UNDERSTANDING AND PREDICTING THE IMPACT OF AGRICULTURE ON THE ENVIRONMENTAL INTEGRITY OF MANAGED WATERSHEDS
Location: Water Quality and Ecology Research
Title: Water quality monitoring of an agricultural watershed lake: the effectiveness of agricultural best management practices
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: June 22, 2011
Publication Date: June 25, 2012
Citation: Lizotte Jr, R.E., Knight, S.S., Locke, M.A., Steinriede Jr, R.W., Testa III, S., Bryant, C.T. 2012. Water quality monitoring of an agricultural watershed lake: the effectiveness of agricultural best management practices. pp. 283-294. In: Hernandez, S., and Brebbia, C.A. (eds.), Design and Nature IV: Comparing Design in Nature with Science and Engineering. WIT Transactions in Ecology and the Environment Series, Volume 160, 332 pp. WIT Press, UK.
Interpretive Summary: We measured water quality in Beasley Lake, a Conservation Evaluation Assessment Program watershed in the Mississippi Delta from 1996 to 2009. Because of farming practices around the lake, water quality was poor when we began the study in 1995. This allowed us to measure the effects of a variety of agriculture best management practices (BMPs) in the watershed on lake water quality. BMPs put in place from 1997-2003 included within-field, edge-of-field, and Conservation Reserve Program (CRP) practices. Water quality was measured every other week and included dissolved solids, suspended solids, nutrients, chlorophyll a, and water clarity. Over the 14 years we studied lake water quality, the lake had less suspended sediments, lower nutrients, and clearer water coinciding with the BMPs put in place and these changes were seen most strongly during spring. Our study showed that BMPs put in place improved lake water quality and will help make a healthy, sustainable lake. These results are of interest to regulatory and other agencies and farming stakeholders by providing additional information to improve and sustain lake and flood plain water quality and overall environmental quality using conservation practices.
Beasley Lake is an oxbow lake located in the Lower Mississippi Alluvial Plain (the Delta), a region of intensive agricultural activity. Due to intensive row-crop agricultural practices, the 915 ha watershed was sediment impaired when monitoring began in 1995 and was a candidate to assess the effectiveness of watershed-wide agricultural best management practices (BMPs) on lake water quality (WQ). BMPs within crop fields, at field edges throughout the watershed, and enrolment of 113 ha into Conservation Reserve Program (CRP) were implemented from 1997-2003 targeting reductions in sediment runoff. Bi-weekly WQ data from 1996-2009 were analyzed. WQ parameters assessed include total dissolved solids (TDS), total suspended solids (TSS), filterable orthophosphate (FOP), total orthophosphate (TOP), total nitrate nitrogen (NO3), total ammonia nitrogen (NH3), chlorophyll a, and water clarity (secchi visibility depth). Over the 14-year period, TSS, TOP, NO3, and NH3 decreased annually whereas chlorophyll a and water clarity increased in conjunction with implemented BMPs. FOP appeared unaffected throughout the monitoring period. While annual improvement in WQ occurred, distinct seasonal effects were noticeable. Changes in TSS, TOP, NO3, NH3, and water clarity were greatest during spring and negligible in winter. Changes in TDS were observed only during summer. Reductions in spring TSS directly reduced TOP, increased chlorophyll a and water clarity. Results of this study indicate clear improvement in Mississippi Delta lake WQ with watershed-wide implementation of agricultural BMPs and these improvements, manifested most strongly during spring, will promote a healthy, sustainable lake ecosystem.