From the first Americans to the present day, our people have lived in awe of the power, the majesty, and the beauty of the forest, the rivers, and the streams of America.
President Bill Clinton
Despite major droughts and chronic water shortages in some locales and record floods in others, the United States has an abundance of high-quality, fresh surface water and groundwater. In 1993 combined withdrawals from rivers, streams, lakes, reservoirs, and groundwater aquifers continued to meet U.S. needs for potable freshwater. Water issues centered on reauthorization of the Clean Water Act and the Safe Drinking Water Act. The Administration supports amendments that would provide better protection of our nation's water at a lower cost. Other issues ranged from joint U.S.-Canadian efforts to restore the Great Lakes ecosystem to U.S.- Mexican efforts to improve water quality in the Rio Grande River.
A number of federal agencies are involved in managing and protecting the nation's water resources. Within the Department of the Interior (DOI), the U.S. Geological Survey (USGS) provides the hydrologic information essential to these tasks. The Bureau of Reclamation (BOR) operates water projects to provide flood control, and water supplies to western states for irrigation, municipal and industrial use, hydropower, recreation, and fish and wildlife. Other DOI agencies, such as Fish and Wildlife Service and the Bureau of Land Management have programs to protect water quality and aquatic ecosystems. The U.S. Environmental Protection Agency (EPA) administers water pollution control and safe drinking water programs and, with the Army Corps of Engineers (COE), regulates the dredging and filling of wetlands and other coastal waters and ocean dumping. The COE also oversees a vast system of levees, dams, and reservoirs primarily for flood control, irrigation, hydropower, and navigation. Within the Department of Agriculture, the Soil Conservation Service administers swampbuster and wetlands reserve programs, and within the Department of Commerce, the National Oceanic and Atmospheric Administration (NOAA) conducts coastal and marine water quality assessments and supporting research. The NOAA also manages the nation's marine sanctuaries and estuarine research reserves. In addition many states assume principal administrative roles in managing water resources through programs delegated to them by the federal government.
Water resource issues tend to focus on either quantity and/or quality for surface water or groundwater. Hydrologic distinctions between surface water and groundwater are far from absolute, with groundwater supplying an estimated 40 percent of average annual baseflow to streams.
Among the good news, the nation is not running out of water, and total water use is below estimates. Periods of above-normal precipitation, however, will likely follow periods of drought, in the future as in the past. Water-related events in 1993, which were a study in contrasts, support this contention. The prolonged 1987-1993 drought that affected much of California, Arizona, and other western states appeared to end only to be followed by winter floods on the Gila and Tijuana rivers; then summer came with record floods that devastated the Mississippi and Missouri river basins.
In 1993 the renewable (long-term) supply of water in streams and aquifers was estimated to be 1,400 billion gallons per day for the conterminous United States. Offstream withdrawal of surface water continued to be the primary source of the nation's water supply, but groundwater, as it has since 1950, continued to gain in favor as an additional source. Groundwater, the source of drinking water for over half the U.S. population and for most rural residents, increased in use for all purposes except thermoelectric power generation where water is used in the generation of electricity by steam turbines.
The factors determining whether a community uses surface water or groundwater as its freshwater source differ across the country. The largest withdrawals of fresh surface water occurred in California, Idaho, Illinois, Michigan, Ohio, and Texas. Together eight states withdrew more than 10 billion gallons of freshwater per day for offstream uses, accounting for 41 percent of the total surface water withdrawals in the nation. States with the largest fresh groundwater use are in the West where irrigated agriculture is common.
Despite projections that U.S. water use would increase, total offstream and instream uses declined in 1985 compared to 1980. In 1990 although total offstream use rose 2 percent above 1985, it remained 8 percent less than earlier projections. For most water- use categories, a general slackening in the rate of increase changed to a decrease in water use between 1980 and 1985. Two exceptions are thermoelectric power plants, which in 1990 used the greatest share with 48 percent of total withdrawals, and public water supplies that accounted for only 9.4 percent of the total.
A 4-percent increase in total withdrawals for thermoelectric power from 1985 to 1990 was the result of a 15-percent increase in saline water withdrawals. This water is used for cooling purposes, with most of it returned to the source. Instream water used for hydroelectric power generation remained a major nonconsumptive use of managed water systems.
Even though the U.S. population increased 4 percent between 1985 and 1990, withdrawal and consumptive- use increased only 2 percent during this time, in part due to increasing efforts for water conservation, improved efficiency of water use, and use of water- reuse technology. These figures contrast the 1970-1975 figures, when the rate of increase in withdrawals more than doubled the rate of population growth.
The exploration and development of the United States has relied on surface water. Today surface water continues to be the major source of water for municipal and industrial use, irrigation, and generation of electricity. Rivers, lakes, and reservoirs also provide recreational opportunities for tens of millions of people each year and support fisheries and wildlife habitat.
The hydrologic cycle-the continual circulation of water from the sea to the atmosphere to the land and back again-determines the natural availability of surface water in any geographic area. This availability depends ultimately on the amount of rain and snow an area receives. Average annual precipitation in the United States is 30 inches per year; however, the range varies from a few tenths of an inch per year in desert areas of the Southwest to 400 inches per year at sites in Hawaii.
The standard measure of water quantity, whether offstream or in- stream and whether for recreation, irrigation, or public water supplies, is streamflow. The USGS 6-year streamflow trend data for October 1988-September 1993 illustrate the variation in natural distribution of water supplies across time and space. The hydrograph for the United States and Southern Canada shows that monthly streamflow for 1993 was well above the long-term median streamflow for the 30-year period 1961-1990. Streamflow amounts in many of the 12 hydrologic basins monitored by the USGS also were in the above-normal range, especially in the upper Mississippi River basin, which includes the Missouri River. In contrast streamflow has been below normal in the Northwest for most of the past several years.
Floods occur when weather deviates strongly from the long-term climate pattern and delivers more water to land surfaces than can be readily absorbed or stored.
The Midwest Flood of 1993. The single most damaging flood event of the year was -the Great Midwest Flood. This protracted event began setting itself in motion in January with development of abnormally high soil moisture levels in the Upper Midwest and a significant snowpack. Moderate flooding from heavy rains in April and May aggravated the situation. In late June an extraordinarily stable and extremely wet weather pattern established itself over the Midwest, producing intense rains over Iowa, Missouri, Minnesota, Wisconsin, Illinois, Kansas, Nebraska, and North and South Dakota. The rains continued through July and August, and produced record floods over much of this 9-state area. Flood waters overtopped, undercut, and breached over 1,000 levees, flooding thousands of acres of land and hundreds of homes, structures, and buildings.
