Assessing the impact of vegetative cover within Northeast Arkansas agricultural ditches on sediment and nutrient loads

Ditch systems in Northeast Arkansas drain excess water from Mississippi Delta fields and transport water into larger streams. This conveyance system is part of the larger Mississippi River drainage basin that feeds sediment and nutrients into the Gulf of Mexico. These ditch systems can be an important component of ecosystem services for managing water quality because of their ability to settle sediment and sequester nutrients from field runoff. Vegetation is an important characteristic of these systems that influences sediment and nutrient values. This study investigated the impact of vegetation on water quality in agricultural ditches. Ten sites across two HUC-8 watersheds in Northeast Arkansas were measured weekly for three years to monitor pH, dissolved oxygen, conductivity, flow, turbidity, total suspended solids, total and dissolved nutrients, and chlorophyll a. Bed and bank vegetative coverage were qualitatively characterized at each site. Contaminant loading comparisons report an upstream - downstream increase in loading for all water quality variables, with few exceptions. Sites were then grouped based on vegetation coverage characteristics. Those with greater bed and bank vegetative coverage had reduced loading values compared to sites with less bed and bank coverage across many of the measured parameters. Additionally, many sediment and nutrient parameters were higher in the non-production season compared to the production season despite similar precipitation and discharge across the year, suggesting a need for non-production season control measures. This study helps to understand the important in-stream processes that potentially improve water quality on a regional basis.