In analyses used to develop Bulletin 160-93, a normalized 1990 was used as the base year. (Normalization is the process of adjusting actual water use or supply in a given year to account for unusual events such as dry weather conditions, government interventions for agriculture, rationing programs, or other irregularities.) In 1990, California generally had adequately reliable supplies that met average annual urban, agricultural, and environmental water demands. However, the 1987-92 drought caused shortages in some California communities, such as Santa Barbara County, and impacted environmental resources, such as Central Valley wetland habitat.
Prior California Water Plan updates determined the existing base case for water supply and demand then balanced forecasted future demand against existing supply and against future supply and demand management options. To better illustrate overall supply availability, Bulletin 160-93 presents two water supply and demand scenarios, an average year and a drought year, for the 1990 level of development and for forecasts to 2020. What follows is an overview of California's surface and ground water supplies and of water quality problems that affect the availability of supply. At the close of each section are Bulletin 160-93 recommendations for improving water management planning and addressing water quality issues. Figure ES-3 shows the disposition of California's average annual total water supply.
The Sacramento and San Joaquin rivers have provided an average of nearly 15.5 million acre-feet annually for urban and agricultural uses. The supply for these uses could decrease by roughly 1 to 3 maf because of potential operational and institutional changes discussed in Chapter 1.
As Arizona and Nevada continue to use more of their allocated Colorado River supplies, imports to the South Coast Region for urban and agricultural uses could eventually decline from about 5.2 to 4.4 maf annually, which is California's allocated Colorado River supply. (See Figure ES-4 for locations of major water project facilities in California.) In past years, Arizona and Nevada had been using less than their share of Colorado River water, and their unused supply was made available to California. Southern California was spared from severe rationing during most of the 1987-92 drought primarily because of the 600,000 af annually of unused Colorado River water made available to the Metropolitan Water District of Southern California. Even with this supply, however, much of Southern California experienced significant rationing in 1991. Supplemental Colorado River water cannot be counted on to meet needs in the future as Arizona and Nevada continue to use more of their Colorado River allocations.
The 1987-92 drought induced many creative approaches for coping with water shortages throughout California, including construction of more interconnections between local, State, and federal water delivery facilities. The City of San Francisco's connection to the State Water Project's South Bay Aqueduct allowed emergency drought supplies to be conveyed into the city's system. Toward the end of the drought, the City of Santa Barbara constructed a sea water desalting facility and received limited SWP supplies through an emergency interconnection and a series of exchanges with other water agencies. Throughout California, water agencies were buying and exchanging water to meet critical needs. The State Drought Water Bank played a vital role in meeting some of those critical needs.
Prior to changes in water allocations from the Sacramento-San Joaquin and Colorado river systems, California had roughly enough water to meet average annual urban and agricultural water demands at the 1990 level while complying with existing SWRCB standards, as specified in D-1485. Table ES-1 shows California's water supply with existing facilities and programs as operated in accordance with D-1485.
Average annual supplies at the 1990 level of development are about 63.5 maf (includes natural flows dedicated for instream use and ground water overdraft) and could decrease to 63 maf by 2020 without any additional facilities or programs. A possible 800,000-af reduction in Colorado River supplies could be offset by short-term transfers and increased SWP Delta diversions, in addition to water management programs of the MWDSC. The 1990 level drought year supplies are about 50.4 maf and could decrease about 1 maf by 2020 without additional storage and water management options. However, until solutions to complex Delta problems are identified and implemented, Delta diversions will continue to be impaired.
Annual reductions in total water supply for urban and agricultural uses could be in the range of 500,000 af to 1 maf in average years and 2 to 3 maf in drought years. These reductions result mainly from compliance with the ESA biological opinions and proposed EPA Bay-Delta standards. Until a Delta solution that meets the needs of urban, agricultural, and environmental interests is identified and implemented, there likely will be water supply shortages in both dry and average years.