The rainfall over the upper Midwest from May to August 1993, unmatched in the historical records of the central United States, was approximately 200-350 percent of normal for the northern plains southeastward into the central Corn Belt. The precipitation totals were remarkable not only in magnitude but also in their broad regional extent: record wetness existed over 260,000 square miles. With wet antecedent conditions which caused waterlogged soils, the water from the heavy rains had no place to go other than into the streams and river courses. The result was record flooding which equaled or exceeded flood recurrence intervals of 100-years along major portions of the mid-Mississippi and lower Missouri rivers. In terms of precipitation amounts, record river stages, flood duration, areal extent of flooding, persons displaced, crop and property damage, and economic impact, the Midwest Flood of 1993 surpassed all previous U.S. floods. Flood damages in the nine affected states are estimated at $15.6 billion, but fortunately the number of deaths was relatively low: 38 people died as a direct result of flooding.
Winter Floods In the Southwest. On January 19, 1993, the President declared the entire state of Arizona a flood disaster area. The excessively wet 1992-1993 winter, while beneficial to Arizona and California in breaking their longstanding drought, led to heavy runoff that caused the severe flooding, dam overtopping, agricultural and other property damage, and loss of life. Flood warnings were in effect almost continuously from January through April for the middle and lower Gila River. Among the forecast locations monitored by the National Weather Service, 14 experienced record flows, but the most deadly flooding occurred on the Tijuana River, along the border between California and Mexico.
For the first time since it was constructed in 1960, the Painted Rock Dam on the Gila River, 50 miles southwest of Phoenix, filled to capacity (2.6 million acre-feet or 113 percent of flood control capacity) and had an uncontrolled spill. All upstream reservoirs on the Gila, Salt, and Verde rivers also filled and spilled through their emergency spillways. The uncontrolled flow out of the Painted Rock Reservoir resulted in flooding as far downstream as Mexico and led to the evacuation of 3,500 people. Total damages from the southwest winter floods were $392 million ($228.9 million in Arizona and $163.7 million in California), with 17 deaths attributed to the flood.
Flood Risk Reduction. As a result of 1993 floods and the damage and loss of life that occurred, the effectiveness of the traditional levee-drainage-diversion approach to alleviating flood risk in flood-prone basins is under review. In 1993 the Administration formed several interagency working groups to consider alternative ways to reduce flood risks in the future, such as programs that protect, restore, and enhance wetlands, thus reducing the rate of inflow from the watershed, and movement of dwellings out of hazard zones. For example hazard mitigation projects funded by the Federal Emergency Management Agency following these recent flooding disasters are removing development from floodplains and restoring some areas of the floodplains to open space and natural areas.
In the fall of 1993 the White House chartered the Scientific Assessment and Strategy Team to develop a database of flood and basin information at the EROS Data Center in Sioux Falls, South Dakota. The White House also appointed the Administration Floodplain Management Task Force to make recommendations on changes in current policies, programs, and activities of the federal government that most effectively would achieve risk reduction, economic efficiency, and environmental enhancement in the floodplain and related watersheds.
At the other extreme from floods, droughts can severely reduce water availability and cause significant environmental impacts and economic hardships. The adverse effects of a drought on water supplies depend on the following factors:
. Amount of water stored or available from the preceding year;
. Water demands relative to average flow;
. Soil conditions;
. Natural flow during a drought period; and
. Drought-stressed vegetation that retard recovery of soil moisture until its deficit is satisfied.
The multi-year droughts of the late 1920s and l930s resulted in extensive regional impacts. For the past several years, river basins throughout the western region have experienced drought conditions.
Snow Water Equivalents. About 75 percent of the useable water in the western states originates as mountain snowfall. This snow accumulates during winter and spring and remains for as much as 9 months before it melts and appears as streamflow. Measured by snow water equivalents, snowpack is the most relevant factor in determining water supply in the West. Fall precipitation influences soil moisture prior to the formation of the snowpack and explains, in part, the effectiveness of the snowpack in producing runoff. Soil moisture condition has been traditionally measured by the Palmer Drought Severity Index (PDSI), but is now also reported as a Surface Water Supply Index calculated from existing soil moisture conditions, snowpacks and precipitation, and expectations in several western states.
Water-Deficit Areas. Throughout the 19th and most of the 20th centuries, water management focused on acquiring additional water supplies to meet the needs of expanding populations and associated economic development in water-deficit areas. Much of this need was met by damming rivers and storing water in reservoirs during times of high flow. Engineering advances in the construction of high dams and the generation of hydroelectric power enabled the transportation of large amounts of water over great distances to irrigate arid lands and meet water demands of growing cities in the West and Southwest. Parts of the country, especially in the West and Southwest, have begun to face the physical limits of water resources. Large-scale development of water resources in the near future is unlikely because in many locations, the best reservoir sites are already developed. Construction costs and concerns about the environmental impacts of dams also call into question the feasibility of additional development. Continued growth in these regions will require some combination of importing water and using and managing water more efficiently.
Storage Impoundments. Water supplies in storage impoundments were affected by the drought which gripped much of the West and Midwest from 1987 through 1992. In most drought areas, water supplies reached critically low levels. The unprecedented flooding that occurred along the upper Mississippi and lower Missouri rivers essentially ended the drought in the Missouri basin. In 1993 the Columbia River in Washington, Idaho, and Oregon and the drainages of the Sierra Mountains in California and Nevada remained the only major areas of persistent drought in the nation.
Water Year 1993 (October 1, 1992, through September 30, 1993) began with poor reservoir storage and poor soil moisture conditions. Some reservoirs had less than half of average storage after several years of drought in much of the West.
Central Valley Project of California. The Central Valley Project began the water year with 51 percent of average storage.
Nevada, Oregon, and Washington. Reservoirs in these states were in exceptionally poor condition, including those in the Humboldt River basin of Nevada and the Yakima River basin of Washington.
Southwest. The areas with good to excellent water supply were the Rio Grande basin of New Mexico, the Salt River basin of Arizona, and most of Texas.
Great Plains. A number of reservoirs in the Great Plains area had extremely high reservoir contents and had to evacuate water to provide space for flood storage. The upper portions of the Great Plains were affected by the weather patterns that produced the flooding in the Mississippi and Missouri rivers. Most reservoirs filled to capacity and remained full. In addition soil moisture conditions were extremely wet during the summer of 1993.
Snow Water Equivalents. Though it fluctuated as the year progressed, the February 1 snow water equivalent showed average to well above average snowpack in much of the West. The southern half of the region had exceptionally high snowpacks and forecasted inflow. Exceptions to this pattern were found in portions of the Northwest and Montana.
Streamflow Forecasts. These forecasts reflected the same fluctuating pattern with some accounting for dry soil moisture conditions. In general this pattern of snowpack and streamflow forecasts prevailed through the snow season into May when the last forecasts are made.
Palmer Drought Severity Index. End-of-year PDSI data showed most areas of the West with adequate to excellent soil moisture, and end-of-year water supply conditions showed most areas with good to excellent carryover reservoir storage.
