THE FATE AND TRANSPORT OF PHOSPHORUS THROUGH THE BEAVER VALLEY WETLANDS

  Renee Pasker, Ann Schwemm, Matt Musgrave and Ed Brown

   The intent of this project was to determine if the Beaver Valley Wetlands is removing phosphorus from its watershed prior to empting into Beaver Creek, which ultimately empties into the Cedar River.  Excess phosphorus can lead to eutrophication, which can indirectly cause many species to suffer due to lower oxygen levels.  To determine the fate and transport of phosphorus in the wetlands, the total phosphorus (TP) of both the water and sediments was measured and the ability for sediments to remove phosphate was determined.  The TP in the water column in the wetlands varied temporally from 700 to 1700 mg/L.  Dissolved inorganic phosphate (SRP) totals were usually low (20 mg/L) but a spike was observed after a rainfall event.  The levels of SRP in the water led to testing of the TP levels in sediments and TP sorption capabilities.  The TP of the sediment varied spatially from 500- 700 mg/gdw.  Sediments from Beaver Creek had total phosphorus levels of about 500 mg/gdw and the inlet to the wetlands varied from 300-400 mg/gdw.  Depending on soil type maximum sorption for wetland samples was from 2-9 mg/ g-dry weight.  Samples from both Beaver Creek and the inlet were about 7mg/gdw.  The results suggest that sediments in the Beaver Valley Wetlands are not yet saturated with phosphorus and therefore, when aerobic, can prevent phosphorus transport to rivers and streams.

  This research was supported by the Roy J. Carver Charitable Trust, the Iowa Space Grant Consortium and the Iowa State Water Resources Research Institute/United States Geological Survey.