...
Stratification of deep reservoirs can also cause undesirable changes in water quality, such as when bottom water isolated from the atmosphere suffers oxygen depletion. Whether caused by dams, water transfer, or land use alteration, changes of stream flow regimes can have significant effects on aquatic and terrestrial ecosystems.
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From page 101... ...
This concentrate salt and other minerals at the surface, often damaging the soil and polluting local ground water. Point Sources of Pollution Unlike the nonpoint sources considered earlier in this section, point sources of water pollution are released, often deliberately, into a stream at an identifiable place.
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From page 104... ...
Increasingly stringent public health codes and inspections are reducing the ground water and surface water pollution caused by these systems. However, in many places, septic systems are still placed too close to the ground water table, leading to ground water pollution, or in soils that are too thin, allowing the effluent to move along bedrock into springs and streams.
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From page 105... ...
(ed.) Water Resources Handbook.
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From page 106... ...
(ed.) Water Resources Handbook.
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From page 107... ...
1987. Analysis of regional patterns in lake water quality: Using ecoregions for lake management in Minnesota.
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From page 108... ...
1988. A regional approach to assess attainable water quality: an Ohio case study.
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From page 109... ...
1995. Urban stormwater quality: summary of contaminant data.
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From page 110... ...
(ed.) Water Resources Handbook.
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From page 111... ...
1997. Release of NO3- to Surface Waters Following Forest Defoliation by the Gypsy Moth.
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