Richard Zartman1, David Hammer2, Dewayne Mays2, and Steven Peaslee2. (1) PO Box 42122, Texas Tech University, Texas Tech. University, Plant and Soil Science Department, Lubbock, NE 79409-2122, (2) USDA/NRCS, 100 Centennial Mall N, Lincoln, NE 68508
The loss of
agricultural chemicals in runoff from agricultural land is a major cause of
poor surface water quality in the United State. Scientists (NRCS)
developed a technique to estimate the impact of agricultural watersheds on
natural water resources. The objective of this study was to apply this
technique on the Wagon Train (WT) watershed to predict loss of alkaline earth
elements (Ca, Mg, Ba, and Sr)
by runoff from soils, and to estimate elements loading into WT reservoir. The
predicted losses of Ca, Mg, Ba, and Sr by runoff were 67.5, 19.9, 0.17, and 0.05 kg/ha/yr,
respectively. These data give a total annual loss of 262.1 Mg Ca, and 77.1 mega
gram Mg for the entire watershed and could be considered as the annual loading
for WT reservoir. Lower values were predicted for Ba
and Sr. The total annual loss was 668 kg for Ba
and 186 kg for Sr and could represent the annual
loading for the reservoir. The predicted Ca, Mg, and Ba
concentrations in runoff were in good agreement with those observed in water
samples collected weekly from the main watershed's stream. However, the
predicted Sr concentration in runoff was much lesser
than that observed in the stream water. Subsurface seepage into the stream
might contribute to the high Sr concentration observed
in the stream water. We concluded that the technique could provide a reasonable
estimation of Ca,
Mg, and Ba losses in runoff from agricultural
watersheds and loading into surface water bodies.