Valuing Ground Water Economic Concepts and Approaches (1997) / Chapter Skim
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6: Case Studies
6: Case Studies
Pages 127-168
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From page 127... ...
The planning and implementation of economic valuation studies requires the interdisciplinary efforts of economists, engineers, scientists, and policy-makers. These studies show that although a complete accounting for all components of the TEV of ground water is often impossible to obtain, quantifying some components can provide information to improve decision-making and increase the efficiency of the use of scarce ground water resources.
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From page 128... ...
Orange County, Use of ground water recharge in a Addresses the value of ground California coastal area to avert sea water water in storage as a deterrent to intrusion in a viable ground water sea water intrusion. basin.
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From page 129... ...
The second California example deals with the issue of irreversibilities associated with the intrusion of seawater in the ground water basin underlying Orange County, in southern California. Loss of the basin to sea water intrusion would require the Orange County Water District to rely more heavily on imported water and would preclude the use of the aquifer for water storage.
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From page 130... ...
This case study also highlights the complexities involved in conducting an empirical analysis of the value of restoring ground water resources and the impacts of uncertainties in the economic and physical dimensions, and in potential health consequences, and the public response to ground water usage. The final case study concerns the potential application of the valuation framework described in Chapter 3 and some valuation methods described in Chapter 4.
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From page 131... ...
Reduction in stream flow and wetlands will exacerbate some wildlife problems. Assessment of the Value of Ground Water The interplay of surface water use, ground water quality, and, ultimately, stream flow, creates challenges for public water resource managers as they try to
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From page 132... ...
and below-cost pricing of water in public supply projects, further complicates water management. A plan that achieved optimal use across all water resources in the basin would likely vary dramatically from the use pattern typically observed in such settings.
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From page 133... ...
It supplies most of the total public and domestic water supply and provides base flow to many of the region's exceptional surface waters. Compliance with the 1986 amendments to the federal Safe Drinking Water Act requires that all surface water used as drinking water for public water systems be filtered.
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From page 134... ...
Some parties argue that efforts to recycle runoff and sewage serve to increase or maintain ground water levels by replacing water on the ridge, in effect performing an environmental service. Others deny this claim and fear that the resorts' usage threatens water quality down slope.
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From page 135... ...
How much water is safely available from this aquifer system, and are there areas where the aquifer is potentially overdeveloped? · What is the impact of ground water withdrawals on the quality and base flow of the upland surface water systems fed by Laurel Hill Spring?
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From page 136... ...
THE BUFFER VALUE OF GROUND WATER Albuquerque, New Mexico Background The city of Albuquerque, New Mexico, like many other rapidly growing metropolitan areas in the arid Southwest, draws much of its municipal water supply from ground water. Unlike most other cities, however, Albuquerque does have rights to surface water supplies from the nearby middle Rio Grande and to waters from the Colorado River basin (San Juan and Chamba Rivers)
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From page 137... ...
and between the United States and Mexico for the scarce surface water supplies of the basin resulted in a series of compacts and agreements allocating water among the parties. Albuquerque was given rights to 48,000 acre-feet of water from the Rio Grande and 22,000 acre-feet of imported water from the Colorado River basin.
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From page 138... ...
Once city water managers understood that Albuquerque was mining ground water and not using its surface water supplies, they reexamined the long-term water management strategy. The city's failure to use its surface water supplies meant that someone else had been using those supplies.
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From page 139... ...
Eventually, mining eliminates the potential use of an aquifer as a buffer against drought. In arid regions, which are typically characterized by high annual variation in precipitation and surface water supplies, the use of ground water to meet needs during drought may be one of the most valuable ground water services.
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From page 140... ...
Continued overdrafting threatened the area's economic base. Some years earlier local growers anticipated this situation and organized the Arvin-Edison Water Storage District to bring supplemental surface water sup
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From page 141... ...
. The advent of significant surface water deliveries did not fully solve the area' s water supply problems, however.
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From page 142... ...
OCWD constructed Water Factory 21 in 1973 for the purpose of protecting the quality of the county's extensive ground water resources by preventing sea water intrusion. Loss of the basin beyond any possible use would require the district to rely on imported water for its entire water supply.
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From page 143... ...
Sea Water Intrusion in Orange County The largest body of ground water in Orange County is the coastal basin of the Santa Ana River, which yields most of the ground water produced in Orange County. The Santa Ana Gap is a coastal lowland lying between the Huntington Beach and Newport Mesas.
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From page 144... ...
Innovations to Prevent Seawater Intrusion Recharging the Basin With the importation of Colorado River water in 1940-1941 the district's water demands on the ground water basin were reduced. However, ground water levels continued to drop until 1954, when imported water was used to supplement the district's ground water replenishment program.
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From page 145... ...
The Alamitos Barrier and the Talbert Barrier have effectively halted sea water intrusion in the basin so that it can be used as a ground water storage reservoir, providing more access to available local supplies. The Value of Averting Sea Water Intrusion The principal economic effects on an area where the ground water basin is subjected to seawater intrusion are the impairment of the basin as a storage reservoir, the degradation and loss of the potable water supply stored in the basin, and the loss of the basin's value as a fresh water distribution system.