Groundwater is available nearly everywhere in the United States, although the quantity available and the conditions controlling its occurrence differ from region to region. Maximum average well yields occur in the Columbia Lava Plateau (Washington, Oregon, Idaho, California, and Nevada) and the southeastern Coastal Plain. The smallest yields generally are in the western mountain ranges. Groundwater pumping has increased steadily during the past several decades, with changes in water table levels in wells reflecting changes in the amount of groundwater in storage. In certain areas long-term withdrawals of large volumes of groundwater, primarily for agriculture, have resulted in widespread declines in water levels by 40 feet or more. Where the decline in water level took place many years ago, some areas have had their water table stabilize at a lower level. In other areas reduced water levels are relatively recent events. Development trends, such as in the following areas, suggest the need to conserve existing groundwater supplies if the nation is to meet future water needs.
Arizona and California. In water-deficit areas such as Arizona and California, large volumes of groundwater continue to be withdrawn to meet agricultural and municipal needs. Because of limited supplies, such withdrawals cannot be sustained indefinitely. Groundwater mining in the California San Joaquin Valley has resulted in sediment compaction and land subsidence.
Florida. Groundwater development in Florida has redistributed natural flow patterns in the aquifers, resulting in sinkholes, saltwater intrusion, and land surface subsidence.
Although the federal government administers a significant portion of the nation's water storage and conveyance facilities, water allocation and administration rests principally with the states. The Army Corps of Engineers and the Bureau of Reclamation, through the operation of their projects, provide water supplies to the states.
The Army COE manages over 600 water management projects nationwide, and the BOR, which manages the majority of projects in the West, operates more than 350 reservoirs. These projects provide water resources for municipal and industrial use, irrigation, hydroelectric power, flood control, navigation, recreation, and fish and wildlife.
Water conservation is a major element of the BOR water resources management program. The BOR and the Soil Conservation Service signed a Memorandum of Agreement in 1993 that lays the foundation for the two agencies to collaborate in carrying out water conservation projects. During the year the BOR provided technical assistance and training to states and water users in the West to improve water use efficiency and to develop water conservation plans. Examples include the following projects:
Klamath Project. The BOR provided water users and interested parties with a drought plan, identified water use priorities, suggested water conservation activities, provided water allocation projections, and hosted a drought survival seminar.
Northwest Salmon Recovery Projects. In the Pacific Northwest, the BOR cooperated with interest groups in selecting four demonstration projects for salmon recovery: the Snake River Flow Augmentation Project and three Tributary Enhancement Water Conservation Projects.
Water quality began to emerge as an issue following World War II. It took several decades of growing concern, but the 1972 amendments to the Federal Water Pollution Control Act, commonly known as the Clean Water Act, created the nation's landmark environmental legislation. The act and its amendments have improved water quality in surface waters that receive discharges from municipal wastewater treatment plants and industrial facilities. State governments and industry responded to regulations that control the discharge of pollutants into waterways by reducing discharges, becoming more efficient in water use, reducing the production of wastes, and improving the recycling of waste products. The Safe Drinking Water Act introduced measures to prevent contamination of drinking water supplies.
Efforts to further improve water quality will focus more on the reduction of pollution from diffuse, nonpoint sources, such as agricultural and urban runoff and contaminated groundwater discharges. In most cases nonpoint sources of pollution are hard to control and costly to treat. Preventing pollution is the preferred strategy for reducing nonpoint-source discharges.
Water quality in the nation's rivers and streams either improved or remained about the same during the 1980s as shown by most available measures. Although modest improvements in water quality during this period of economic and population growth represent a significant achievement in pollution control, much remains to be done to reach existing water quality goals for the indicators currently monitored at the national level. Moreover data on biological and toxicological aspects of river and stream water quality are limited, leaving the questions of progress in these areas largely unanswered.
From among the available surface water quality indicators, three types of national or regional data have been analyzed by the USGS: selected chemical, physical, and sanitary constituents or properties of water; toxic trace elements and pesticides in finfish tissues; and herbicides. The results of these analyses were published by the USGS in 1993.
These include fecal coliform bacteria, total phosphorus, dissolved oxygen, nitrate, suspended sediment, and dissolved solids.
Fecal Coliform Bacteria and Total Phosphorus. Notable improvements occurred in concentrations of fecal coliform bacteria, an important indicator of the suitability of streamwater for contact recreation. About 12 percent of monitoring stations showed decreased coliform concentrations. Total phosphorus, usually the nutrient controlling eutrophication in freshwater, also showed improvement, with about 20 percent of stations showing decreased phosphorus. Nationally the percentage of water quality monitoring stations having fecal coliform bacteria and total phosphorus concentrations greater than desirable limits also decreased during the 1980s. Despite widespread declines in these indicators, however, more than a third of the streams sampled in 1989 had annual average concentrations that exceeded desirable limits.
Dissolved-Oxygen Concentrations. Overall about 10 percent of stations showed increased concentrations of dissolved oxygen from 1980 to 1989. This improvement could reflect the effect of improving point-source controls.
Nitrate Concentrations. Nitrate concentrations and yields remained nearly constant nationally, but they declined in a number of streams draining agricultural areas where nitrate levels have been historically high. This general tendency toward constant or declining concentrations represents a significant departure from the pattern of trends for 1974 through 1981, when widespread increases in nitrate were reported. Nitrogen supports eutrophication, an aging process that slowly fills a body of water with sediment and organic matter and alters basic characteristics such as biological productivity, oxygen levels, and water clarity. The quantity of nitrate transported to coastal waters, where nitrogen supports eutrophication, decreased in the Gulf of Mexico area but increased somewhat in the North Atlantic and California coastal areas during the 1980s.
Suspended Sediment Concentrations. About 10 percent of stations showed decreased suspended sediment concentrations. The quantity of suspended sediment transported to coastal waters decreased or remained the same in all but the North Atlantic region.
Dissolved Constituents. Some change was noted in concentrations of dissolved constituents that have economic significance through their effects on the aesthetic characteristics of drinking water, the chemical characteristics of industrial process water, or the salinity of irrigation water. About 12 percent of stations showed decreased dissolved solids from 1980 to 1989, and annual average concentrations of dissolved constituents exceeded desirable limits at a third or fewer of the sampled streams. The most noteworthy changes were substantial decreases in the chemical corrosivity of stream water used for domestic and industrial water supplies.
National information documenting trends in the toxicological aspects of fresh water is limited to data on toxic contaminants in finfish tissue in major rivers and the Great Lakes. Contaminant concentrations in finfish tissue are an integrative measure of water quality and can reflect long-term average contaminant concentrations in stream water and sediment. The data show that, since the 1970s, concentrations declined significantly for arsenic, cadmium, lead, chlordane and related organic compounds, dieldrin, DDT and related compounds, toxaphene, and total PCBs (polychlorinated biphenyls). Concentrations of mercury, however, remained nearly constant during the same period.
