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Journal of Environmental Hydrology
ISSN 1058-3912 |
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Electronic Journal of the International Association for
Environmental Hydrology
JEH Volume 17 (2009), Paper 26 Posted October 19, 2009 EVALUATION OF SELENIUM LOADING TO THE ARKANSAS RIVER NEAR PUEBLO, COLORADO
Craig E. Divine1 2Civil and Environmental Engineering Department, Colorado State University, Colorado, USA 3City of Pueblo Water Reclamation Facility, City of Pueblo, Colorado, USA ABSTRACT A focused investigation was conducted on a 40-km reach of the Arkansas River in the vicinity of Pueblo, Colorado, to quantify the effect on selenium (Se) load of irrigation return flows compared to return flows from other sources. Results show that two tributaries that are minimally influenced by irrigated agriculture contributed the largest Se loads: 22% by Wild Horse Creek and 21% by Fountain Creek. Water quality, geology, and land use data suggest that the highest Se concentrations in groundwater are a result of natural dissolution processes from the underlying shale bedrock and shale residuum, and that Se concentrations in irrigated alluvial zones are not meaningfully higher than those in the non-irrigated alluvium. Within the study area, irrigation practices do not substantially increase Se concentrations in shallow groundwater. They do, howver, increase total water and Se flux. The Se load from groundwater discharge and agricultural return flow estimated by three methods is likely between about 0.01 to 0.05 kg day-1 per km, which is small relative to the total average Se load through the study reach (0.2 kg day-1 per km). A simple mass balance Se load model was developed and the results indicate that only about 10 to 20 percent of the total Se source loads are derived from return flow from irrigated land. This study highlights the potential significance of natural and other Se sources relative to enhanced dissolution caused by irrigated agriculture, particularly in areas underlain by shale bedrock. Reference: Divine, C.E., T.K. Gates, N. Keller, and G.Y. Michael. 2009. Evaluation of Selenium Loading to the Arkansas River Near Pueblo, Colorado. Journal of Environmental Hydrology, Vol. 17, Paper 26. CONTACT: Craig E. Divine ARCADIS U.S. 630 Plaza Drive, #100 Highlands Ranch, Colorado 80129 USA E-mail: craig.divine@arcadis-us.com |
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