Submitted to: Research Day Abstracts: Regional Universities Research Day
Publication Type: Abstract Only
Publication Acceptance Date: 10/1/2003
Publication Date: 11/14/2003
Citation: Maddox, S.M., Sheth, N., Daniel, J.A., Elmendorf, D.L. 2003. Use of surface impoundments for the removal of fecal bacteria and nutrients from agricultural runoff. Research Day for Regional Universities. p. 93.
Interpretive Summary: Abstract Only.
Technical Abstract: The general public is becoming increasingly concerned over possible down-stream water quality impacts associated with livestock grazing. Surface impoundments, generally used to control downstream sediment movement, may prove beneficial in reducing pathogens and nutrients in surface water generated by livestock. Two grazed watersheds were studied over a two and a half-year period to determine their role in removing fecal bacteria and nutrients. Each watershed contained three successive surface impoundments, both with grazed winter wheat pastures and native rangeland, but one was further impacted by effluent from a small (+350 head) dairy operation. Water samples were collected monthly from the inlet and outlet of each surface impoundment and a location 0.5 km upstream from the first impoundment (i.e., source inlet). The samples were analyzed for nitrate-nitrogen (NO3-N), water-soluble phosphorus (WSP), bio-available phosphorus (BAP), fecal and total coliforms (FC and TC), and heterotrophic bacteria (HC) counts. Results showed that NO3-N concentrations were below 10 mg/L for both watersheds, and that downstream concentrations changed little. In the "dairy" watershed, there was a 69% reduction in BAP and a 61% decrease in WSP from the source inlet to the outlet of the third surface impoundment. A reduction of 37% in BAP and 36% in WSP was observed in the non-dairy watershed. Pathogens were also reduced in downstream impoundments. In the "dairy" watershed reductions of 97% in FC counts, 67% in TC, and 35% in HC counts were observed. Although the non-dairy had 90% lower FC and TC counts and 75% lower HC at the source inlet than observed in the "dairy" watershed, pathogen levels at the outlet were 91% lower in FC, 7% lower in TC, and 51% lower in HC than observed at the source inlet. The study showed that surface impoundments in series can mitigate the impacts of pathogen and nutrient loads from a point source.