An Analysis of the Water Situation
in the United States: 1989-2040

A technical supporting document for the 1989 RPA Assessment



The United States has abundant supplies of fresh water. The renewable water supply of the coterminous United States amounts to about 1,400 billion gallons per day (bgd). Aggregate daily withdrawals amount to 343 bgd or 25% of renewable supply. Aggregate daily consumption amounts to 93 bgd or 7% of renewable supply.

The Nation's watersheds are generally in good condition. But special attention must be given to managing the soil and vegetation on more than 70% of our watersheds to maintain or improve the quality and quantity of water flowing from them. A survey of watersheds in the U.S. revealed that 28% are in prime condition; 50% require special consideration of soil and vegetation characteristics when resource management plans are prepared; and 22% require direct capital investments to restore watershed conditions to a level consistent with resource management goals. Most watersheds in prime condition are in the West; most special emphasis watersheds are in the South and North; and most watersheds requiring direct capital investments are in the North and Rocky Mountains.

There are 90 million acres of wetlands remaining in the coterminous United States, less than one half the acreage that existed 200 years ago. Wetland losses are continuing at an alarming rate, estimated at 350,000 to 500,000 acres annually. The principal reason for the continued decline in wetlands is conversion to urban, suburban, and agricultural land uses.

Concerns about water shortages in the United States arise because water supplies are unevenly distributed in relation to the regional and seasonal distribution of water demands. Water resource development has been the preferred way of increasing water availability, but future large scale developments are unlikely due to economic and environmental costs. A total of 480 million acre-feet of storage exists in the 2,654 largest reservoirs and controlled natural lakes with capacities greater than 5000 acre-feet; fifty thousand smaller reservoirs exist and have capacities between 50 and 5000 acre-feet. In addition, there are 2 million smaller ponds.

Other methods of increasing water availability have been tried, such as weather modifications, recycling wastewater, and reducing leaks, seepages, and evaporation. Recycling was touted in the mid-1970s as having great potential, but it is no more popular today than back then.

Acid deposition, erosion, and groundwater contamination are three important water related environmental problems. All three arise due to externalities - resource management actions that fail to take full account of potential disruption to ecosystems caused by pollutants.

A relative abundance of good quality surface water still exists. However, serious water-quality problems have developed in some stream reaches and some streams cannot support the full range of desired uses. Programs resulting from the 1972 Clean Water Act have made significant progress in cleaning up point-source pollution. For example, total biochemical oxygen demand declined for both municipal and industrial dischargers between 1972 and 1982 (46% and 71% respectively). Monitoring studies have found widespread decreases in fecal coliform bacteria and lead concentrations. Phosphorus concentrations have also declined, but to a lesser extent.

Nonpoint-source pollution has become more prevalent and its importance better understood as point-source pollution has been cleaned up. Monitoring studies show widespread increases in nitrate, chloride, arsenic, and cadmium concentrations. Suspended sediment and nutrients from agricultural sources are the most damaging nonpoint-source pollutants nationally.


The rates of increase in demand experienced from the mid-1950s to the mid-1970s have slowed. Freshwater withdrawals in the South and Rocky Mountain increased (85% and 75% respectively) at twice the rate of increases in the North and Pacific Coast regions (42 and 37% respectively). Irrigation is both the largest withdrawal use and the largest consumptive use. Thermoelectric steam cooling withdrawals have been growing most rapidly in recent years and are now almost equivalent to irrigation, but consumption is much lower.

Shortages (the situation where demands exceed supplies) are projected by 2040 for the Lower and Upper Colorado River, Rio Grande, Great Basin, California, and Lower Mississippi River Valley. Off stream water users will find water unavailable or there will be insufficient instream flows remaining to provide good survival habitat for fish, wildlife, and other instream uses. Water surpluses exist, even in dry years, in most regions east of the Great Plains and in the Pacific Northwest.

Four common themes emerge from the analysis of projected surpluses and deficits:

1. The impetus to resolve deficits will come from a desire to mitigate adverse impacts on fish, wildlife, and recreation uses caused by low instream flows.

2. Irrigation is the predominant consumptive use in each region where deficits occur. Consequently, eliminating deficits will require a reduction in projected rates of growth in irrigation water consumption.

3. Non-structural approaches, such as modifications in water rights institutions and freer functioning of water markets, will play a dominant role in solving the water supply deficits.

4. Water yield augmentation by vegetation management, building snow-trapping structures, and weather modification can help remedy small deficits. However, these techniques are unlikely to be employed as the dominant way of eliminating major regional deficits.

Water quality in 2040 will be somewhat better than current quality because nonpoint-source pollution abatement efforts are just beginning to bear fruit. But water quality will be somewhat lower than the baseline levels for forests and rangelands because some sites will undergo short-term disturbances.

Alternative futures have been briefly analyzed. If demand for water grows faster than in recent years, so that total demand is 20 percent higher than projected for 2040, deficits will emerge sooner and be more severe. If global climate changes produce average annual temperatures 2 degrees C warmer and precipitation is 10% lower, renewable supplies are projected to be from 5 to 40% lower, depending on the region. Deficits occur everywhere except in the Lake States and Northeast and are often severe, given projected future demands.


