Location: Sustainable Water Management Research
Title: Seasonal water quality trends in a tailwater recovery system in the Mississippi DeltaAuthor
Nelson, Amanda | |
Witthaus, Lindsey | |
Moore, Matthew | |
Griffith, Mark | |
Locke, Martin | |
Taylor, Jason | |
Lizotte, Richard |
Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 9/9/2022 Publication Date: 1/1/2023 Citation: Nelson, A.M., Witthaus, L.M., Moore, M.T., Griffith, M.K., Locke, M.A., Taylor, J.M., Lizotte Jr, R.E. 2023. Seasonal water quality trends in a tailwater recovery system in the Mississippi Delta. Agricultural Water Management. 78(1):26-32. https://doi.org/10.2489/jswc.2023.00090. DOI: https://doi.org/10.2489/jswc.2023.00090 Interpretive Summary: Tailwater recovery (TWR) systems are an important best management practice (BMP) used to address both water quality and quantity issues in the Mississippi Delta region. TWRs are systems for capturing surface water runoff to be later used for irrigation. TWRs consist of a ditch to capture runoff; an on-farm storage (OFS) reservoir to store captured water; and pumps to move surface water from the ditch into the OFS reservoir and to irrigate nearby fields. To determine if TWR systems are an effective way to reduce downstream nutrient loads, water quality and quantity data from a ditch and pond TWR system in Sunflower County, MS, were measured for five years. The objectives of this study were to assess seasonal TWR system runoff and runoff water quality trends. All water quality parameters had clear seasonal variation, except for chlorophyll a. Dissolved oxygen, solids, total dissolved organic carbon, total phosphorus, and total Kjeldahl nitrogen exhibited significant differences between OFS reservoir and ditch sites. Total solids were 2 to 4 times higher in the ditch than in the reservoir, depending on the season, indicating sediment lost from fields through surface runoff is not necessarily being returned to the fields via irrigation from the reservoir as is sometimes listed as a potential benefit of TWRs. Nutrients were also generally higher in the ditch than the reservoir. These results suggest the reservoir serves an important function to process nutrients and sediments through settling, biological uptake of nutrients, and biogeochemical transformations. This emphasizes the importance of either a closed TWR system or creating an outflow for the system from the reservoir rather than the ditch. Technical Abstract: In the Mississippi Delta region, tailwater recovery (TWR) systems are an important best management practice (BMP) used to address both water quality and quantity issues. TWRs are surface water capture-and-irrigation reuse systems using a combination of a ditch to capture surface water; an on-farm storage (OFS) reservoir to store captured surface water; and pumps to move surface water from the ditch into the OFS reservoir and to irrigate nearby fields. To determine if TWR systems are an effective way to reduce water use and downstream nutrient loads, water quality and quantity data from a ditch and pond TWR system in Sunflower County, MS, were measured for five years. Objectives of this study were to assess seasonal TWR system runoff and runoff water quality trends. All water quality parameters had clear seasonal variation, except for chlorophyll a. Dissolved oxygen, solids, conductivity, total dissolved organic carbon, total phosphorus, and total Kjeldahl nitrogen exhibited significant differences between OFS reservoir and ditch sites. Total solids were 2 to 4 times higher in the ditch than in the reservoir, depending on the season, indicating sediment lost from fields through runoff is not necessarily being returned to the fields via irrigation from the reservoir as is sometimes listed as a potential benefit of TWRs. Nutrients were also generally higher in the ditch than the reservoir. Phosphate was 1.4 times higher in the ditch in spring compared to the reservoir, while ammonium and nitrate were two to four times higher in the ditch during the summer. These results suggest the reservoir serves an important function to process nutrients and sediments through settling, biological uptake of nutrients, and biogeochemical transformations and emphasizes the importance of a closed TWR system. |