Stable isotopic composition of precipitation in the semi-arid north-central portion of the US Great Plains

Where data are available, hydrologic studies may use stable oxygen and hydrogen isotopes to investigate, groundwater/ surface water interaction, groundwater recharge and advective/diffusive transport, to estimate groundwater ages or to unravel paleohydrology. Such studies require that the isotopic composition of precipitation be known, as precipitation is a major input to groundwater and surface water systems. Oxygen-18 (delta O-18) and deuterium (delta H-2) data for precipitation are lacking for the semi-arid portion of the north-central Great Plains of the US, and thus there is need to establish additional meteoric water lines as isotope input functions across the region, as well as to develop better understanding of the isotopic climate linkages that control oxygen and hydrogen isotope ratios in precipitation. This study examines the delta O-18 and delta H-2 composition of precipitation for a representative site near North Platte, Nebraska in the semi-arid north-central Great Plains during the years 1989 through 1994. Oxygen-18 values range from -30.5 to +1.7 parts per thousand. Deuterium values range from -228 to +11 parts per thousand. Yearly arithmetic mean values for the North Platte station are -9.8 and -71 parts per thousand, respectively. Weighted yearly means for delta O-18 and delta H-2 over the 6-year period were -9.6 and - 69 parts per thousand, respectively. North Platte values show a strong isotopic enrichment between winter and summer precipitation, and a strong delta O-18-T correlation r(2) = 0.845 for mean monthly values of 0.54 parts per thousand per degree Celsius. The local meteoric water line for the site is delta H-2 = 7.66 delta O-18 + 4.96. (C) 2000 Elsevier Science B.V. All rights reserved.