Selenium in waters in and adjacent to the Kendrick Project, Natrona County, Wyoming

Abstract

Introduction ___ Problem _-Purpose and scope of the investigation Location and extent of the area Previous investigations Well-numbering system Acknowlegments _-Present development and water use Selenium _________ _ Method of investigation _ _ Selenium in rocks ________-_-Eocks of pre-Cretaceous age 10 Rocks of Cretaceous age 10 Rocks of Tertiary age __ _ _ 11 Rocks of Quaternary age Distribution of selenium in rocks ____ 11 Selenium in water ________ _ ____ __________ _ Ground water ____ _ _ _ _____ _-__________ Groundwater sampling _________________________ Surface water _________ ______ _______________ 29 Surface-water sampling _______________________ 29 Mass water sampling _____ _ ___ ____________ 35 Summary and conclusions _________________________ References cited _______________________________ 38 2 NATRONA COUNTY, WYOMING Poison Spring Creek, Poison Spider Creek, Oregon Trail Drain, and Casper Creek are the principal tributaries that contribute selenium to the North Platte River. The selenium load, expressed in pounds per day, in Poison Spring Creek and Poison Spider Creek decreased slightly during the first year of sampling and increased slightly during the second year of sampling. The selenium load in Oregon Trail Drain is greatest in late winter and early spring during the period of low flow; the se^nium load in Casper Creek varies, but shows no correlation with season ard little correlation with stream discharge. The North Platte River above and below the irrigation project had consistently low selenium concentrations, 10/ig/l (micrograms per liter) or less, in the period April 1968 through June 1969. The total selenium load contributed to the North Platte River from tributaries in the study area is almost undetectable after mixing with the river water. From the fall of 1968 to the spring of 1969, results of water srmpling in areas influenced by irrigation show that the selenium concentration increased at 29 percent of the locations (average net increase of 64C Mg/1), decreased at 34 percent of the locations (average net decrease of 80/ug/l), and had little (10 /tg/1 or less) or no change at 37 percent of the locations. As a comparison, results of water sampling in areas not influer^ed by irrigation showed that the selenium concentration increased at 2 percent of the locations (average net increase of 30 Mg/1), decreased at 26 percent of the locations (average net decrease of 30,ug/l), and had 1'ttle or no change at 72 percent of the locations. It is not possible to make a general statement that would be applicable to the entire Kendrick Project concerning the effects of irrigation on the selenium concentration in waters of the area; however, irrigation undoubtedly has accelerated movement of selenium within and from the irrigated areas.