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United States Department of Agriculture

Agricultural Research Service

Research Project: UNDERSTANDING AND PREDICTING THE IMPACT OF AGRICULTURE ON THE ENVIRONMENTAL INTEGRITY OF MANAGED WATERSHEDS Title: The limnology of a Mississippi River alluvial plain oxbow lake following the application of conservation practices

item Knight, Scott
item Cullum, Robert
item Lizotte, Richard

Submitted to: Journal of Water Resource and Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 2014
Publication Date: N/A

Interpretive Summary: A long term study was conducted to test the effectiveness of conservation practices in reducing sediment and nutrient entering an oxbow lake via agricultural runoff. The study showed that conservation practices such as reduced tillage, grass buffers and CRP caused sediment concentrations to decrease and water clarity and plankton to increase over time improving the water quality of the lake. Additionally, nutrients from fertilizers, such as phosphorus and nitrogen significantly decreased from 1995 through 2011. The amount of plankton was also shown to be dependent upon the amount of nitrogen in the water. This research demonstrates the effectiveness of watershed based conservation practices in reducing sediment and nutrients, increasing water clarity and boosting primary production as indicated by chlorophyll a. Further it provides insight into the interactions of water quality features within shallow oxbow lakes.

Technical Abstract: From 1995 and 2011 Beasley Lake watershed near Indianola, MS, was subjected to a variety of conservation measures designed to reduce water velocity, erosion and discharge of sediment laden water. Water quality monitoring during the period indicated a number of long term trends and relationships between the parameters measured. Conservation practices reduced sediments and nutrients during the course of the study that resulted in increased Secchi visibility and chlorophyll a. Annual mean dissolved oxygen decreased slightly over time and was strongly dependent upon temperature, and weakly associated with varying salinity and pH. Total phosphorus, ammonium nitrogen and nitrate nitrogen showed significant downward trends from 1995 through 2011. Chlorophyll a concentration was significantly dependent upon total nitrogen but not phosphate, indicating nitrogen limiting conditions. Watershed based conservation practices significantly changed the long term water quality of Beasley Lake by reducing sediment and nutrients, increasing water clarity and boosting primary production as indicated by chlorophyll a.

Last Modified: 7/4/2015
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