Although national trends data for pesticides in stream water are not available, recent studies of herbicide concentrations in streams in agricultural areas of the midwestern United States (1989-1993) provide regional information on the magnitude and distribution of herbicides in streams. In a 1989 study atrazine exceeded applicable EPA drinking water criteria at 52 percent of the streams sampled during the first runoff following herbicide application. For alachlor, cyanazine, and simazine, the number of streams sampled that exceeded the criteria ranged from 2 to 49 percent. Substantially lower but detectable concentrations of these herbicides persisted throughout the year in many of the streams in the region. Subsequent sampling for these herbicides in the Mississippi River and its tributaries in 1991 and 1992 showed that atrazine and alachlor occasionally exceeded EPA drinking water criteria and that substantial quantities of these herbicides are transported by major rivers over long distances.
During the Great Flood of 1993, extraordinarily large amounts of agricultural chemicals were flushed into the Mississippi River, many of its tributaries, and ultimately, into the Gulf of Mexico. The flooding did not dilute the concentrations of herbicides as was anticipated. Instead larger-than-average amounts were flushed into streams, and the daily loads transported by some reaches were higher than those previously measured. For example the maximum daily load of atrazine transported by the Mississippi River in the vicinity of Thebes, Illinois, during the flood of 1993 was as much as 70 percent higher than that measured in 1991. The total load of atrazine discharged into the Gulf of Mexico from April to August 1993 was about 80 percent larger than the same period in 1991 and 235 percent larger than this same period in 1992.
The EPA cooperates with states, territories, tribes, commissions, and the District of Columbia (collectively referred to as the states) to conduct a biennial water quality inventory as required by Section 305(b) of the Clean Water Act. For the 1992 EPA National Water Quality Inventory (finalized in 1993), 642,881 miles or about a fifth of total U.S. river miles, including nonperennial streams, canals, and ditches, were assessed.
Designated Uses. The inventory found that 56 percent of assessed river miles fully support designated uses, and an additional 6 percent support uses but are threatened and may become impaired if pollution control actions are not taken. Another 25 percent of assessed river miles partially support designated uses, and 13 percent do not support them. Only 125 miles (less than a tenth of 1 percent) of the assessed waters could not attain designated uses. The states also assessed support of six individual designated uses in rivers and streams: aquatic life support, fish consumption, primary contact recreation such as swimming, secondary contact recreation such as boating, public drinking water supply, and agricultural water supply. Of the 221,352 river miles assessed for drinking water supply use, 27 percent could not attain drinking water use standards.
Source of Impairment. More than one source can contribute to impaired water quality. Agricultural runoff is the leading source of pollutants in rivers and streams. Other sources far less frequently reported include municipal point sources, urban runoff and storm sewers, and resource extraction such as mining. Loss of wetlands also can contribute to water quality problems. Without wetlands to trap sediments and pollutants, contaminants would otherwise be discharged into surface waters through runoff from adjacent lands.
Chief Pollutants. Pollutants resulting from runoff included siltation, pathogens, toxic chemicals, and excess nutrients. Such pollutants can produce low dissolved oxygen levels capable of suffocating fish and contaminating groundwater. Siltation and nutrients impair more miles of rivers and streams than any other pollutants, affecting 45 percent and 37 percent of impaired stream miles respectively. Other leading causes of impairment include pathogens, pesticides, organic enrichment, and resultant low levels of dissolved oxygen.
Lakes are sensitive to pollution inputs because they flush out their contents relatively slowly. Even under natural conditions, lakes undergo eutrophication or aging, which alters basic lake characteristics. Human activities can accelerate eutrophication by increasing the rate at which nutrients and organic substances enter lakes from their surrounding watersheds. Runoff from agricultural, urban and construction sites, leaking septic tanks, sewage discharges, eroded streambanks, and similar sources can enhance the flow of nutrients and organic substances into lakes. These substances stimulate the growth of algae and aquatic plants, creating conditions that interfere with the health and diversity of indigenous plant, fish, and other animal populations and the recreational use of lakes. Enhanced eutrophication from nutrient enrichment due to human activities is one of the leading problems facing the nation's lakes.
For the lake section of the 1992 EPA National Water Quality Inventory, 49 states assessed 46 percent (18.3 million acres) of U.S. lakes, ponds, and reservoirs. Overall 43 percent of the assessed lake acres fully supported uses such as swimming, fishing, and drinking water supply. An additional 13 percent were identified as threatened and in need of pollution control actions. Another 35 percent of assessed lake acres partially supported designated uses, and 9 percent did not support designated uses. The leading causes for lake water impairment in 1992 were nutrients, organic enrichment/dissolved oxygen depletion, metals, siltation, and priority organic chemicals (PCBs). The state data portray agriculture as the most specific source of pollution in the nation's lakes, followed by urban runoff and storm sewers, hydrologic and habitat modification, municipal point sources, and onsite wastewater disposal.
Acidic lakes are generally found in areas where watershed soils have limited buffering capabilities. Acid rain or acid mine drainage can depress the pH levels of a lake to the point at which many forms of aquatic life are stressed or eliminated. Increases in lake acidity can also increase the solubility of toxic substances and magnify their adverse effects. Results of the National Acid Precipitation Assessment Program (NAPAP) studies indicate relatively few serious acidification problems in the nation's lakes.
Oligotrophic: Clear water with little organic matter or sediment and minimum biological activity.
Mesotrophic: Waters with more nutrients and therefore more biological activity.
Eutrophic: Waters extremely rich in nutrients, with high biological productivity. Some species may be choked out.
Hypereutrophic: Murky, highly biologically productive waters, closest to the wetlands status. Many clearwater species cannot survive.
Dystrophic: Low in nutrients, highly colored with dissolved humic organic matter. Not necessarily a part of the natural trophic progression.
The EPA Environmental Monitoring and Assessment Program (EMAP) began piloting the EMAP-Surface Waters Program with a study of northeastern lakes in New England, New York, and New Jersey in 1991. Chlorophyll-a, which is a surrogate measure of algal biomass, and total phosphorus concentrations from the lake pilot study indicate the degree of nutrient enrichment in the lakes:
Classification Nutrient Enrichment
Oligotrophic lakes 38
Mesotrophic lakes 42
Eutrophic and Hypertrophic lakes 21
When statistically aggregated into three ecoregions-the Adirondacks, the New England Uplands, and the Coastal/Lowland/Plateau regions-the data show different spatial patterns in lake quality.
By area the Great Lakes ecosystem contains the world's largest body of surface freshwater. Once endowed with a natural abundance, the Great Lakes had seas of freshwater, splendid forests, plentiful animals, rich soils, immense wetlands, and multitudes of waterfowl; but three centuries of development have taken their toll. The passenger pigeon became extinct early in the 20th century, exterminated by hunting and the loss of oak and beech forest habitat. Few of the once plentiful sturgeon survive, and lake trout populations are not self-sustaining. The bald eagle breeds with less success along the shores of the lakes than inland, while habitat available to other birds, fish, and wildlife is greatly reduced, as are their populations.
