Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: November 6, 2003
Publication Date: November 6, 2003
Citation: TOMER, M.D., MEEK, D.W., KRAMER, L.A., JAMES, D.E. RUNOFF AND BASEFLOW RELATIONSHIPS AS INFLUENCED BY MANAGEMENT AND TERRAIN. ASA-CSSA-SSSA ANNUAL MEETING ABSTRACTS. 2003. CD-ROM. MADISON, WI.
Long-term records from small watersheds can help determine how agricultural systems influence hydrology. In Iowa's Loess Hills, stream discharge from three similar, small watersheds (31-43 ha) was monitored from 1964 to 2001. Rainfall monitoring and hydrograph separations for each watershed allowed daily records of precipitation, runoff, and baseflow to be constructed. Our aim was to identify how management changes have effected change in the hydrologic records. Two of the watersheds were in continuous corn from 1964 until 1996, when one (W1) was placed in a corn-soybean rotation and the second (W2) in a six-year rotation including alfalfa (3 yr). The third watershed (W3) was pastured until 1972 and then placed in continuous corn under ridge tillage. Baseflow increased with time, but precipitation and runoff showed no clear long-term trend. W1 had 20% greater runoff and 17% less baseflow than W2, due to its steeper terrain (5.3 versus 4.2% average slope). Discharge from W2 (relative to W1) decreased after 1996, but the change in baseflow only become obvious after 3 years. W3 had the least runoff and greatest baseflow despite being of intermediate slope. Baseflow from W3 increased after conversion from pasture to cropland, from 9 to 28% of precipitation. Management period, terrain and long-term trends influence comparisons between watersheds.