A numerical investigation of bedrock groundwater recharge and exfiltration on soil mantled hillslopes

W. Payton Gardner, Kelsey Jensco, Zachary H. Hoylman, Robert Livesay, Marco P. Maneta

Research output: Contribution to journalArticlepeer-review

Abstract

Here we use Richards Equation models of variably saturated soil and bedrock groundwater flow to investigate first-order patterns of the coupling between soil and bedrock flow systems. We utilize a Monte Carlo sensitivity analysis to identify important hillslope parameters controlling bedrock recharge and then model the transient response of bedrock and soil flow to seasonal precipitation. Our results suggest that hillslopes can be divided into three conceptual zones of groundwater interaction, (a) the zone of lateral unsaturated soil moisture accumulation (upper portion of hillslope), (b) the zone of soil saturation and bedrock recharge (middle of hillslope) and (c) the zone of saturated-soil lateral flow and bedrock groundwater exfiltration (bottom of hillslope). Zones of groundwater interaction expand upslope during periods of precipitation and drain downslope during dry periods. The amount of water partitioned to the bedrock groundwater system a can be predicted by the ratio of bedrock to soil saturated hydraulic conductivity across a variety of hillslope configurations. Our modelled processes are qualitatively consistent with observations of shallow subsurface saturation and groundwater fluctuation on hillslopes studied in our two experimental watersheds and support a conceptual model of tightly coupled shallow and deep subsurface circulation where groundwater recharge and discharge continuously stores and releases water from longer residence time storage.

Original languageEnglish
Pages (from-to)3311-3330
Number of pages20
JournalHydrological Processes
Volume34
Issue number15
DOIs
StatePublished - Jul 15 2020

Keywords

  • aquifer recharge
  • mountain block aquifer
  • soil moisture
  • streamflow generation
  • watershed storage

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