Glossary of Water Use Terms Acre-foot-A volume of water covering an acre of land to a depth of 1 foot, or 325,851 gallons. Consumptive use-Amount of water lost to the immediate water environment through evaporation, plant transpiration, incorporation in products or crops, or consumption by humans and livestock. Ground water-Generally all subsurface water as opposed to surface water. Specifically, water from the saturated subsurface zone (zone where all spaces between soil or rock particles are filled with water). Industrial withdrawals/use (other than thermoelectric)-Includes the water withdrawn/consumptively used in facilities that manufacture products (including use for processing, washing, and cooling) and in mining (including use for dewatering and milling). Irrigation withdrawals/use-Includes the water withdrawn/consumptively used in artificially applying water to farm. and horticultural crops. Some data sources include water to irrigate recreational areas such as parks and golf courses. Loss-Water that is lost to the supply, at the point of measurement, from a nonproductive use, including evaporation from surface-water bodies and nonrecoverable deep percolation. Overdrafting-Withdrawing ground water at a rate greater than aquifer recharge, resulting in lowering of groundwater levels. Also referred to as aquifer mining. Public and rural domestic withdrawals/use—Includes the water withdrawn/consumptively used by public and private water suppliers and by self-supplied domestic water users. Recharge-The percolation of water from the surface into a groundwater aquifer. The water source can be precipitation, surface water, or irrigation. Return flow-Water that reaches a surface-water source after release from the point of use, and thus becomes available for use again. Surface water-An open body of water such as a stream, river, or lake. Thermoelectric withdrawals/use-Includes the water withdrawn/consumptively used in the generation of electric power with fossil-fuel, nuclear, or geothermal energy. Irrigation water application-The depth of water applied to the field. Irrigation application quantities differ from irrigation withdrawals by the quantity of conveyance losses. Withdrawal-Amount of water diverted from a surface-water source or extracted from a groundwater source. Instream Water Flows Increased demand for instream water flows have intensified competition for limited water supplies in many areas. Water historically withdrawn for consumptive use in irrigation and municipal sectors, or impounded for navigation and hydropower generation, is finding a new “use” as instream flows for recreational and environmental purposes. Instream flow requirements are increasingly guaranteed through legislatively mandated transfers, and in some cases, direct market purchases. Recreation. Demand for water-based recreation has generally increased over time with expanding populations, leisure time, and disposable income. While water demanded for recreation is difficult to quantify due to the multi-use nature of recreational waters, the increase in participation provides an indicator of the increased demand for water-based recreation activities. The number of adults participating in boating activities nationally-including sailing, motor boating, water skiing, and canoeing-has expanded from 49.5 to 60.1 million (21 percent) since 1982 (Forest Service and others, 1995). Swimming in natural water bodies has increased from 56.5 to 78.1 million persons (38 percent) over the same period. Fishing activity has declined 3 percent, from 60.1 to 58.3 million persons. Wildlife habitat. Wildlife, including but not limited to endangered species, often competes with out-of-stream uses for water resources. Many wildlife communities and their habitats-aquatic, riparian, wetland, and estuarine-depend on water. Efforts to protect wildlife and habitat may involve restrictions on water withdrawals, timing of deliveries, lake storage levels, and drainage flows. Instream flow restrictions to protect wildlife habitat has important implications for irrigated production and farm income. The responsibility of private water developments located on public lands to provide water for downstream fish and wildlife habitat is being "reexamined" through Section 389 of the 1996 Farm Act, which requires a Water Rights Task Force. The task force will study the issue of water rights for environmental protection on national forest land, the protection of minimum instream flows, and the protection of water rights that involve facilities on Forest Service lands. Endangered species. Aquatic plant and animal species, and other predatory species that depend on healthy aquatic systems, may be highly sensitive to changes in instream water conditions. There are currently 663 species nationwide listed as "threatened" or "endangered" under the Federal Endangered Species Act (ESA). Current species listings specify various water flow-related reasons for species decline, potentially related to irrigation. These include water diversion/drawdown (141 species), water-level fluctuation (82 species), water-level stabilization (26 species), water temperature alteration (61 species), reservoirs (103 species), groundwater drawdown (71 species), and