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Originally published in Planning for an Uncertain Future—Monitoring, Integration, and Adaptation. U.S. Geological Survey Scientific Investigations Report 2009-5049. Credit U.S. Geological Survey Department of Interior/USGS

Abstract

Karst regions are composed of soluble rock, often limestone, which leads to the formation of fissures, sinkholes, and water flow conduits such as caves. Pollutants in karst waters tend to be quickly directed and concentrated into these subsurface conduits. As a result of this and other factors, water resources are especially sensitive to contamination and pollution in karst areas. Pollutant concentrations going into karst subsurface fluvial systems are often very similar to the concentrations surfacing at outlets such as springs. Areas connected by karst conduit flows must be distinctly determined and special attention should be given to water quality impacts from land-use practices near conduit inputs. The climate which affects a certain karst area can also have different impacts on water resources considerations. In the temperate climate of southwest Kentucky precipitation is mostly evenly distributed throughout the year. Southwest China is affected by a monsoon climate with high precipitation in the spring to summer and drier conditions in other seasons. In the wet season large storm pulses can effectively transport contaminants to water sources resulting in unhealthy loads, while the dry seasons can be particularly severe in karst areas as water quickly drains to the subsurface, making water access a major hardship. Our research focuses on the seasonal differences that the climate of southwest China poses for water quality, including differences in pesticide concentrations between agricultural and residential areas hydrologically linked by karst conduits. In late 2007 the fluvial connections in a simple karst system near Chongqing were confirmed using dye tracing techniques. The concentration of pesticides in agricultural runoff going into and coming out of the subterranean stream studied were within safe limits. Results supported that there was a close relationship among concentrations of the pesticides glyphosate, chlorothalonil, and atrazine in the input and the output of the system. Taking into account the rapid and direct flows in the karst system, the concentrations of the pesticides found in the output was more similar to the input than would be expected in a surface stream. Analysis of hydrology data of the site will be required before further conclusions can be developed. The research was conducted in the spring and summer of 2007–2008 and funded by the U.S. Agency for International Development.

Disciplines

Geology | Geomorphology | Hydrology

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