Preprints
https://doi.org/10.5194/hess-2020-558
https://doi.org/10.5194/hess-2020-558

  21 Jan 2021

21 Jan 2021

Review status: this preprint is currently under review for the journal HESS.

Combined Impacts of Uncertainty in Precipitation and Air Temperature on Simulated Mountain System Recharge from an Integrated Hydrologic Model

Adam P. Schreiner-McGraw and Hoori Ajami Adam P. Schreiner-McGraw and Hoori Ajami
  • Department of Environmental Sciences, University of California, Riverside, 92521, USA

Abstract. Mountainous regions act as the water towers of the world by producing streamflow and groundwater recharge, a function that is particularly important in semiarid regions. Quantifying rates of mountain system recharge is difficult, and hydrologic models offer a method to estimate recharge over large scales. These recharge estimates are prone to uncertainty from various sources including model structure and parameters. The quality of meteorological forcing datasets, particularly in mountainous regions, is a large source of uncertainty that is often neglected in groundwater investigations. In this contribution, we quantify the impact of uncertainty in both precipitation and air temperature forcing datasets on the simulated groundwater recharge in the mountainous watershed of the Kaweah River in California, USA. We make use of the integrated surface water – groundwater model, ParFlow.CLM and several gridded datasets commonly used in hydrologic studies, downscaled NLDAS-2, PRISM, Daymet, Gridmet, and TopoWx. Simulations indicate that across all forcing datasets, mountain front recharge is an important component of the water budget in the mountainous watershed accounting for 25–46 % of the annual precipitation, and ~90 % of the total mountain system recharge to the adjacent Central Valley aquifer. The uncertainty in gridded air temperature or precipitation datasets, when assessed individually, results in similar ranges of uncertainty in the simulated water budget. Variations in simulated recharge to changes in precipitation (elasticities) and air temperature (sensitivities) are larger than 1 % change in recharge per 1 % change in precipitation or 1-degree C change in temperature. The total volume of snowmelt is the primary factor creating the high water budget sensitivity; and snowmelt volume is influenced by both precipitation and air temperature forcings. The combined effect of uncertainty in air temperature and precipitation on recharge is additive, and results in uncertainty levels roughly equal to the sum of the individual uncertainties. Mountain system recharge pathways including mountain block recharge, mountain aquifer recharge, and mountain front recharge are less sensitive to changes in air temperature than changes in precipitation. Mountain front and mountain block recharge are more sensitive to changes in precipitation than other recharge pathways. The magnitude of uncertainty in the simulated water budget reflects the importance of developing high qualify meteorological forcing datasets in mountainous regions.

Adam P. Schreiner-McGraw and Hoori Ajami

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2020-558', Anonymous Referee #1, 29 Mar 2021
  • RC2: 'Comment on hess-2020-558', Anonymous Referee #2, 12 Apr 2021

Adam P. Schreiner-McGraw and Hoori Ajami

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Combined Impacts of Uncertainty in Precipitation and Air Temperature on Simulated Mountain System Recharge from an Integrated Hydrologic Model Adam P. Schreiner-McGraw and Hoori Ajami https://datadryad.org/stash/share/IM0AcvOHM4NOjgLsuq647Y2oWJqzbDULUos6_gpWIO0

Adam P. Schreiner-McGraw and Hoori Ajami

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Short summary
We assess the impact of uncertainty in measurements of precipitation and air temperature on simulated groundwater processes in a mountainous watershed. We illustrate the role of topography in controlling how uncertainty in the input datasets propagates through the soil and into the groundwater. While the focus of previous investigations has been on the impact of precipitation uncertainty, we show that air temperature uncertainty is equally important in controlling the groundwater recharge.