How Healthy Are Our Rivers and Streams?
Series of Reports Show a Complex Picture
America's rivers and streams are generally suitable for irrigation, supplying drinking water, and home and recreational uses. However, in areas with significant agricultural and urban development, the quality of our nation's water resources has been degraded by contaminants such as pesticides, nutrients, and gasoline-related compounds.
These findings are highlighted in 15 reports on the health of major river basins across the country recently released by the U.S. Geological Survey (USGS). The reports complete a series of 51 area studies conducted by the USGS National Water-Quality Assessment (NAWQA) program.
For more than a decade, USGS hydrologists have looked at three questions related to water quality: What are the conditions of our nation's streams and groundwater? How is water quality changing over time? And how do natural features and human activities affect the quality of streams?
According to USGS Chief Hydrologist Robert Hirsch, "By evaluating and assessing our nation's water resources, we have a better understanding of water quality, and this gives us a comprehensive picture of the long-term health of America's rivers and aquifers. We have analyzed the effects of agricultural, urban, and forest land use practices on water quality, habitat, and biota."
Major challenges that continue to affect streams and groundwater are sources of pesticides, nutrients, metals, gasoline-related compounds and other contaminants. In urban areas, insecticides such as diazinon and malathion, which are commonly used on lawns and gardens, were found in nearly all of the streams that were sampled. Streams in agricultural areas were more likely to contain herbicides – especially atrazine, metolachlor, alachlor, and cyanazine.
Hirsch also noted that "concentrations of contaminants in water samples from wells were almost always lower than current EPA drinking water standards and guidelines. However, the possible risk to people, and to aquatic life, can only be partially addressed because of the lack of criteria for many chemicals and their degradation or -breakdown- products. In addition, criteria were developed for individual chemicals and do not take into account exposure to mixtures or seasonal high pulses in concentrations."
The detection of chemicals at low levels does not automatically translate into impacts on human or aquatic health. For example, USGS water quality assessments may be done at the parts-per-trillion levels, an amount that can be up to 100 times lower than the threshold used for setting standards and guidelines.
Other notable trends related to water quality over the past decade are:
• Changes in land management practices can improve water quality in streams over time. For example, changing from furrow to sprinkler and drip irrigation in parts of Washington's Yakima River Basin has reduced runoff from fields resulting in less sediment and compounds such as DDT in streams. In fact, concentrations of total DDT in large-scale suckers, smallmouth bass, and carp from the lower Yakima River decreased by about half since the 1980s.
• Even low levels of urban development have an impact. In Anchorage, for example, the abundance and diversity of aquatic insects became affected when about 5 percent of a watershed was converted into areas like parking lots.
• Natural features, such as soils, climate, and geology, are an important influence on water quality in watersheds. For example, mercury concentrations in fish are affected by the amount of wetlands and chemical properties of soils and water, and therefore, fish in forested streams in New England had higher levels of mercury than fish in the more urban watersheds in the Boston metropolitan area.
• Contaminants can occur naturally, even in relatively pristine areas like Wyoming, and Montana's Yellowstone River Basin. Elevated phosphorus concentrations were noted as derivatives from igneous and marine sedimentary rocks. Elevated arsenic levels are most likely from sedimentary rocks in contact with geothermal waters.
Findings from Colorado watersheds include:
• Upper Colorado River Basin. The major influences on rivers and streams in the Upper Colorado River Basin include urban development, abandoned or inactive mines and agricultural return flows. Most of the sampled streams and rivers met state and federal water quality guidelines, with some exceptions for trace element concentrations in the Southern Rocky Mountains and selenium concentrations in the Colorado Plateau. (Upper Colorado River Basin Report)
• Rio Grande Valley. Pesticides were detected in 94 percent of the sampled sites, though no pesticide concentrations in surface water exceeded EPA drinking water standards or applicable state or federal guidelines. Elevated trace element concentrations, which appear to be related to natural conditions and human activities, were found in some samples. Significant habitat degradation was found at six of 10 sampling sites. (Rio Grande Valley Report)
• South Platte River Basin. Water quality in the South Platte River Basin was found to be affected by a number of factors such as water development, mining, residential development in mountain areas, urban land use and agriculture. The cumulative effects of mixed (urban and agricultural) land use on water quality were found to be greater than that of exclusively urban or agricultural land uses. (South Platte River Basin Report)
Free copies of the NAWQA reports are available from 1-888-ASK-USGS, by fax 303-202-4693 or at http://pubs.water.usgs.gov/nawqasum/.