Bulletin 160-93 analyses found that baseline hydrologic and water development data used in preparing statewide supply and demand balances need to be updated. The last major inventory of such conditions was Bulletin 1, Water Resources of California, published in 1951. Bulletin 160-93 thus recommends that DWR should initiate work to update and maintain this resource document to incorporate more recent hydrologic data, including 40 more years of runoff data.
California's ground water storage in some 450 ground water basins statewide is about 850 maf, roughly 100 times the State's annual net ground water use. Probably less than half of the ground water is usable because of quality considerations and the cost of extraction. However, the large quantity of good quality ground water in storage makes it a crucial component of California's total water supply. Ground water played a vital role in helping the State through the 1987-92 drought.
In a year of average precipitation and runoff, an estimated 15 maf of ground water is extracted and applied for agricultural, municipal, and industrial use. There is a substantial amount of ground water recharge from surface water and ground water used to irrigate agricultural crops. Some of the irrigation water flowing in unlined ditches and some of the water that is applied to irrigate crops infiltrates into the soil, percolates through the root zone and recharges the ground water basins (see Figure ES-5).
The annual net use of ground water is ground water extraction minus deep percolation of applied water. The 1990 statewide average annual net ground water use was about 8.4 maf. The use of prime supply from ground water basins for 1990 was about 7.1 maf, and the remaining 1.3 maf was overdrafted from the basins. (Ground water prime supply is the long-term average annual percolation into major ground water basins from precipitation and from flows in rivers and streams.) Table ES-2 shows 1990 level use of ground water and overdraft by hydrologic region. The amounts shown include an estimated 200,000 af of overdraft resulting from possible degradation of ground water quality in adjacent basins located in the trough of the San Joaquin Valley. Poor quality ground water moves eastward, displacing good quality ground water in the trough of the valley. The concentration of total dissolved solids in the valley 's west side ground water generally ranges from 2,000 to 7,000 milligrams per liter: TDS in the valley's east side basin ranges from 300 to 700 milligrams per liter.
Annual ground water overdraft has diminished to about two-thirds of what it was in 1980 (when ground water overdraft was last studied), from roughly 2 maf in 1980 to about 1.3 maf in 1990. This reduction has mainly occurred in the San Joaquin Valley and is due to the benefits of imported supplies to the San Joaquin River and Tulare Lake regions; construction and operation of new reservoirs in the San Joaquin River Region during the 1960s and 1970s; and prudent surface and ground water management, including conjunctive use of these supplies. However, until key Delta issues are resolved and additional water management programs are implemented, the reductions in overdraft seen in the San Joaquin Valley during the last decade will reverse as more ground water is pumped to make up for lost surface water supplies, some of which formerly came from the Delta. In the long-term, continued overdraft is not sustainable. As such, overdraft is not included as a future supply.
Conjunctive use operations, which helped reduce ground water overdraft, will continue to be refined and made more effective in the future. Efficient use of surface and ground water through conjunctive use programs has become an extremely important water management tool. Such programs are generally less costly and cause fewer adverse environmental impacts than traditional surface water projects because they increase the efficiency of existing supply systems without requiring major facility additions. However, conjunctive use programs must address potentially undesirable results such as loss of native vegetation and wetland habitat, adverse effects on third parties and fish and wildlife, land subsidence, and degradation of water quality in the aquifer.
Bulletin 160-93 recommends that the State encourage efforts to develop ground water management programs at the local and regional levels and to remove legal, institutional, financial, and other barriers that limit conjunctive use of ground water basins. The programs should be focused on solutions to clearly identified problems, such as overdraft, and natural and human-caused contamination so as to optimize the use of surface and ground water resources. Specific recommendations are as follows:
Water quality directly affects the quantities of water available for use in California. Poor water quality has inherent costs, such as treatment and storage costs for drinking water, reduced crop yields, higher handling costs, and damage to fish and wildlife. Avoiding these costs by protecting water sources from degradation in the first place is one of California's more pressing water management problems.