Recognizing these problems, the United States and Canada have achieved, over the past 30 years, encouraging successes. They have reduced phosphorus loadings to the lakes, abated excessive algae in Lake Erie, protected fish populations from sea lamprey, and restored oxygen-depleted waters. Although large industries have reduced their toxic discharges, they still release significant amounts of hazardous substances. While levels of some targeted toxic contaminants have declined in fish and wildlife, improving the health of many species, considerable levels of toxics remain in sediments in harbors leading into the lakes, and the Great Lakes ecosystem faces a range of new and enduring environmental challenges.
In 1993 the EPA, in cooperation with eight states-Illinois, Indiana, Michigan, Minnesota, New York, Pennsylvania, Ohio, and Wisconsin-proposed a water quality guidance program to protect the Great Lakes ecosystem. The program will establish minimum water quality criteria, antidegradation procedures, and implementation procedures for the Great Lakes basin with emphasis on bioaccumulative pollutants. The result would be consistent, basin-wide water quality standards for the protection of human health, aquatic life, and for the first time, wildlife. The initiative-a milestone in addressing environmental problems on an ecosystem basis-is a critical element of the U.S.-Canadian effort to protect and restore the water resources of the Great Lakes, which are experiencing the following problems.
Contaminated Fish and Wildlife. The Great Lakes food web remains contaminated by a variety of bioaccumulated toxic substances with unacceptable levels in some fish and wildlife. Levels are much lower than in the 1970s but still justify fish consumption advisories, usually directed at PCBs, mercury, and chlordane. Contaminants have been associated with health problems in 15 Great Lakes fish and wildlife species. Effects have usually been most pronounced at the top of the food web and across generations, as expressed in birth defects. Other documented fish and wildlife problems include loss of appetite and weight, hormonal changes, poor reproductive success, tumors, increased susceptibility to disease, and behavioral changes. With the significant decline in contaminant levels, many species seem to be recovering. Problems persist for fish and wildlife in certain locations, particularly in harbors and rivers with highly contaminated sediments, and for predators high in the food web, such as lake trout, mink, and bald eagles. Contaminant levels are generally higher in Lake Michigan and Lake Ontario, which have longer water retention times than the other lakes, though these lakes have also experienced the greatest declines in contaminant levels during the past two decades.
Contaminated Bottom Sediments. Bottom sediments in many harbors and rivers of the Great Lakes ecosystem contain a variety of bioaccumulated toxic substances, indicative of past loadings of contaminants to the lakes. Contaminated sediments are associated with tumors in bottom fish; they serve as a reservoir of contaminants that recycle into the food web through resuspension or uptake by bottom-dwelling organisms and injure such organisms. Contaminated sediments greatly increase the costs of navigational dredging owing to the added costs of handling and disposing of toxic materials. In some locations contamination has delayed navigational dredging for years and curtailed waterborne commerce.
Diminished Wetlands. More than half the Great Lakes wetlands have been lost since 1800. Chicago, Detroit, and Milwaukee stand on former wetlands. The present rate of destruction is much less than in prior eras, but development pressure continues to threaten remaining wetlands.
Exotic Species. More than 130 exotic (nonnative) species have been introduced to the Great Lakes since 1800, nearly a third carried in by ships. Some exotics have profoundly damaged native species. A troublesome recent invader, the zebra mussel, probably entered the lakes via ballast water discharge from an oceangoing vessel. The full impacts of the mussel are not yet known, but they are potentially great. A prolific breeder, the mollusk devours microscopic plants at the foundation of the food web and may create a food shortage for fish that graze on these plants, ultimately threatening predator fish such as walleye, salmon, and lake trout. Colonies also foul and clog water intake pipes to water treatment and power plants.
Depleted Native Fish Populations. Prior to settlement in the Great Lakes basin, over 170 species of fish existed in the lakes. Lake sturgeon lived up to 90 years and lake trout up to 75 years. Fish populations today are drastically different than those found in the 1800s, a result of food chain disruptions, overfishing, and habitat loss and disruption, such as drained wetlands, silted-over spawning beds, and dams that impede upriver passage. Add to these competition from nonnative species, for instance, alewife displacing lake herring and sea lamprey feeding on large fish. Great Lakes fish today are smaller, live shorter lives, and survive in sometimes substantially reduced numbers.
. Threat to Native Species. The damage to once richly abundant native fish populations is profound. Lake herring was once the predominant forage fish. Sturgeon grew six feet in length and weighed more than 100 pounds. Today sturgeon and lake herring survive in much depleted numbers. Hatchery-reared lake trout must be stocked to maintain ecological balance and to sustain sport and commercial fisheries. Stocked nonnative Pacific salmon-coho and chinook-are now the most abundant top predators, except in western Lake Erie where the top predator is walleye, but their fate may hinge on the availability of alewife, their principal and preferred forage. The chinook salmon began to decline in the mid 1980s, at least in part because of an increase in the incidence of bacterial kidney disease, a phenomena often seen in large fish culture programs. Walleye in western Lake Erie may be threatened by the zebra mussel which, because of its extraordinary filtration capacity, is changing the fundamental character of the aquatic plants, insects, and zooplankton. The new flora and fauna favor pike and bass species that favor walleye fry as a food source.
. Sea Lamprey Control. Some progress to improve fish resources has been made. Sea lamprey control has resulted in the reestablishment of deepwater fish populations, like whitefish in northern Lake Michigan. Such control programs remain essential to their survival. The stocking of lake trout and Pacific salmon that help to restore the predator/prey relationships in fish communities have permitted the growth of commercial and sport fishing industries.
Excessive Phosphorus. Since 1970 phosphorus detergent restrictions, municipal sewage treatment plant construction and upgrades, and agricultural practices that reduce runoff have cut the annual phosphorus load to the Great Lakes by half. The decline in phosphorus loadings is most evident in Lake Erie, which receives more effluent from sewage treatment plants and sediment from agricultural lands than any other Great Lakes. In the late 1960s, Lake Erie was infamously clogged by foul-smelling mats of algae that depleted dissolved oxygen from bottom waters by their seasonal die-off and decay. Lake Erie is also experiencing concurrent decline in phytoplankton biomass and decline in the rate of oxygen depletion of the central basin, each an indicator of improving trophic condition. Phosphorus levels in the open waters of Lakes Superior and Michigan have been reduced to levels below those set as objectives in the Great Lakes Water Quality Agreement of 1978. Phosphorus levels in Lakes Huron, Erie, and Ontario continue to exceed the objective slightly. Nonetheless, nutrient enrichment continues to be a problem in many nearshore waters of all the Great Lakes except Lake Superior, especially shallow waters that receive agricultural runoff or areas with a high surrounding population such as Lake Erie, Lake Ontario, Saginaw Bay, and Green Bay.
