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Title: Surface impoundments effectiveness for fecal bacteria and nutrient mitigation

Author
item Daniel, John
item ELMENDORF, DAVID - UNIV. CENTRAL OKLA.
item MADDOX, SCOTT - UNIV. CENTRAL OKLA.

Submitted to: ASAE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: 7/15/2004
Publication Date: 8/1/2004
Citation: Daniel, J.A., Elmendorf, D., Maddox, S. 2004. Surface impoundments effectiveness for fecal bacteria and nutrient mitigation. Proceedins of American Society of Agricultural Engineers Annual International Meeting, August 1-4, 2004, Ottawa, Ontario, Canada. Paper No. 042137. 2004 CD-ROM.

Interpretive Summary: Public concern over agriculture's impact on water quality has prompted the formulation of economic, yet effective methods to reduce nutrient movement in surface water and prevent environmental damage. This study monitored the change in nutrient and pathogen levels to determine the effectiveness of stockponds for enhancing downstream water quality. A three year study was conducted to evaluate water quality of an agricultural watershed with a small (350 head) dairy operation. Two livestock ponds on the downstream drainage were sampled monthly and analyzed for nutrients and pathogens. An upstream dairy source was also sampled. Nutrients included nitrate-N, bioavailable phosphorus (BAP) and water soluble phosphorus (WSP) and organisms monitored were fecal (FC) and total coliforms (TC) and heterogenic bacteria counts (HC). A decrease in nutrients and pathogen levels were found in the water samples throughout the watershed including between the grassed channel which lies between the source sampling site and the stockpond inlet. Nitrate-N levels were <1 mg/L and remained low. Below the second impoundment, BAP and WSP were reduced to 10% and 20% of the source, respectively, while FC was <1%, TC was 1% and HC was 40% of the source. Common conservation practices, such as stock ponds and grassed channels, appear to be effective for enhancing downstream water quality and economically removing nutrients and pathogens.

Technical Abstract: A small, multiple land use watershed (1000 ha) was studied over a three year period to provide insight on nutrient and pathogen levels associated with conventional winter wheat and native rangeland grazing practices and the effluent contributions from a small (350 head) dairy operation, and to determine the effectiveness of successive surface impoundments for reducing the impact of effluents. This watershed incorporates a variety of management practices including grazed winter wheat pastures and native rangeland. Two surface impoundments positioned sequentially on the watershed drainage were sampled. Monthly water samples were collected from each surface impoundment as well as a location 0.5 km upstream from the first impoundment (i.e., source inlet). Inlet and outlet samples from the impoundments were collected. The samples were analyzed for nitrate-nitrogen (NO3-N), water-soluble phosphorus (WSP), bioavailable phosphorus (BAP), fecal and total coliforms (FC and TC), and heterotrophic bacteria (HC). A decrease in nutrients and pathogen concentrations was found in impoundment water samples throughout the watershed drainage, including the grassed drainage between the source sampling site and the inlet of the first impoundment. Nitrate-N levels were found to decrease even though the levels were initially low (<1 mg/L). The sequentially-placed impoundments further mitigated the surface runoff and reduces the nutrient and pathogen levels. BAP and WSP were reduced to levels 10% and 20% of the source, respectively, while FC was at <1%, TC was 1% and HC was 40% of the source. The grass channels and surface impoundments seem be an economic and effective conservation practice to enhance surface water quality.