salinity alteration (14 species) (computed from data supplied by Biodata Inc., Golden, CO, 1995). The restoration of aquatic and riverine ecosystems to protect and recover endangered species has emerged as one of the most critical agricultural water-supply issues of the 1990's. Many of the current conflicts involve allocation of surfacewater flows in western river systems. This reflects various factors particular to the West-the unique biota of many western river systems; the scarcity of renewable water supplies in an arid environment; and the nature of water demands based on the concentration of irrigated production and rapid urban growth. However, conflicts involving wildlife and agriculture are not limited to surface water, and are no longer limited to the arid Western States. Examples of instream flow competition. In the Pacific Northwest, a major Federal/State effort is underway to restore declining native salmon stocks of the Columbia-Snake River Basin, including three stocks listed under the ESA. Hydropower generation, irrigation diversions, land-use activities (logging, mining, and grazing), and fish harvesting have all contributed to the decline through extensive loss and degradation of salmon habitat. Increasing instream flow velocities to assist migrating salmon-through reservoir drawdown along the lower Snake River (Washington/Oregon) and reduced irrigation diversions in the upper Snake River (Idaho/Oregon)-represents a major element of recovery strategies under consideration (Aillery and others, 1996). In California's San Francisco Bay/San Joaquin-Sacramento River Delta (Bay/Delta) area, efforts are underway to manage flows to restore endangered fish species and federally protected migratory waterfowl. The Bay/Delta region is important, both as a pumping/transfer point for agricultural and urban water supplies for much of central and southern California and as a natural site of ecological significance. Increased freshwater outflows from the Bay/Delta, linked to salinity standards, are being used to improve estuarine habitat. The higher water outflows translate into reduced water supplies for agriculture. Additionally, adjustments in river management to improve species protection are limiting the timing of withdrawals for agricultural purposes. Progress on solutions is being made through Federal, State and local cooperation (McClurg, 1996). --cont. on next page Instream Water Flows (cont.) The Edwards Aquifer region of south-central Texas illustrates the interaction between ground water and species protection. Extensive groundwater pumping for agricultural and urban uses contributes to annual declines in the aquifer water level, which reduces flows from aquifer-fed springs that support habitat for endangered aquatic species. The situation is compounded by the nature of the aquifer, which has high recharge from precipitation, and is therefore susceptible to the vagaries of weather and drought. Potential restrictions on groundwater use in the region to ensure minimum spring flows would impact irrigated agriculture (Baldwin and others, 1993 and Collinge and others, 1993). In South Florida, extensive water-control infrastructure and management has severely altered the natural hydrologic cycle, contributing to the declining productivity of the natural ecosystem (Finkl, 1995). Wetland conversion for agricultural and urban uses has substantially reduced available wetlands for wildlife habitat and other environmental uses. Of the remaining wetlands, large areas are seriously degraded due to disruptions in the quantity, timing, and distribution of flows to meet water-supply and flood-control purposes. In addition, land-use activities have contributed to impaired water quality in some areas. A major effort is underway at the Federal and State level to restore natural hydrologic functions, to the extent practicable, while meeting water-supply and flood-control objectives for agriculture and an expanding urban sector (SFWMD, 1995). . (1994). 1992 Census of Agriculture. Volume 1, Parts 1-51. U.S. Government Printing Office, Washington, DC. (1990). Farm and Ranch Irrigation Survey (1988). Volume 3, Part 1 Related Surveys of 1987 Census of Agriculture, AC87-RS-1. U.S. Government Printing Office, Washington, DC. (1989). 1987 Census of Agriculture. Volume 1, Parts 1-51. U.S. Government Printing Office, Washington, DC. (1986). 1984 Farm and Ranch Irrigation Survey. Special Report Series, AG84-SR-1. U.S. Government Printing Office, Washington, DC. (1984). 1982 Census of Agriculture. Volume 1, Parts 1-51. U.S. Government Printing Office, Washington, DC. . (1982). 1979 Farm and Ranch Irrigation Survey. Volume 5, Part 8 Special Reports of 1978 Census of Agriculture, AC78-SR-8. U.S. Government Printing Office, Washington, DC. U.S. Department of the Interior, Bureau of Reclamation (no date). 1995 Irrigation Water Rates, Central Valley California. Bureau of Reclamation; Mid-Pacific Region, Sacramento, CA. (no date). 