Designated Uses. For the EPA 1992 National Water Quality Inventory, the states found toxic contamination to be the most prevalent and persistent water pollution problem facing the Great Lakes. Virtually all of the waters along the Great Lakes shoreline fail to fully support overall designated uses. Priority organic chemicals, such as PCBs and dioxins, are the most prevalent cause of impairment in Great Lakes waters.
For most of this century, land surface and subsurface disposal of wastes was considered safe and convenient. Only recently did researchers discover that natural processes have a limited capacity to convert contaminants into harmless substances before they reach groundwater. EPA research suggests that over half the nation's land area has geologic factors that would allow groundwater contamination and that 1 percent (68,500) of all U.S. drinking water wells exceed the EPA health-based limits on contaminants.
In the late 19th and early 20th centuries, industrial and agricultural wastes contaminated many of the rivers and streams that supplied drinking water for urban populations. Widespread contamination of drinking water sources eventually led to laws that required government intervention, such as the Safe Drinking Water Act (SDWA). Under this act the EPA sets standards for drinking water quality and requirements for treatment. Federal standards control both anthropogenic and naturally occurring contaminants, and the Public Water Supply Supervision Program, authorized by the SDWA, supervises compliance. In most cases states have the primary responsibility for oversight and enforcement. The EPA supports states through grants and technical assistance and, if necessary, enforces SDWA regulations.
Drinking water can still be a source of harm to human health, however, especially in the following areas:
. Where aquifers have been contaminated by septic systems, leaking storage tanks, and chemical releases,
. Where agricultural chemicals contaminate surface water and groundwater, and
. Where compounds leak from underground storage tanks or chemical dumps.
Direct exposure to these agents can occur when contaminated water supply is used for drinking, cooking, bathing, swimming, or washing utensils used for cooking or eating. Even with safe water supplies that have been adequately treated, contamination by infectious and toxic agents can occur when agents are reintroduced into plumbing or distribution systems by cross-connections in sewage lines, infiltration through waterline breaks, or through leaching of toxic substances, such as lead, from the plumbing system. Water can affect human health indirectly when people consume crops irrigated with contaminated water, or when they eat fish, shellfish, or aquatic plants grown in contaminated water.
In 1993 drinking water supplies were generally safe from bacterial contamination and usually free of gross contamination or obvious chemical pollution. The most severe health effects from contaminated water, such as cholera and typhoid fever, have been essentially eliminated in the United States by chlorination and filtration of drinking water. Yet other hazards still remain. Contaminants of increasing concern over the last 20 years have been radionuclides, lead, chlorine-resistant microbial contaminants, pesticides, toxic chemicals, and by-products of the disinfection process. Of the 200,000 water systems in the United States, thousands fail to comply with the Safe Drinking Water Act.
The proportion of U.S. homes served by public and private water suppliers and public sewers has increased since 1970. In 1991 of the 104 million homes in the United States, 85 percent received water from public water systems or private water suppliers, and 76 percent were served by public sewers. The remaining homes obtained water from wells (13 percent) or other water supplies (2 percent) and used septic tanks, cesspools, chemical toilets, or other means (24 percent) for sewage disposal.
Using complete plumbing-hot and cold piped water, flush toilet, and a bath or shower-as another indicator of access to safe water and sanitation, the nation has upgraded the quality of housing significantly. In 1940 half of U.S. housing units lacked complete plumbing, but by 1990, this percentage had declined to only 1.1 percent. In 1990, nonetheless, a million U.S. houses remained without complete plumbing.
Housing units in metropolitan areas are more likely to have access to complete plumbing than units in rural areas, and persistent low- income counties traditionally have had the lowest access of any rural county type. The more remote rural counties in the South and the West, especially Arizona, New Mexico, and Alaska, had 3 percent of their housing units without complete plumbing in 1990. A major factor in western rates of incomplete plumbing is the long distances between houses and municipal water and sewer systems. In Alaska long distances combined with permafrost in many areas restrict the availability of water and sewer systems. Many southern counties with persistent low incomes also have limited access to complete plumbing.
The 1992 EPA National Pesticides Survey estimated that 10.4 percent of community water supply wells and 4.2 percent of rural domestic wells contain detectable levels of one or more pesticides. A more recent report from Illinois indicates that 12 percent of the private wells surveyed in the state had detections of at least one pesticide or pesticide degradate. Elevated levels of nitrates also have been frequently detected in groundwater. These and other groundwater contaminants, such as organic and inorganic chemicals, radionuclides, and microorganisms may cause adverse health, social, environmental, and economic impacts. Among these impacts are the health risks of exposure to contaminants and expenditures such as groundwater purification systems. Because groundwater provides baseflow to streams, the potential for adverse impacts on surface- water quality also exists, especially under conditions where dilution is minimal.
Lead is a highly toxic metal that can have adverse health affects, including interference with red blood cell formation, reduced birth weight, mental retardation, and premature birth. The Safe Drinking Water Act requires public water systems to sample drinking water from taps in areas where higher lead levels are expected to be found and to report lead concentrations to the state or EPA.
Monitoring Requirements. In 1992 the EPA required large public water supply systems, those that serve more than 50,000 people, to conduct lead monitoring in two periods, from January to June and from July to December. Medium public water supply systems, those serving between 3,301 and 50,000 people, were required to conduct monitoring from July to December 1992. In results, released by the EPA in 1993, of the 6,483 large and medium systems conducting monitoring at the end of the year, 819 systems exceeded the lead action level of 15 parts per billion in 10 percent of their samples. These systems provide drinking water to 30 million people nationwide. Small systems, those that serve less than 3,300 people, comprise 90 percent of all drinking water systems nationwide and provide service to 10 percent of the U.S. population. These systems were required to initiate lead monitoring in 1993.
Protective Measures. Under the SDWA public water systems exceeding the lead action level are required to take the following measures to protect public health: Install corrosion control measures to reduce lead levels; perform additional monitoring; inform the public of elevated levels; and offer information on how to minimize drinking water lead exposure.
For more than two decades, the Centers for Disease Control and Prevention (CDC) and the EPA have carried out national surveillance of waterborne disease outbreaks associated with water intended for drinking, recreational water use, and outbreaks on cruise ships. Although the program involves voluntary reporting of disease outbreaks and may thus underestimate such outbreaks, it continues to be a useful means of characterizing the changing epidemiology of waterborne diseases. It helps identify the types of water systems, the water system deficiencies, and the etiologic agents associated with outbreaks. Although waterborne diseases in the United States are not associated with as much morbidity and mortality as they were earlier in this century, outbreaks continue to occur, sometimes even in relatively sophisticated community water systems.
