Tables 1.4 and 1.5 encapsulate some of the major services ground water provides that give rise to economic value. (Detailed discussion of the approaches used to determine quantitative estimates of value is in Chapter 4.) Although many people already appreciate or may have intuitively accepted the nature of these services and the importance of assigning value to them, they have not engaged in widespread action to more effectively conserve, protect, and allocate these resources. Part of the problem no doubt arises from the technically demanding nature of the problem, for example, the complex behavior and properties of aquifers. In particular it is challenging to evaluate from an economic perspective the ecological services rendered by ground water since such services are not traded in markets and are viewed in a highly subjective way.
Table 1.6 (also in Chapter 4 as Table 4.5) presents an overview of the alternative valuation methods for addressing selected ground water functions/services. These economic valuation methods and existing applications are discussed in more detail in Chapter 4.
Ground water problems are receiving more attention for a number of reasons. Increased withdrawals are causing problems such as subsidence, salt water intrusion, and destruction of wildlife habitat. Public water supply systems dependent on ground water can be found in every state (Solley et al., 1993). Also, the importance of ground water as a buffer, or emergency supply, is beginning to be more widely recognized. This value was illustrated in California during the drought in the early 1990s, when demands for surface water far outstripped the available supplies. Agricultural and municipal ground water use increased dramatically, causing concerns about whether ground water protection regulations were adequate.
The importance of ground water has also changed in the context of conjunctive use. Recharge of surface water in Florida and use of effluent to replenish ground water is now common in southern California. In this context the ground water aquifer becomes an actively managed storage facility, with ground water supplies replenished by flood flows, imported surface water, and treated effluent. Water is cycled through the aquifer materials on a relatively short term basis and provides a buffer against shortages of surface water.
The environmental values associated with ground water are also becoming more widely recognized. Just as the ecosystem concept is gaining more recognition in habitat management to protect animal species, the role of ground water in the support of surface water supplies, wetlands, and riparian habitat is more clearly understood.
Most decisions regarding ground water development, use, or protection are