Influence of integrated watershed-scale agricultural conservation practices on lake water quality

Watershed-scale management efforts to improve conservation of water resources in agricultural watersheds depend upon the effectiveness of integrated multiple agricultural best management practices (BMPs). To more comprehensively assess the effectiveness of combined BMPs on water quality requires large-scale, long-term (>10 year) studies measuring key water quality parameters. One such suite of critical water quality parameters includes water clarity, total suspended solids (TSS), and total dissolved solids (TDS). To address this, Beasley Lake, a 25 ha (62 ac) oxbow lake located in a 915 ha (2,261 ac) watershed of intensive row crop agricultural activity, was studied. The lake was sediment impaired when monitoring was initiated in 1995 and was a candidate to assess the effectiveness of watershed-wide BMPs on lake water clarity (as Secchi depth), TSS concentrations, and TDS. A variety of BMPs within row crop fields, at field edges throughout the watershed, and enrollment of 112 ha (277 ac) into the Conservation Reserve Program (CRP) between 1997 to 2006 focused on reducing soil erosion and concomitant sediment runoff. Selected parameters were measured approximately biweekly from 1996 to 2009. During this 14-year period, changes in row crop management and BMP implementations and alterations were observed and recorded in conjunction with targeted water quality parameters. While annual improvement in water quality occurred, distinct seasonal effects were noticeable. Observed changes in water clarity and TSS concentrations were greatest during spring and least in winter in association with increased BMPs, vegetated buffer strips west of the lake, and CRP north of the lake. Observed decreases in TDS concentrations were greatest during summer and fall in association with implemented CRP north of the lake. Reductions in spring TSS by >60% often directly increased spring water clarity by >100%. Results of this study indicate clear improvement in lake water quality with watershed-wide implementation of integrated multiple agricultural BMPs, and these improvements, manifested most strongly during spring, will assist to promote a healthy, sustainable lake ecosystem.