The number of outbreaks of waterborne diseases in water intended for drinking has declined since the 1970s, although the relative proportions of outbreaks attributed to various types of water supplies and etiologic agents have remained fairly stable. The decrease in reported outbreaks may represent an actual decrease in the number of occurrences or a decrease in the recognition or reporting of outbreaks. Despite the smaller number of outbreaks reported in recent years, some incidents have been extensive. For example, a cryptosporidiosis outbreak in Georgia in 1987 affected 13,000 people and, more recently, one in Milwaukee in 1993 affected 403,00 people. In both cases, people became ill with gastroenteritis after consuming water from a public water supply. Nonetheless, most disease outbreaks are associated with noncommunity or small community water systems, which may reflect the fact that large cities tend to have more sophisticated water systems. To prevent waterborne transmission of such diseases as Giardia, Cryptosporidium, and other infectious agents, the EPA has prepared guidelines for filtration and disinfection of all public water systems using surface water sources.
Giardia lamblia and Cryptosporidium. Giardia is the most commonly implicated protozoan parasite in outbreaks of waterborne disease. Many such outbreaks are associated with ingestion of chlorinated but unfiltered surface water and surface-influenced groundwater. Filtration is necessary to remove Giardia from water; chlorination alone is insufficient without high concentrations and long contact times. Cryptosporidium, also a protozoan parasite and even more chlorine-resistant than Giardia, was implicated in other recent outbreaks.
Shigella sonnei. In outbreaks caused by the most commonly implicated bacterial pathogen, Shigella, water supplies were found to be contaminated with human waste.
The major water quality accomplishment of 1993 was the ongoing groundwork in Congress for reauthorization of the Clean Water Act and the Safe Drinking Water Act.
The goals of the Clean Water Act are fishable, swimmable rivers throughout the nation and zero discharge of pollutants into U.S. navigable waters. The act requires all municipal sewage and industrial dischargers to obtain a permit before discharging into waterways. Permits usually require dischargers to reduce or remove pollutants from their wastewater before discharge. It provides federal grants and capitalization of state revolving load funds to help communities build sewage treatment plants. The EPA and the states cooperate to establish limits on the amounts of specific pollutants that may be discharged by point sources such as municipal sewage treatment plants and industrial facilities. They base minimum discharge limits on available and economically achievable technologies, but also require higher levels of treatment for dischargers to water quality limited waterbodies.
During Congressional hearings on the major reauthorization issues, the Administration maintained that the statute is fundamentally strong but suggested the following changes:
. Stronger enforcement provisions,
. Increased emphasis on integrated wetlands and watershed management,
. More effective controls for reducing nonpoint-source and toxic pollution, and
. Increased funding for pollution control programs.
Reauthorizing the Safe Drinking Water Act
Debate over reauthorization of the Safe Drinking Water Act (SDWA) continued in 1993, and the Administration made the following recommendations to strengthen the act and the ability of the states to maintain sound drinking water programs:
. A drinking water state revolving loan fund to assist local water systems in meeting SDWA requirements;
. A user fee system to provide states with additional resources needed to maintain state drinking water programs;
. Source water protection mechanisms to prevent contamination;
. An improved process for determining which contaminants should be regulated by EPA and how soon they should be regulated;
. Flexibility in complying with statutory requirements;
. More efficient and stronger enforcement; and
. Special assistance for small systems.
Many communities that rely on groundwater as a source of drinking water are confronted with contamination. Once contamination occurs, remediation is time-consuming and resource-intensive, and in some cases may be technologically infeasible. If groundwater is the sole source of drinking water, communities may be forced to rely on bottled water for years. To avoid this hardship, many communities are concentrating on preventing contamination. In 1993 the EPA supported pollution prevention activities by working through the states and directly with citizen groups to empower communities with the ability to protect their groundwater resources. Examples of EPA efforts follow.
State Groundwater Protection Programs. The EPA is working with the states to develop Comprehensive State Ground Water Protection Programs to coordinate federal and state programs. Coherence is necessary to establish successful community groundwater pollution prevention efforts. In 1993 the EPA issued guidance that will assist states in developing a strong prevention-oriented groundwater program. The guidance provides a framework for a strong federal-state alliance, with the goal of a fully-integrated, comprehensive groundwater protection effort.
Wellhead Protection Programs. Thirty-seven states and territories have an EPA-approved wellhead protection program. While state programs are necessary, the actual tools to prevent contamination are usually found at the city, township, county, and multi- county/regional level. Local governments may be the only appropriate level of government to conduct some prevention activities, such as regulation of local land uses. To support local efforts to protect drinking water supplies, the EPA has worked with states and communities to develop local as well as state wellhead protection programs. Focused on protecting a community's underground sources of drinking water by delineating the groundwater resources around the community's well, these programs identify the potential sources of contamination that could affect groundwater and the appropriate actions to ensure that resources are protected. By the end of 1993, EPA estimates that 18,000 communities have initiated some level of wellhead protection, but only an estimated 4,500 of the communities are operating complete protection programs.
Under the Clean Water Act, the EPA or approved states administer the National Pollutant Discharge Elimination System (NPDES). The agency and 40 approved states issue permits that establish effluent limits for all municipal and industrial dischargers. In addition to technology-based limits, the EPA may develop limits based on water quality criteria where technology-based controls are not stringent enough to make waters safe for such uses as fishing, swimming, and drinking. Stringent EPA standards for industrial dischargers control up to 126 toxic pollutants. Currently EPA has developed effluent limitation quidelines, based on the best available technology that is economically feasible, for 50 major industries. These guidelines establish minimum discharge limits for industrial dischargers to control nutrients, toxics, and other pollutants.
In 1993 the EPA took the following actions to address the most significant remaining source of water quality impairment-wet weather runoff-the culprit of nonpoint-source pollution:
Nonpoint-Source Management. In January of 1993, EPA released in technical guidance for coastal states that provides a foundation for reducing nonpoint-source pollution, a problem associated with the degradation of many estuaries in the United States (See Chapter 3: Wetlands and Coastal Waters).
Combined Sewer Overflow Policy. Combined sewer overflows (CSOs) occur where sanitary and storm sewers are interconnected. During rainstorms combined sewer systems become overloaded and discharge a multitude of pollutants associated with sanitary sewage, industrial wastewater, and polluted runoff into local receiving waters. These discharges can cause exceedances of water quality standards that pose risk to human health, threaten aquatic life and its habitat, and impair the use and enjoyment of aquatic resources. To reduce these impacts, the EPA is expected to issue a national policy on assessing and controlling CSO discharges through the National Pollutant Discharge Elimination System (NPDES) in the spring of 1994. The policy, to be developed in collaboration with state and local governments, environmental groups, and other interested parties, will include guidance for developing appropriate, site'specific NPDES permit requirements and enforcement initiatives to ensure compliance as soon as practicable.