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From page 146... ...
In addition, natural runoff that percolates into a ground water basin loses economic value if it flows into a basin degraded by sea water. This fresh water supply of approximately 270,000 acre-feet per year in Orange County would become unusable as a potable source.
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From page 147... ...
Access to Orange County's valuable local ground water resource decreases the district's dependence on this more costly, less reliable imported water supply. Ground water is generally less expensive than imported water, primarily because of the development and transmission costs of the imported supplies.
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From page 148... ...
Communities in Orange County would be forced to turn to more costly imported water to meet their water supply needs if the ground water basin were lost to sea water intrusion. To replace local ground water supplies in Orange County with enough imported water from the MWD of southern California to maintain current levels of use for a 20-year period would cost water users at least $4.8 billion dollars.
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From page 149... ...
Many of the Superfund sites involve contamination of ground water resources or are listed as potential threats to local public water supply wells (Canter and Sabatini, 19941. Contaminants foundin public ground water supplies are mainly volatile organic contaminants (VOCs)
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From page 150... ...
The contaminated ground water supply was assumed to be replaced with water purchased from the Massachusetts Water Resources Authority (MWRA) , which was the least expensive alternative available to the city.
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From page 151... ...
The second management context developed in the study was more complex and was based on the underlying assumption that all the households that had previously relied on private wells as opposed to a municipal water supply system would continue to use "contaminated" water, although the extent of uses by these households could vary. The study hypothesized a range of situations from ones in which consumers avoided using the water for drinking, food preparation, and personal hygiene, in which case the direct use value of the ground water would be reflected in the costs of purchasing alternative drinking water supplies, to situations where individuals continued to consume the contaminated ground water.
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From page 152... ...
For example, in specifying the model of consumer behavior, assumptions are needed regarding the level of the potential health damages, discount rates, concentrations of TCE over time in the aquifer, and future costs of alternative drinking water supplies. These assumptions affect decisions on avoidance costs and measures of health damages and thus the direct use value attached to ground water by individuals who have private water supply wells.
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From page 153... ...
The region's ground water resources also provide a range of in situ services, such as prevention of land subsidence, reservoir functions that will buffer future drought associated with shortages in surface water supplies, bequest value, and ecological services such as maintenance of riparian habitat. Policy-makers in Arizona have struggled to reduce the extent to which ground water supplies in the region are mined.
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From page 154... ...
Tucson's Water Resources Tucson has relied on a high-quality ground water supply to meet all of its demands for water. Ground water use has exceeded natural recharge (precipitation and return flows)
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From page 155... ...
TABLE 6.2 Tucson AMA Water Demand Sector 1994 USE (in acre-feet) Percent Agricultural 97,900 31 Municipal 148,500 47 Industrial 18,600 6 Mining 45,000 14 SOURCE: Arizona Department of Water Resources, 1996.
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From page 156... ...
, 37,000 metered connections in the older parts of town were returned to ground water in October 1993. Water-quality problems were attributed to old cast iron and galvanized steel water mains and household plumbing, combined with pH and other chemical attributes of the imported surface water that encouraged corrosion.
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From page 157... ...
The "without" scenario describes the services provided in the base case and the incremental changes that result from substituting treated surface water supplies. incremental (changes in Extractive Service Flows Although Colorado River water is viewed as a high-quality water source for millions of people in the Southwest, there are several ways in which recharge using CAP water can reduce the quality of the water available for extractive uses.
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From page 158... ...
Depending on how this salt-laden wastewater is directed, the effect on ground water service flows varies. The brine stream from such plants is normally discharged into surface water or injected into deep wells.
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From page 159... ...
; and ecological services in which ground water supports surface water flows and riparian habitat. Recharge Effects If recharge is used to limit water-level declines in areas that are prone to compaction, it will help support in situ uses.
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From page 160... ...
. In the Tucson example, the difference in the extractive service flows between the two options is related primarily to the reduced pumping costs and the reduced number of wells required to serve the community, as well as the water-quality issues caused by recharge of untreated CAP water that occurs in the one option.
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From page 161... ...
Valuing Changes in In Situ Service Flows Subsidence Avoidance. The risk of subsidence is high in the central Tucson basin, where 60 percent of the city's water supply is currently pumped.
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From page 162... ...
If a direct delivery option were selected in the future, however, the buffer value of the aquifer would have been lost if most of the ground water supply in the vicinity of the wells had been removed. Methods associated with estimating buffer value, such as intertemporal optimization, may be applied (Tsur and Graham-Tomasi, 1991~.
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From page 163... ...
1991. The buffer value of ground water with stochastic surface water supplies.
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From page 164... ...
. Each study involves unique hydrogeological features, ground water quality, uses of the resource, institutional requirements and constraints, and political contexts.
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From page 165... ...
For example, in ground water valuation studies for Superfund sites, stochastic modeling of the contamination problem and potential effectiveness of cleanup measures should be used to develop ranges of resultant information that can be viewed as a type of "sensitivity analysis." Decision-makers should also consider the possible influences of uncertainties and nondelineated costs and benefits (of ground water services) as they interpret information.
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