Comparative Study of Transport Processes of Nitrogen, Phosphorus, and Herbicides to Streams in Five Agricultural Basins, USA
- Joseph L. Domagalski *a,
- Scott Atorb,
- Richard Coupec,
- Kathleen McCarthyd,
- David Lampee,
- Mark Sandstromf and
- Nancy Bakere
- a U.S. Geological Survey, 6000 J St., Sacramento, CA 95819
b U.S. Geological Survey, 8987 Yellow Brick Rd., Baltimore, MD 21237
c U.S. Geological Survey, 308 South Airport Rd., Jackson, MS 39208
d U.S. Geological Survey, 10615 S.E. Cherry Blossom Dr., Portland, OR 97216
e U.S. Geological Survey, 5957 Lakeside Blvd., Indianapolis, IN 46278
f U.S. Geological Survey, National Water Quality Lab., Denver Federal Center, Building 95, Lakewood, CO 80225
Agricultural chemical transport to surface water and the linkage to other hydrological compartments, principally ground water, was investigated at five watersheds in semiarid to humid climatic settings. Chemical transport was affected by storm water runoff, soil drainage, irrigation, and how streams were linked to shallow ground water systems. Irrigation practices and timing of chemical use greatly affected nutrient and pesticide transport in the semiarid basins. Irrigation with imported water tended to increase ground water and chemical transport, whereas the use of locally pumped irrigation water may eliminate connections between streams and ground water, resulting in lower annual loads. Drainage pathways in humid environments are important because the loads may be transported in tile drains, or through varying combinations of ground water discharge, and overland flow. In most cases, overland flow contributed the greatest loads, but a significant portion of the annual load of nitrate and some pesticide degradates can be transported under base-flow conditions. The highest basin yields for nitrate were measured in a semiarid irrigated system that used imported water and in a stream dominated by tile drainage in a humid environment. Pesticide loads, as a percent of actual use (LAPU), showed the effects of climate and geohydrologic conditions. The LAPU values in the semiarid study basin in Washington were generally low because most of the load was transported in ground water discharge to the stream. When herbicides are applied during the rainy season in a semiarid setting, such as simazine in the California basin, LAPU values are similar to those in the Midwest basins.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 2008.