Stormwater Controls. The Clean Water Act requires a NPDES permit for all stormwater discharges from industrial facilities, and in 1993 EPA proposed a mechanism to assist industries in their efforts to control discharges and comply with Clean Water Act requirements. A multisector general permit, proposed for 29 industrial categories, would provide 45,000 facilities with an alternative to resource-intensive individual permits. The EPA developed the multisector permit in consultation with, and using data submitted by, the affected industries themselves.
Toxic contamination of surface water and sediments is a major problem in some areas, posing risk to human health, aquatic life, and the environment. The EPA completed a final rule to establish numeric criteria for as many as 98 toxic pollutants in 12 states and two territories that failed to adopt water quality standards for such pollutants as required by the Clean Water Act. Water quality standards, normally adopted by the states and territories, are the keystone for all water pollution control programs. The National Toxics Rule, the largest EPA standards-setting action to date, demonstrates the agency's commitment to act when states fail to adopt standards that meet Clean Water Act requirements. The rule will remain in effect until the states and territories adopt and receive EPA approval of their own water quality standards.
Although hundreds of billions of dollars have been spent by government and the private sector on water pollution abatement since the 1970s, the lack of a comprehensive, integrated national monitoring and reporting system makes it difficult to assess the effectiveness of these investments in achieving the goals and objectives of the Clean Water Act. To remedy these shortcomings, an Intergovernmental Task Force on Monitoring Water Quality (ITFM) undertook a comprehensive review and evaluation of ambient water quality monitoring in the United States. Twenty federal and state agencies with water quality monitoring responsibilities took part. The first-year report of the task force, issued in 1992, concluded that a comprehensive, well-integrated strategy is essential to understand the condition of the nation's water resources and to provide a basis for policies to assure the wise use and management of these resources. The task force concentrated on developing the -building blocks- needed to implement a national water quality monitoring strategy.
During 1993 the ITFM undertook a pilot study in Wisconsin to test various task force recommendations. State and federal agencies concentrated on jointly sampling selected sites and comparing agency methods to determine the magnitude of differences in measurement results and their causes. The study will be expanded in 1994.
The Tennessee Valley Authority (TVA) is committed to establishing the Tennessee Valley as a model of sustainable development economically and environmentally. In addition to managing the TVA reservoir system to provide minimum flows for aquatic life and lake levels suitable for recreation, the TVA is committed to protecting and improving the health of the Tennessee River.
River Action Teams. The TVA approach to river cleanup builds partnerships for watershed protection and improvement. River Action Teams-small, self-directed teams of water resource specialists-are at work in four subwater sheds of the Valley. The teams identify and develop cooperative projects to solve pollution problems and protect aquatic resources. The TVA has plans to assign teams to all 12 subwatersheds in the Valley.
Cleanup Mechanisms. Between 1991 and 1993, the TVA took the following actions:
. Installed aeration systems to increase dissolved oxygen levels in releases from seven of its dams;
. Reclaimed 300 acres of land around the Copper Hill mine site in Tennessee;
. Helped implement best management practices on 60 farms in the eastern part of the Valley;
. Supported 10,000 hours of volunteer cleanup efforts on streams, rivers, and lakes; and
. Increased public awareness of water resource conditions by publishing the award-winning River Pulse, a colorful report card on the health of the Tennessee River.
The people of the Tennessee Valley have different needs and goals, influenced by watersheds that often cover more than one state and multiple counties, but the TVA outreach experience demonstrates that government agencies can accomplish far more by working with others than by working alone.
The United States and Mexico continued their collaborative efforts to improve water quality along the Mexico border in 1993. Both countries took part in joint monitoring along the Rio Grande River and planned to begin groundwater sampling. Work continued on a design for an international wastewater treatment facility in Tijuana. The two nations signed an international agreement to provide wastewater treatment service to the Mexico/Calexico area and drafted an agreement for industrial wastewater pretreatment in the Nogales area.
Goolsby, D.A., W.A. Battaglin, and E.M. Thurman, Occurrence and Transport of Agricultural Chemicals in the Mississippi River Basin, July Through August 1993, U.S. Geological Survey Circular 1120-C, (Washington, DC: GPO, 1993).
International Joint Commission, Seventh Biennial Report on Great Lakes Water Quality, (Windsor, Ontario: IJC, 1994).
Michigan Department of Natural Resources, State of the Great Lakes: 1993 Annual Report, (Lansing, MI: MI, DNR Office of the Great Lakes, 1993).
Mills, E.L., J.H. Leach, J.T. Carlton, and C.L. Secor, -Exotic Species in the Great Lakes: A History of Biotic Crises and Anthropogenic Introductions,- J. Great Lakes Res. 19(1):1-54 (1993).
Moody, D.W., -Water: Freshwater Resources of the United States,- Research & Exploration, (Washington, DC: National Geographic Society, 1993).
National Geographic Society, Water: Reflections on a Critical Resource, (Washington, DC: National Geographic Society, 1993).
Solley, W.B, R.R. Pierce, and H.A. Perlman, Estimated Use of Water in the United States in 1990, U.S. Geological Survey Circular 1081, (Washington, DC: GPO, 1993).
U.S. Army Corps of Engineers, U.S. Army Corps of Engineers Annual Flood Damage Report to Congress for Fiscal Year 1993, (Washington, DC: USACE, April 1994).
U.S. Department of Commerce, Bureau of the Census, American Housing Survey, Current Housing Reports Series H-150'91 , (Washington, DC: DOC, BOC, 1991).
U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, -Waterborne Disease Outbreaks - United States, 1991-1992,- Morbidity and Mortality Weekly Report 40(SS-5):1-22, (Atlanta, GA: HHS, PHS, CDC, November 19, 1993).
U.S. Department of the Interior, Bureau of Reclamation, Water Conservation Directory, (Washington, DC: DOI, BOR, April 1993).
U.S. Department of the Interior, U.S. Geological Survey, National Water Conditions, (Reston, VA: DOI, USGS, monthly).
National Water Summary 1990-91: Hydrologic Events and Stream Water Quality, U.S. Geological Survey Water-Supply Paper 2400, (Washington, DC: GPO, 1993).
U.S. Environmental Protection Agency, National Water Quality Inventory: 1992 Report to Congress, (Washington, DC: EPA, Office of Water, March 1994).
The Quality of Our Nation's Water: 1992, (Washington, DC: EPA, Office of Water, March 1994)
A Report to Congress on the Great Lakes Ecosystem, (Washington, DC: EPA Great Lakes National Program Office, February 1994).
Annual Report of the Council on Environmental Quality (1993)
Chapter 1: Air Quality and Climate
Chapter 2: Water Quantity and Quality
Capter 3: Wetlands and Coastal Waters
Chapter 4: Conservation Farming and Forestry
Chapter 5: Public Lands and Federal Facilities
Chapter 6: Ecosystem Approach to Management and Biodiversity
Chapter 7: Energy and Transportation
Chapter 8: Risk Reduction and Environmental Justice
Chapter 9: Environmental Economics
Chapter 10: National Environmental Policy Act
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