Global Sensitivity of Simulated Water Balance Indicators Under Future Climate Change in the Colorado Basin

Abstract

The Colorado River Basin is a fundamentally important river for society, ecology, and energy in the United States. Streamflow estimates are often provided using modeling tools which rely on uncertain parameters; sensitivity analysis can help determine which parameters impact model results. Despite the fact that simulated flows respond to changing climate and vegetation in the basin, parameter sensitivity of the simulations under climate change has rarely been considered. In this study, we conduct a global sensitivity analysis to relate changes in runoff, evapotranspiration, snow water equivalent, and soil moisture to model parameters in the Variable Infiltration Capacity (VIC) hydrologic model. We combine global sensitivity analysis with a space‐filling Latin Hypercube Sampling of the model parameter space and statistical emulation of the VIC model to examine sensitivities to uncertainties in 46 model parameters following a variance‐based approach. We find that snow‐dominated regions are much more sensitive to uncertainties in VIC parameters. Although baseflow and runoff changes respond to parameters used in previous sensitivity studies, we discover new key parameter sensitivities. For instance, changes in runoff and evapotranspiration are sensitive to albedo, while changes in snow water equivalent are sensitive to canopy fraction and Leaf Area Index (LAI) in the VIC model. It is critical for improved modeling to narrow uncertainty in these parameters through improved observations and field studies. This is important because LAI and albedo are anticipated to change under future climate and narrowing uncertainty is paramount to advance our application of models such as VIC for water resource management.

Sensitivity Analysis‐Based Automatic Parameter Calibration of the VIC Model for Streamflow Simulations Over China

“…The K parameter is the hydraulic conductivity when the soil moisture reaches saturation (Yang et al, 2014). The finding that streamflow is not sensitive to the K parameter is consistent with previous studies (Bennett et al, 2018;Demaria et al, 2007).…”

“…For example, only 13 streamflow‐related soil parameter were involved in sensitivity analysis and optimization, and the effects of the vegetation parameters (e.g., LAI, albedo, roughness length, and canopy fraction) are not taken into account in this study. Previous studies have indicated that changes in runoff are sensitive to albedo (Bennett et at., ) and vegetation roots (Demaria et al, ) in the VIC model. Therefore, the optimal solution found by our automatic calibration framework is likely to be compensating for errors in some of the other vegetation parameters and model prediction uncertainty sources, including input data and structural uncertainties associated with the underlying model.…”

“…The variable infiltration capacity (VIC) model was developed as a physically based distributed macroscale hydrological model by Liang et al (1994), and it has been widely used in streamflow simulations around the world, including China (Zhang et al, 2014), the United States (Niraula et al, 2017), Europe (Greuell et al, 2018), India (Chawla & Mujumdar, 2018), and other regions. VIC is able to capture transient basin discharge and has 46 or more tunable parameters (Bennett et al, 2018). Although we know that parameter sensitivities respond to the dynamic environment in a basin and automatic calibration performs better than manual calibration, the practice of manually calibrating the seven expert-recommended parameters (hereinafter referred to as the seven default parameters) is still largely used in VIC model calibration (Niraula et al, 2017;Ran et al, 2017;Wang et al, 2018;Xie et al, 2007;Zhang et al, 2014).…”

Sensitivity analysis and uncertainty assessment in water budgets simulated by the variable infiltration capacity model for Canadian subarctic watersheds

“…The sensitivity of model outputs to selected parameters is justified given the formulations of the variable infiltration and baseflow generation curve that form the foundation of the VIC architecture (Liang et al, , ) and as these parameters are traditionally applied in model calibration (i.e., Elsner et al, ). As reported in previous studies, sensitivity to these parameters hold in both current and future climate scenarios (Bennett et al, ; Christensen & Lettenmaier, ; Demaria et al, ). A previous effort used various objective functions and found that b inf and D2 were the most sensitive parameters followed by the drainage parameter among 10 VIC parameters across four American river basins of different hydroclimates (Demaria et al, ).…”

Threats to a Colorado river provisioning basin under coupled future climate and societal scenarios

“…Projected changes to natural systems, particularly from climate, include shifts in temperature distributions, changes in the timing of streamflow extremes, and intensifying drought [11,12]. All of these impacts have significant consequences for large, managed river systems such as the Colorado River Basin (CRB).…”