Submitted to: Proceedings of the Symposium on Watershed Management
Publication Type: Proceedings
Publication Acceptance Date: April 1, 1995
Publication Date: August 14, 1995
Citation: Kuhnle, R.A., Bingner, R.L., Alonso, C.V. 1995. Changes in land use and sediment yield of fines. Watershed Management Planning for the 21st Century, T.J. Ward, ed., ASCE p 54-63. Interpretive Summary: Knowing the effect agricultural land use changes have on the erosion of soil from a land surface is critical information for making informed decisions on the preservation of soil resources. Previous studies have shown that for small areas land use is a critical factor in how much soil is eroded. In larger areas, however, many complex factors make the relation between land use and amount of soil erosion difficult to predict. The Goodwin Creek Experimental Watershed (GCEW) provides an excellent opportunity to calculate the effect of changing agricultural practices on the rate of soil loss for a relatively large area (21.3 square kilometers). Land use surveys of GCEW have been conducted annually since 1982. The percentage of land used for crop production on GCEW decreased from 23% in 1982 to 11% in 1990. Erosion rates, measured as a concentration of soil in the runoff, were less than 1/2 the rate of 1982 in 1991. More than 1/4th of this change has been attributed to changes in the percentage of cropland on the GCEW by using computer technology to predict the source of the erosion. Change in the erosion rates of the channels in the watershed, possibly from less frequent large storms, was the probable cause of the balance of the measured change
Technical Abstract: The Goodwin Creek Experimental Watershed (21.3 sq. km) is located in the bluff hills region of the north central region of Mississippi. Land use, rainfall, runoff and sediment data collected on the watershed from 1982- 1991 have shown that the percent of cultivated land and the concentration of fine sediments have decreased over the period 1982-1991, while runoff per unit of rainfall has remained largely constant. Land use of the Goodwin Creek Watershed was 51% pasture, 26% forest, and 23% cultivated when data collection was begun in 1982. By 1990 the land use of the watershed was 61% pasture, 28% forest and 11% cultivated. Over this period mean annual concentration of the fine (< 0.062 mm) sediment of the watershed has decreased from 2600 to 1200 ppm. Simulations from a sediment yield model indicate that approximately 26% of this change is from changes in land use with the rest attributable to changes in channel erosion on the watershed. One possible cause of the decrease in channel erosion may be the declining frequency of large runoff events on the watershed. This information is important when evaluating the effects erosion control practices may have on watershed systems.