WWRC 87-13
The Effect of Beaver Ponds on the Nonpoint Source Water Quality of a Stream In Southwestern Wyoming
Abstract
Currant Creek, a second order stream in southwestern Wyoming, has three large complexes
of beaver ponds midway along its 32 km length. To determine whether these ponds improve the quality
of water flowing through them, during spring and summer of 1984 and 1985 water samples were taken
upstream from, within, and downstream from the pond complexes. During periods of high flow (i.e. springrunoff),
concentrations of suspended solids (SS), total phosphorus (TP), sodium hydroxide-extractable
phosphorus (NaOH-P, an index of biologically available P) and total Kjeldahl nitrogen (TKN) were
reduced in water flowing through the beaver ponds. During low flow, beaver ponds had less effect on these
parameters. Concentrations of nitrate nitrogen (NO3,-N) were reduced during both high and low flows,
while concentrations of ortho-phosphate (ortho-P) did not appear to be affected by beaver ponds.
Ammonia nitrogen almost always was at the limit of detection. Regression of NaOH-P versus [SS plus
ortho-P] suggested that the primary source of NaOH-P was SS. In general, SS explained a large portion
of the variation in TP, TKN, and NaOH-P, and often ortho-P was significantly correlated to TP. The
increase in the concentration of most parameters below the area with dam complexes appears to reflect
input from bank and channel erosion, and export of SS, TP, TKN and NO3-N from beaver dam
complexes was calculated to be less than that from stream sections above or below the dams. Thus the
location of dams should be considered before using them to try and improve water quality. The apparent
importance of bank and channel erosion as the primary source of nutrients to Currant Creek contrasts
with many watersheds in agricultural areas.
Key words—phosphorus, bioavailable phosphorus, nitrogen, erosion, nonpoint source pollution, water-
shed, mitigation
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