Assessment of runoff water quality for an integrated best-management practice system in an agricultural watershed

Authors: Lizotte, Richard; Locke, Martin

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/2017
Publication Date: 5/15/2018
Citation: Lizotte Jr, R.E., Locke, M.A. 2018. Assessment of runoff water quality for an integrated best-management practice system in an agricultural watershed. Journal of Soil and Water Conservation. 73(3):245-254.

Interpretive Summary: As we improve our understanding of how best to use combined agricultural best management practices (BMPs) to reduce suspended solids and nutrient loads and improve water quality, an improved understanding of combined BMP effectiveness is needed. To do this, we collected runoff measurements of total suspended solids, total phosphorus, ortho-phosphate phosphorus, total nitrogen, ammonium, and nitrate draining through vegetated drainage ditches into a vegetated sediment pond from crop-cultivated areas as part of the Conservation Evaluation Assessment Program watershed in the Mississippi Delta from 2011 to 2014. We observed how vegetated drainage ditches combined with a vegetated sediment pond were effective in reducing suspended solids loads and moderately effective at reducing total phosphorus and total nitrogen loads in runoff. Our study showed that vegetated drainage ditches with vegetated sediment pond BMPs put in place reduced suspended solids and total nutrient loads and improved runoff water quality. Our results are of interest to regulatory and other agencies and farming stakeholders by providing additional information to improve and sustain water quality and overall environmental quality using combined conservation practices.

Technical Abstract: To better understand, implement and integrate best management practices (BMPs) in agricultural watersheds, critical information on their effectiveness is required. A representative agricultural watershed, Beasley Lake, was used to compare runoff water quality draining through an integrated system of BMPs from row-crop cultivated sub-drainages as part of the national Conservation Effects Assessment Program (CEAP). From 2011-2014, runoff samples were collected across 3 sub-drainages representing two integrated BMPs and 3 sub-drainages representing row-crop cultivation. Best management practice sites studied were two (east and west) vegetated drainage ditches (EDV, WDV) that subsequently flowed into a vegetated sedimentation pond (SP). A suite of critical water quality parameters were assessed and included total suspended solids (TSS), total phosphorus (TP), total nitrogen (TN), nitrate-nitrogen (NO3-N), ammonium-nitrogen (NH4-N), and orthophosphate-phosphorus (PO4-P). During the 4-year study period, integrated BMPs were effective at mitigating TSS runoff loads relative to row-crop but less effective at mitigating nutrient runoff loads. Runoff from WDV and SP were only moderately effective in mitigating nutrients in runoff with only TN and TP consistently reduced relative to row-crop. Effectiveness of BMPs was primarily a result of the amount of acreage in tillage practices and crops planted relative to BMP within sub-drainage basin acreage. Decreasing tillage:BMP and/or crop:BMP area ratios produced a subsequent decrease in runoff loads with the exception of NH4-N and PO4-P.