Series of Reports Show a Complex Picture
America's rivers and streams are generally suitable for irrigation, supplying drinking water, and home and recreational uses. However, in areas with significant agricultural and urban development, the quality of our nation's water resources has been degraded by contaminants such as pesticides, nutrients, and gasoline-related compounds.
These findings are highlighted in 15 reports on the health of major river basins across the country recently released by the U.S. Geological Survey (USGS). The reports complete a series of 51 area studies conducted by the USGS National Water-Quality Assessment (NAWQA) program.
For more than a decade, USGS hydrologists have looked at three questions related to water quality: What are the conditions of our nation's streams and groundwater? How is water quality changing over time? And how do natural features and human activities affect the quality of streams?
According to USGS Chief Hydrologist Robert Hirsch, "By evaluating and assessing our nation's water resources, we have a better understanding of water quality, and this gives us a comprehensive picture of the long-term health of America's rivers and aquifers. We have analyzed the effects of agricultural, urban, and forest land use practices on water quality, habitat, and biota."
Major challenges that continue to affect streams and groundwater are sources of pesticides, nutrients, metals, gasoline-related compounds and other contaminants. In urban areas, insecticides such as diazinon and malathion, which are commonly used on lawns and gardens, were found in nearly all of the streams that were sampled. Streams in agricultural areas were more likely to contain herbicides – especially atrazine, metolachlor, alachlor, and cyanazine.
Hirsch also noted that "concentrations of contaminants in water samples from wells were almost always lower than current EPA drinking water standards and guidelines. However, the possible risk to people, and to aquatic life, can only be partially addressed because of the lack of criteria for many chemicals and their degradation or -breakdown- products. In addition, criteria were developed for individual chemicals and do not take into account exposure to mixtures or seasonal high pulses in concentrations."
The detection of chemicals at low levels does not automatically translate into impacts on human or aquatic health. For example, USGS water quality assessments may be done at the parts-per-trillion levels, an amount that can be up to 100 times lower than the threshold used for setting standards and guidelines.
Other notable trends related to water quality over the past decade are:
• Changes in land management practices can improve water quality in streams over time. For example, changing from furrow to sprinkler and drip irrigation in parts of Washington's Yakima River Basin has reduced runoff from fields resulting in less sediment and compounds such as DDT in streams. In fact, concentrations of total DDT in large-scale suckers, smallmouth bass, and carp from the lower Yakima River decreased by about half since the 1980s.
• Even low levels of urban development have an impact. In Anchorage, for example, the abundance and diversity of aquatic insects became affected when about 5 percent of a watershed was converted into areas like parking lots.
• Natural features, such as soils, climate, and geology, are an important influence on water quality in watersheds. For example, mercury concentrations in fish are affected by the amount of wetlands and chemical properties of soils and water, and therefore, fish in forested streams in New England had higher levels of mercury than fish in the more urban watersheds in the Boston metropolitan area.
• Contaminants can occur naturally, even in relatively pristine areas like Wyoming, and Montana's Yellowstone River Basin. Elevated phosphorus concentrations were noted as derivatives from igneous and marine sedimentary rocks. Elevated arsenic levels are most likely from sedimentary rocks in contact with geothermal waters.
Findings from Colorado watersheds include:
• Upper Colorado River Basin. The major influences on rivers and streams in the Upper Colorado River Basin include urban development, abandoned or inactive mines and agricultural return flows. Most of the sampled streams and rivers met state and federal water quality guidelines, with some exceptions for trace element concentrations in the Southern Rocky Mountains and selenium concentrations in the Colorado Plateau. (Upper Colorado River Basin Report)
• Rio Grande Valley. Pesticides were detected in 94 percent of the sampled sites, though no pesticide concentrations in surface water exceeded EPA drinking water standards or applicable state or federal guidelines. Elevated trace element concentrations, which appear to be related to natural conditions and human activities, were found in some samples. Significant habitat degradation was found at six of 10 sampling sites. (Rio Grande Valley Report)
• South Platte River Basin. Water quality in the South Platte River Basin was found to be affected by a number of factors such as water development, mining, residential development in mountain areas, urban land use and agriculture. The cumulative effects of mixed (urban and agricultural) land use on water quality were found to be greater than that of exclusively urban or agricultural land uses. (South Platte River Basin Report)
Free copies of the NAWQA reports are available from 1-888-ASK-USGS, by fax 303-202-4693 or at http://pubs.water.usgs.gov/nawqasum/.
Photo by Gary Kramer, USDA Natural Resource Conservation Service
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Copyright 2004 League of Women Voters of Colorado Education Fund