Location: Northwest Irrigation and Soils Research
Project Number: 2054-13000-009-06-I
Project Type: Interagency Reimbursable Agreement
Start Date: Jul 1, 2018
End Date: Sep 30, 2020
Evaluate the effects of conservation practices in the USR watershed in southern Idaho.
Water samples will continue to be collected weekly during the irrigation season and biweekly during the winter from 10 sites (8 return flow and 2 inflow sites) in the Twin Falls irrigation tract to calculate sediment and nutrient balances for the watershed. Flow rates at these sites will be measured in cooperation with the Idaho Department of Water Resources (IDWR). Return flow data from all sites will be used to calculate annual water, sediment and nutrient balances for the watershed. These balances will be used to determine if the quantity and quality of return flow is changing as more land has converted from furrow to sprinkler irrigation. Additional 500 mL samples will be collected monthly in 2018 from irrigation return flow sites and analyzed for about 20 antibiotics from the following classes: beta-lactam, ionophore, macrolide-lincosamide-streptogramin, tetracycline, and sulfonamide. Samples will be processed and frozen at Kimberly and then sent to the Water Sciences Laboratory at the University of Nebraska-Lincoln for antibiotic residue analysis. Initial qualitative sampling in 2015 with passive samplers detected the antibiotics monensin, oxytetracycline, sulfadimethoxine, sulfamethazine, sulfamethoxazole, trimethoprim, and tylosin. Monthly sampling will identify if consistent spatial and temporal trends in antibiotic detections occur in the irrigation return flow streams. Sediment and nutrient losses will continue to be measured at two sites within a 200 ha subwatershed. Two sites were eliminated in 2018 when sprinkler irrigation was installed on one farm in the subwatershed. The two remaining sites separately measure the water contributed from the sprinkler and furrow irrigated fields within this subwatershed.