1991 Summary Statistics. Bureau of Reclamation; Analysis, Contracts, and Lands Division; Denver, CO. U.S. General Accounting Office (1996). "Bureau of Reclama- Recent ERS Research on Water Issues Irrigation Water Use, 1994, AREI Update, 1996, No. 8 (Noel Gollehon and Marcel Aillery). This update presents Statelevel information on water sources (onfarm wells, onfarm surface, and off-farm surface) and irrigated acres by crop based on the 1994 Farm and Ranch Irrigation Survey. Water Supplies, AREI Update, 1996, No. 3 (Noel Gollehon and Marcel Aillery). This look at the 1996 spring water supply forecasts and conditions highlights the drought area in the Southwest and Southern Plains, near- to above-normal irrigation supplies in the West, and adequate subsoil moisture conditions in the East. Salmon Recovery in the Pacific Northwest: Agricultural and Other Economic Effects, AER-727, Feb. 1996 (Marcel Aillery, Paul Bertels, Joseph Cooper, Michael Moore, Steve Vogel, and Marca Weinberg). The agricultural effects of two proposed Snake River management measures-reservoir drawdown on the lower Snake and reductions in irrigation water supplies in the upper Snake-considered to recover three salmon runs are analyzed. For the Northwest region, adjustments in crop production could lower producer profit by $4-$35 million annually (less than 3 percent of the 1987 baseline), depending on specific alternatives. Economic Analysis of Selected Water Policy Options for the Pacific Northwest, AER-720, June 1995 (Glenn Schaible, Noel Gollehon, Mark Kramer, Marcel Aillery, and Michael Moore). Irrigated agriculture in the Pacific Northwest could use significantly less water with minimal impact on agricultural economic returns. Net water savings for field crops of up to 18 percent of current use levels could be realized with less than a 2-percent decline in economic returns. Combining different approaches spreads the conservation burden among farmers, water suppliers, and production regions. "Multicrop Production Decisions in Western Irrigated Agriculture: The Role of Water Price," American Journal of Agricultural Economics, 76:859-874, Nov. 1994 (Michael Moore, Noel Gollehon, and Marc Carey). Econometric estimates of water demand and irrigated crop supply functions for four regions of the West provide the statistical base for this analysis. The analysis examined irrigator response to shortrun water price change, measured as increases in groundwater pumping cost. Findings suggest that irrigators respond primarily at the extensive margin-changing the acres devoted to specific crops-rather than at the intensive margin-changing the quantity of water applied during the irrigation season. "Alternative Models of Input Allocation in Multicrop Systems: Irrigation Water in the Central Plains," Agricultural Economics, 11:143-158, Dec. 1994 (Michael Moore, Noel Gollehon, and Marc Carey). This analysis compared different farm-level models of irrigation decisionmaking on farms with multiple crops in the Central Plains region. Water was modeled three ways: as a variable input, an input used without regard for price, and a fixed-allocatable input. The model considering water a fixed-allocatable input dominated the other models in both model specification tests and prediction accuracy measures. (Contact to receive reports: Noel Gollehon, (202) 219-0413 [gollehon@econ.ag.gov]) 2.2 Water Quality WATER Agricultural production often emits pollutants that affect Producing food and fiber involves many activities and practices that can affect the quality of water resources under and near the field. For example, tilling the soil and leaving it without plant cover for extended periods of time results in accelerated soil erosion. The use of chemical inputs increases the probability that some of these materials will wash off or leach through the field to enter water resources. Irrigation can move salt and other dissolved minerals to surface water. Livestock operations produce large amounts of waste which, if not properly disposed of, can threaten human health as well as contribute to excess nutrient problems in streams, rivers, and lakes. Quality of the Nation's Water The Clean Water Act (passed in 1972 as the Federal .... 93 dissolved oxygen. Biological criteria describe the expected attainable community attributes and establish values based on measures such as species richness, presence or absence of indicator taxa, and distribution of classes of organisms (EPA, 1994). Narrative water quality criteria define conditions and attainable goals that must be maintained to support a designated use. Narrative biological criteria describe aquatic community characteristics expected to occur within a water body. Surface-Water Quality The Nation's surface-water quality has improved since 1972, primarily through reductions in pollution from point sources. However, many water quality problems remain. Water Quality Inventories, published by the U.S. Environmental Protection Agency (EPA), show no major improvement in the quality of the Nation's rivers, lakes, ponds, and estuaries since 1990 (EPA, 1995). Agriculture is cited by States as a leading source of water quality impairment. A little over one-third of river miles, lake acres (excluding the Great Lakes), and estuarine waters assessed by the States were found to not fully support their designated uses in 1994 (table 2.2.1). The Great Lakes continue to suffer serious pollution, even though some progress has been made in reducing the worst cases of nutrient enrichment |