Of critical importance to many Californians is the water quality of the Sacramento-San Joaquin Delta. Water soluble minerals, municipal and industrial waste discharges, and agricultural drainage increase the salt content of water as it flows from higher elevations to the Delta. Sea water intrusion is a major source of salts in Delta water supplies. Bromides from sea water are of particular concern because in combination with dissolved organic compounds present in soil, bromides contribute to the formation of harmful disinfection byproducts during water treatment processes. On average, Delta influences are responsible for elevating the salt concentration at Banks Pumping Plant to about 150 milligrams per liter above that of the fresh water inflows to the Delta. Most of the Delta water quality objectives relate to salinity. The SWP and CVP are required to release sufficient fresh water to meet Delta salinity standards.
Numerous aspects of water quality can affect fish and wildlife habitat and result in monetary or environmental costs. An example is selenium in agricultural drainage from the San Joaquin Valley which was used to supply wetland habitat in the valley. In this case, elevated selenium concentrations caused severe reproductive damage to fish and wildlife species, particularly to birds using the wetlands.
Human activities introduce a variety of pollutants that contribute to degradation of water quality. Mining can be a major source of acids and toxic metals. Agricultural drainage may contain chemical residues, toxic elements, salts, nutrients, and elevated concentrations of chemicals that cause harmful disinfection byproducts. Municipal and industrial discharges, including storm runoff, are regulated by State and federal environmental protection laws and policies. Waste water must be treated to render it free of certain disease-carrying organisms and reduce its environmental impact. Unfortunately, normal waste water treatment plant processes may not completely remove all water-borne synthetic chemicals. Increasingly, more stringent and costly water quality standards for public health are affecting the continued reliability and costs of water supplies.
Disease-causing organisms and other harmful microorganisms found in untreated water can pose serious health risks. Federal and State drinking water standards have been adopted to protect the health of consumers. The California Department of Health Services, Office of Drinking Water, promulgates and enforces State standards and enforces federal standards. Most drinking water quality standards are met by California's municipal drinking water utilities. However, some drinking water regulatory activities may conflict. For example, concern over surviving pathogens spurred a rule requiring more rigorous disinfection. At the same time, there is considerable regulatory concern over trihalomethanes and other disinfection byproducts, resulting from disinfection of drinking water with chlorine. The problem is that if disinfection is made more rigorous, disinfection byproduct formation is increased. Additionally, poorer quality source waters with elevated concentrations of organic precursors and bromides further complicate the problem of reliably meeting standards for disinfection while meeting standards for disinfection byproducts.
New and more costly federal and State surface water treatment rules (effective in June 1993) require that all surface water supplied for drinking receive filtration, high level disinfection, or both. The cost of constructing new filtration facilities to meet new regulations can be quite high. The U.S. Environmental Protection Agency estimates the annual nationwide cost of treating drinking water to meet existing and new standards will be $36 million a year in the early 1990s, $539 million annually by 1994, and will rise to $830 million, as a result of the need to make long-term capital investments, before stabilizing at $500 million a year by the year 2000. These estimates demonstrate that major costs will result from meeting the new standards. The regulatory community will have to carefully balance the benefits and risks associated with pursuing the goals of efficient disinfection and reduced disinfection byproducts. One essential corollary action will be to make any source water quality improvements that are feasible.
There are many water quality problems which can result in cost, either direct or environmental. In turn, these impacts reduce flexibility in water supply planning and management. California's record has been a good one, for an industrialized state. Most of our waters remain fit for fish and wildlife, and for multiple uses by people. However, the rapidly growing population and continued industrialization will continue to greatly challenge our ability to maintain and improve water quality. If we are to meet this challenge successfully, it will require the best efforts of government, industry, and, most of all, concerned citizens. Bulletin 160-93 put forth the following recommendations about solving water quality problems: