Isotopic investigation of recharge to a regional groundwater flow system, Great Basin, NV

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Groundwater recharge processes were investigated in central Nevada by examining the relationships between the stable isotope ({delta}D and {delta}{sup 18}O) compositions of snowfall, snowmelt, alpine spring waters, and regional groundwaters. Snowmelt infiltration is inferred to he the dominant source of groundwater recharge in this region. Bulk snow cores collected throughout central Nevada near the time of maximum accumulation have {delta}D and {delta}{sup 18}O pairs that plot subparallel to the global meteoric water line (GMWL), but have negative d-values, implying kinetic isotope enrichments. Heavy isotope enrichments occur at the base of snowpacks due to fractionation during snow metamorphism, sometimes resulting in ... continued below

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Criss, R E; Davisson, M L; Rose, T & Smith, D K May 4, 1999.

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Groundwater recharge processes were investigated in central Nevada by examining the relationships between the stable isotope ({delta}D and {delta}{sup 18}O) compositions of snowfall, snowmelt, alpine spring waters, and regional groundwaters. Snowmelt infiltration is inferred to he the dominant source of groundwater recharge in this region. Bulk snow cores collected throughout central Nevada near the time of maximum accumulation have {delta}D and {delta}{sup 18}O pairs that plot subparallel to the global meteoric water line (GMWL), but have negative d-values, implying kinetic isotope enrichments. Heavy isotope enrichments occur at the base of snowpacks due to fractionation during snow metamorphism, sometimes resulting in remarkably systematic isotopic variations. Ice crystals in the soil immediately beneath the snowpack can be strongly depleted in heavy isotopes relative to the overlying snow, implying fractionation or exchange with the snowpack. Late season ablation processes tend to homogenize isotopic variations between snowpack layers, and cause the bulk isotopic composition of the snowpack to become enriched in {sup 18}O by 2-3{per_thousand} relative to the composition during peak accumulation. The dynamic evolution of the snowpack and snowmelt isotopic compositions over time makes it difficult to directly ascertain groundwater recharge compositions without careful mass balance measurements. Preliminary evidence suggests that small local springs may be reasonable indicators of the integrated isotopic value of the snowmelt recharge in a particular area. Springs and snowmelt runoff samples collected throughout central Nevada during the peak runoff plot along a least squares regression line with the equation {delta}D = 7.3{delta}{sup 18}O - 7, which is similar to the line obtained for 28 metamorphosed snow cores collected during peak accumulation ({delta}D = 7.5{delta}{sup 18}O - 3). These results suggest that kinetic fractionation processes during snow metamorphism and ablation may largely account for the low d-values that are widely observed in groundwaters from both local and regional flow systems in Nevada.

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1.1 Megabytes pages

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  • International Symposium on Isotope Techniques in Water Resources Development and Management, Vienna (AT), 05/10/1999--05/14/1999

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  • Report No.: UCRL-JC-132514
  • Grant Number: W-7405-ENG-48
  • Office of Scientific & Technical Information Report Number: 14135
  • Archival Resource Key: ark:/67531/metadc623298

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  • May 4, 1999

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  • June 16, 2015, 7:43 a.m.

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  • May 6, 2016, 1:31 p.m.

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Criss, R E; Davisson, M L; Rose, T & Smith, D K. Isotopic investigation of recharge to a regional groundwater flow system, Great Basin, NV, article, May 4, 1999; California. (digital.library.unt.edu/ark:/67531/metadc623298/: accessed September 26, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.