ASABE Technical Library - Abstract

Abstract.

Nutrient and sediment loading from streambanks are a growing concern within many watersheds. However, there are few studies on streambank phosphorus (P) concentrations and spatial distributions in watersheds. The objectives of this research included (i) quantifying the magnitude of and spatial distribution of streambank P concentrations along a stream system in a watershed with historical poultry litter application, (ii) quantifying the amount of water soluble phosphorus (WSP) and total phosphorus (TP) entering the stream from streambanks, and (iii) comparing streambank P concentrations and loading between two unique streams in the same ecoregion. Soil samples were taken along Spavinaw Creek in eastern Oklahoma and were processed to measure pH, electrical conductivity (EC), WSP, and TP. The pH and EC increased with distance from the confluence at Lake Eucha. There was no clear longitudinal trend in WSP and TP. Using estimated sediment loading (727 x 10⁶ kg) from aerial images, it was estimated from 2003-2013 there was 2.4 x 10² kg WSP and 1.5 x 10⁵ kg TP loaded into Spavinaw Creek from streambanks in Oklahoma. LOADEST, a nutrient load estimator created by the United States Geological Services (USGS), was used to estimate in-stream phosphorus loads. In-stream estimates were an order of magnitude larger for WSP and comparable for TP. A previous study performed a similar analysis along Barren Fork Creek (BFC) in the Illinois River watershed. Both Spavinaw Creek and BFC flow through the Ozarks ecoregion and have cherty topsoil with an underlying gravel layer. Comparison of P loading between the two systems showed that WSP in BFC was an order of magnitude higher while TP was on the same order of magnitude. Streambank P loading rates are dependent on the stream system; therefore each stream needs to be individually studied in order to gain a better understanding of the specific loadings from streambanks.