Assessing best management practices for remediation of selenium loading in groundwater to streams in an irrigated region

- Selenium remediation strategies in a river valley aquifer system are explored.
- Numerical model simulating Se and N fate and transport in groundwater is used.
- Effect of reduced irrigation, canal sealing, and land fallowing explored.
- Effect of reduced fertilizer loading, enhanced riparian buffer zones explored.
- Model shows significant improvement in Se contamination from baseline.

SummarySelenium (Se) contamination in groundwater and surface water in numerous river basins worldwide has become a critical issue in recent decades. An essential micro-nutrient, Se can prove harmful to fish, water fowl, livestock, and even humans at elevated concentrations. In an overall effort to curb Se contamination in environmental systems, this study aims to identify best-management practices (BMPs) that can assist in remediating Se contamination in irrigated river basins. Using multi-decadal simulations of a calibrated and tested groundwater flow model (MODFLOW-UZF) and Se chemical reactive transport model (UZF-RT3D), the impact of water- and land-management strategies in reducing Se contamination are explored for a 500 km2 study region in the Lower Arkansas River Valley (LARV) in southeastern Colorado. The effectiveness of reduced applied irrigation volumes, sealing of earthen irrigation canals, rotational fallowing of cultivated land, reduced fertilizer loading, and enhanced riparian buffer zones, implemented individually as well as concurrently in various combinations, is explored. Results indicate that significant (>10%) decreases in Se mass loading to the Arkansas River system (main stem and tributaries) can be achieved when individual BMPs are implemented, with land fallowing, reduced irrigation, and enhanced riparian buffer zones providing the best results (13-14% load reduction). Even greater impacts (20-50% Se load reduction) can be achieved with 3 or 4 BMPs implemented concurrently. Results demonstrate that Se remediation can potentially be achieved within the LARV, and also can serve as a guide for other Se-affected river basins within the western United States and throughout the world.