If recent patterns of water and related land resource use continue to 2040, there will be significant adverse environmental, economic, and social implications for American society. Avoiding the adverse consequences of these implications creates an impetus for changing soil and water resource management in the near future. A continuation of recent trends will:

* Reduce fish and wildlife habitat and populations and other instream uses, such as recreation.

* Lead to increased salinity causing disruptions in local economies relying upon surface water resources for potable supplies, and those relying heavily on irrigated agriculture and the processing, sale, and transportation of irrigated crops and products;

* Lead to significant additional reductions in waterfowl populations and reduction in fishing, hunting, and other recreational benefits;

* Lead to expansion of urban and suburban areas at the expense of prime agricultural land and wetlands;

* Lead to water shortages that will cause major social impacts on local residents and their communities and increase the cost of food for humans and livestock; and

* Lead to intensive groundwater mining.


Many opportunities exist for changing watershed management practices on all types and sizes of ownerships to help avoid environmental, social, and economic implications of water shortages. Only through the coordinated efforts of all landowners can the use of water and related resources reach their full potential.

Major opportunities to protect minimum instream flow levels exist through administrative controls and state water rights procedures.

Major opportunities for improving watershed condition exist through increasing emphasis on maintaining water quality through vegetation management; managing run-off timing through vegetation management, snow-trapping structures, and weather modification; increasing emphasis on improving riparian areas to keep pollutants out of streams and to provide cover for fish and wildlife; and increased opportunities to enhance soil productivity through consideration of chemical and biological aspects of soils in addition to soil physical characteristics.

Nonstructural measures, such as zoning flood plains to restrict certain types of development, provide state and local officials with the biggest opportunity for flood damage reduction.

Silvicultural nonpoint-source pollution abatement practices are well-developed; however, many opportunities exist to educate landowners about these practices and to apply them more consistently. Opportunities include better pre-harvest planning; better planning, design, and construction of roads; less soil-disturbing techniques for harvesting, storage, and hauling procedures; closure and revegetation of temporary roads and landings not needed after harvest; and careful application of fertilizers and pesticides.

Legislative changes recently implemented in the Food Security Act of 1985 and expected increases in crop yields present major opportunities to reverse the trend in loss of wetlands.


There is political resistance in some regions to free markets for water. Water institutions are giving high priority to off stream uses to the detriment of instream uses such as fish and wildlife habitat and recreation.

Information that accurately assesses current watershed and stream channel conditions and capabilities on all ownerships has not been consolidated. Further, information available is often not displayed to managers in ways useful to evaluate management impacts or plan rehabilitation of watersheds in poor condition.

Private landowners lack incentives to implement best management practices to reduce nonpoint-source pollution.

Income and property tax laws and regulations encourage wetlands conversion. There are few incentives to encourage private landowners to manage wetlands for wildlife and recreation benefits to society.

Large-scale water yield augmentation entails significant environmental and social risks.


The challenge for forest and rangeland mangers is to preserve the volume and quality of water for instream flows that promote fish and wildlife habitat and recreation and that will also satisfy emerging municipal needs in the next century.

The role of vegetation management, snow-trapping structures, and weather modifications for increasing water supplies could be reconsidered. Although these practices have been extensively researched, social acceptability of implementing them over wide areas and their role in expanding regional supplies has not been clearly decided.

Institutional barriers have been erected in many areas that prevent a market for water from emerging, or where one has emerged, that constrain it from functioning efficiently. Freer functioning of water markets can help reduce shortages.

Recent gains in agricultural productivity are going to decrease the nation's reliance on irrigation. In addition, society's preferences for water use are changing because demographic shifts are reducing the number of agricultural voters. Consequently, municipal supplies and adequate instream flows are becoming more important to society than increased irrigation use.

Maintaining and improving water quality will become a top priority for land managers. Because municipalities prefer to pay the cost of transporting clean water long distances instead of the cost of cleansing nearby water to potable standards, municipalities outside the traditional bailiwick of the resource manager may become vitally interested in land and water management issues.

Private landowners need education and technical and financial assistance to help them make the most of their opportunities to improve water quality, to restore and protect riparian areas, and to reduce downstream flood damages.

Long-term data is an important tool for studying complex ecological problems such as acid deposition. Background information on how the ecosystem functioned before the problems emerged is also essential to determine true effects. A system of sites for long term ecological monitoring needs to be established and monitoring begun.

Additional research is needed on cumulative effects of changes in land ownership and land management objectives as applied temporally and across a watershed.

Additional research is needed on maintaining soil productivity. Work to predict vegetation growth and harvestable outputs as a function of site characteristics is in its infancy. The nutritional needs of agricultural crops and effects of nutrition on yields are much better understood. Similar kinds of information are needed for forest and rangeland species.

Guldin, Richard W. 1989. An analysis of the water situation in the United States: 1989-2040. General Technical Report RM-177. Fort Collins, CO: U.S. Department of Agriculture, Rocky Mountain Forest and Range Experiment Station. 178 p.