Watershed Response to Climate Change and Fire-Burns in the Upper Umatilla River Basin, USA

Abstract

This study analyzed watershed response to climate change and forest fire impacts in the upper Umatilla River Basin (URB), Oregon, using the precipitation runoff modeling system. Ten global climate models using Coupled Intercomparison Project Phase 5 experiments with Representative Concentration Pathways (RCP) 4.5 and 8.5 were used to simulate the effects of climate and fire-burns on runoff behavior throughout the 21st century. We observed the center timing (CT) of flow, seasonal flows, snow water equivalent (SWE) and basin recharge. In the upper URB, hydrologic regime shifts from a snow-rain-dominated to rain-dominated basin. Ensemble mean CT occurs 27 days earlier in RCP 4.5 and 33 days earlier in RCP 8.5, in comparison to historic conditions (1980s) by the end of the 21st century. After forest cover reduction in the 2080s, CT occurs 35 days earlier in RCP 4.5 and 29 days earlier in RCP 8.5. The difference in mean CT after fire-burns may be due to projected changes in the individual climate model. Winter flow is projected to decline after forest cover reduction in the 2080s by 85% and 72% in RCP 4.5 and RCP 8.5, in comparison to 98% change in ensemble mean winter flows in the 2080s before forest cover reduction. The ratio of ensemble mean snow water equivalent to precipitation substantially decreases by 81% and 91% in the 2050s and 2080s before forest cover reduction and a decrease of 90% in RCP 4.5 and 99% in RCP 8.5 in the 2080s after fire-burns. Mean basin recharge is 10% and 14% lower in the 2080s before fire-burns and after fire-burns, and it decreases by 13% in RCP 4.5 and decreases 22% in RCP 8.5 in the 2080s in comparison to historical conditions. Mixed results for recharge after forest cover reduction suggest that an increase may be due to the size of burned areas, decreased canopy interception and less evaporation occurring at the watershed surface, increasing the potential for infiltration. The effects of fire on the watershed system are strongly indicated by a significant increase in winter seasonal flows and a slight reduction in summer flows. Findings from this study may improve adaptive management of water resources, flood control and the effects of fire on a watershed system.

Runoff Modeling of a Coastal Basin to Assess Variations in Response to Shifting Climate and Land Use: Implications for Managed Recharge

“…Monthly and annual NSE values for streamflow calibration (0.878, 0.850) and validation (0.754, 0.627) were within the range of other studies using PRMS, including studies that used automated calibration algorithms (Fang et al 2015;Dams et al 2015;Yazzie and Chang 2017;Ahmadalipour et al 2017). According to these metrics, PRMS reasonably simulated monthly and annual streamflow as well as monthly PET and solar radiation (Figs.…”

Deep aquifer recharge in the Columbia River Basalt Group, upper Umatilla River Basin, northeastern Oregon

“…A PRMS model developed for a 442-mi 2 watershed within the current study area estimated a mean annual recharge over the PRMS model domain of 16.8 in. during 1970-1999(Yazzie and Chang, 2017. This estimate is about 13 percent higher than the estimate for this study when the same area is considered.…”

“…Because many of the components used to calculate recharge are difficult to measure directly or quantify, these estimates contain some uncertainty; however, these uncertainties are not expected to change the overall conclusions of the report. The estimate of recharge due to precipitation shown here, developed using the regression method of Bauer and Vaccaro (1990), compares favorably with an independent estimate of recharge for a relatively large watershed in the study area developed using PRMS by Yazzie and Chang (2017). The use of a process-based model, such as PRMS, for the entire study area could improve recharge estimates by accounting for spatial heterogeneity of land surface characteristics such as soils and land use.…”

Calibration of Precipitation-Runoff Modeling System (PRMS) to simulate prefire and postfire hydrologic response in the upper Rio Hondo Basin, New Mexico

“…Prefire calibrated model results were comparable to other PRMS studies in watersheds that were largely unaffected by fire. Yazzie and Chang (2017) reported calibrated NSE of 0.73 and bias of 3.5 percent in a PRMS study in a forested basin in Oregon. Hay and others (2006) reported calibrated-model NSE ranged from 0.6 to 0.9 in a mountainous 552-mi 2 basin in Colorado.…”

“…Two studies used PRMS to simulate the hydrologic effects of fire but without calibration of the resulting parameters. Konrad (2004) and Yazzie and Chang (2017) determined that the following five parameters should be modified to represent the effects of fire on forest cover by using PRMS: covden_sum, covden_win, rad_trnc, soil_rechr_ max, and soil_moist_max (table 7). Konrad (2004) developed "plausible changes" to these values but did not document the source used to justify the changes or test the resulting postfire model performance after applying these changes.…”