(Beyond Pesticides, May 26, 2004)
In agricultural and urban areas, the quality of our nation’s water resources has been degraded by contaminants such as pesticides, nutrients, and gasoline-related compounds, according to Water Quality in the Nation’s Streams and Aquifers-Overview of Selected Findings, 1991-2001 released earlier this month. Based on a series of 51 United States Geological Survey (USGS) reports on the health of major river basins across the country (15 of which were also released earlier this month), the overview states that insecticides such as diazinon and malathion were found in nearly all of the streams that were sampled in urban areas. Streams in agricultural areas were more likely to contain herbicides-especially atrazine, metolachlor, alachlor, and cyanazine.
For more than a decade, USGS hydrologists have looked at three questions related to ground and surface water quality. What are the conditions of our nation’s streams and ground water? How is water quality changing over time? And how do natural features and human activities affect the quality of streams? According to the 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.”
Hirsch 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 51 reports on water quality were conducted since 1991 by the USGS National Water Quality Assessment (NAWQA) program. Of the 51 areas studied in the first phase of the program, the USGS has already launched a second round of studies in 42 areas to determine trends, fill critical gaps in the characterization of water-quality conditions, and increase understanding of natural and human factors that affect water quality.