Valuing Ground Water Economic Concepts and Approaches (1997) / Chapter Skim
Currently Skimming:
2: Ground Water Resources: Hydrology, Ecology, and Economics
2: Ground Water Resources: Hydrology, Ecology, and Economics
Pages 31-46
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 31... ...
Ground water quality and the costs of extraction depend on the geologic and hydrologic characteristics of a given aquifer as well as the economic circumstances that characterize the particular uses to which ground water is devoted. Both the current and future values of ground water, then, are determined jointly by the interaction of geologic/hydrologic factors and economic factors.
|
From page 32... ...
Evaporation and transpiration, along with stream flows, are the principal pathways by which it leaves. Runoff, which is overland flow, can be augmented by interflow, which operates below the surface but above the water table, and by base flow, which refers to the discharge to streams from the saturated portion of the system.
|
From page 33... ...
Since unconfined aquifers tend to be found uppermost in a ground water system, they are frequently called surficial aquifers. Unconfined aquifers are the first to receive water infiltrating from the surface.
|
From page 34... ...
- - -.-.-.-.-.- - -.- -.-.-.-. FIGURE 2.2 Unconfined aquifer and its water table; confined aquifer and its potentio metric surface.
|
From page 35... ...
This means that water tables in unconfined aquifers and the potentiometric surfaces in confined aquifers remain stable. When this steady state is disturbed by ground water pumping or diversion of customary sources of recharge, water tables and potentiometric surfaces respond accordingly.
|
From page 36... ...
Indeed, where available, ground water basins afford benefits of storage, conveyance, and treatment that often render the ground water resource preferable to surface water alternatives from the standpoint of health protection, technical simplicity, economy, and public acceptance.
|
From page 37... ...
Incentives to conserve voluntarily are absent, since water not pumped is available to competing users and will not necessarily be conserved for future periods. Thus, competitive pumpers often ignore user costs both because they believe that self-discipline will not effectively conserve supplies for the future and because they believe that the impact of their own pumping on the water table will be small.
|
From page 38... ...
Moreover, in assessing the economic desirability of overdraft, we must account for certain adverse impacts, such as land subsidence, salt water intrusion, and deleterious effects on surface water and aquatic habitats The geological substrate of aquifers differs from location to location, with materials ranging from coarse sediments to fractured rock. Substrates that consist of fine "rained sediments such as clays tend to compact when water is removed, resulting in elimination of the pore spaces that previously contained water.
|
From page 39... ...
A number of methods are available to combat salt water intrusions, including artificial recharge, reductions in extractions, establishment of a pumping trough along the coast, formation of pressure ridges through artificial water injection, and installation of subsurface barriers. Discharges from unconfined aquifers are the source of about 30 percent of the nation's stream flow (Frederick, 1995~.
|
From page 40... ...
High water tables may also support riparian species in areas where surface flows are ephemeral. The ecological services of ground water are particularly dramatic in cases where ground water supports habitat for endangered species.
|
From page 41... ...
Surface water is generally contaminated rather quickly and has the ability to purge the contaminant in a short period of time. Both natural and artificial cleanup of ground water are lengthy processes because of slower flow rates, slower dilution, and reduced capacity for reoxygenation.
|
From page 42... ...
Injection wells Land application Category IV Sources discharging as consequence of other planned activities Irrigation practice Pesticide application Fertilizer applications Animal feeding operations De-icing salt applications Urban runoff Percolation of atmospheric pollutants Mining and mine drainage Sources designed to store, treat, and/or dispose of substances; discharged through unplanned release Landfills Open dumps Surface impoundments Waste tailings Waste piles Materials stockpiles Aboveground storage tanks Underground storage tanks Radioactive disposal sites Category V Sources providing conduit or inducing discharge through altered flow patterns Production wells Other wells (nonwaste) Construction excavation Sources designed to retain substances during transport or transmission Pipelines Material transport and transfer Category VI Naturally occurring sources whose discharge is created and/or exacerbated by human activity Ground water-surface water interactions Natural leaching Salt water intrusion, brackish water SOURCE: Office of Technology Assessment, 1984.
|
From page 44... ...
In the face of these newly perceived difficulties, the task of restoring ground water quality seems considerably more daunting than when the Resource Conservation and Recovery Act (RCRA) and Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)
|
From page 45... ...
Ground water supports microbial habitats in the subsurface and surface flows that sustain riparian habitats. Connections between ground and surface waters are better defined in theory than in application.
|
From page 46... ...
· Ground water management entities should consider appropriate policies such as pump taxes or quotas to ensure that cost of using the water now rather than later is accurately accounted for by competing pumpers. · Because ground water resources are Unite, decision-makers should take a long-term view in all decisions regarding valuation and use of the resources.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.