Lithologic influences on groundwater recharge through incised glacial till from profile to regional scales: Evidence from glaciated Eastern Nebraska

摘要

Variability in sediment hydraulic properties associated with landscape depositional and\uderosional features can influence groundwater recharge processes by affecting soil-water\udstorage and transmission. This study considers recharge to aquifers underlying river-incised\udglaciated terrain where the distribution of clay-rich till is largely intact in upland locations\udbut has been removed by alluvial erosion in stream valleys. In a stream-dissected glacial\udregion in eastern Nebraska (Great Plains region of the United States), recharge estimates\udwere developed for nested profile, aquifer, and regional scales using unsaturated zone\udprofile measurements (matric potentials, Cl\ud2\udand\ud3\udH), groundwater tracers (CFC-12 and\udSF 6 ), and a remote sensing-assisted water balance model. Results show a consistent\udinfluence of till lithology on recharge rates across nested spatial scales despite substantial\uduncertainty in all recharge estimation methods, suggesting that minimal diffuse recharge\udoccurs through upland glacial till lithology whereas diffuse recharge occurs in river valleys\udwhere till is locally absent. Diffuse recharge is estimated to account for a maximum of 61%\udof total recharge based on comparison of diffuse recharge estimated from the unsaturated\udzone (0–43 mm yr\ud21\ud) and total recharge estimated from groundwater tracers (median 58\udmm yr\ud21\ud) and water balance modeling (median 56 mm yr\ud21\ud). The results underscore the\udimportance of lithologic controls on the distributions of both recharge rates and\udmechanisms.