Comparison of CMIP3 and CMIP5 projected hydrologic conditions over the Upper Colorado River Basin

Abstract

This work presents updated hydrologic projections for the Upper Colorado River Basin (UCRB) using downscaled (approximately 12 km) General Circulation Model (GCM) output from Coupled Model Intercomparison Project – Phase 5 (CMIP5) with a comparison to CMIP3 GCMs. We use the Soil and Water Assessment Tool model to simulate the impacts of end‐of‐century climate change on the UCRB using 21 CMIP5 and 18 CMIP3 GCMs, collected into one CMIP5 ensemble and one CMIP3 ensemble, respectively. Previous CMIP3 studies have identified a drier climate for the UCRB because of projected increases in temperature and decreases/little change in precipitation. Hydrologic simulations from CMIP5 inputs suggest wetter conditions than simulations based on CMIP3 inputs, yet drier conditions than the historical climate. Both ensembles lead to timing shifts in peak streamflow during the snowmelt season from changes in snowmelt, but the higher CMIP5 projected precipitation leads to, on average, peak streamflows 200–300 m3 s−1 larger (25–40% difference) than the CMIP3 projections. This difference is largely generated in the northern UCRB region, where CMIP5 simulations project much more significant increases in streamflow than CMIP3. This increase is largely due to an overall larger rise in precipitation in the CMIP5 ensemble (57% of the total UCRB area) compared to the CMIP3 ensemble (5%). Even with projected increases in precipitation, snowmelt is projected to decrease dramatically throughout the UCRB for both ensembles. The increases in precipitation and decreases in snowmelt leads to significant differences in hydrologic flux components between the CMIP3 and CMIP5 ensembles, such as end‐of‐century rises in soil water content and evapotranspiration in the CMIP5 ensemble compared to the CMIP3 ensemble. The difference between the dry CMIP3 and the somewhat wetter CMIP5 projections may be critical for water management in the already over‐allocated UCRB.

Multiple Climate Change Scenarios and Runoff Response in Biliu River

“…Moreover, the temperature increases more under CMIP5 than under CMIP3 scenarios. Several studies have shown that CMIP5 presents warmer and wetter predictions [19,20]. Meanwhile, the ranges of change in both precipitation and runoff under CMIP5 are much wider than under CMIP3, which indicates that the selected CMIP5 scenarios are more effective in capturing future runoff uncertainties than the selected CMIP3 scenarios.…”

“…Several studies have revealed that, compared to CMIP3, CMIP5 ensemble simulations have substantially improved the statistical representation of daily mean precipitation and temperature [17,18]. However, few studies have compared the impacts of CMIP3 and CMIP5 on the design of the planning and management infrastructure of water resources [19][20][21], especially in China [22].…”

“…However, the design of the water transfer project was based on CMIP3 data, which may inaccurately estimate the severity of a water resource shortage [19,20]. Therefore, it is necessary to compare the availability of simulated water resources using CMIP3 and CMIP5, which can provide important information on the differences in the availability of projected water resources and therefore facilitate the design and evaluation of the water transfer project [19][20][21].…”

Changing station coverage impacts temperature trends in the Upper Colorado River basin

“…Climate projections suggest that temperatures will rise across the Colorado River basin, although precipitation changes are uncertain (e.g., Seager et al, ; Ayers et al, ). These projected changes, combined with frequent, protracted drought, have enhanced the scientific and management communities’ interest in understanding the ways in which major river systems like the Colorado River respond to climatic fluctuations, particularly those that are not uniform across the basin (see Woodhouse et al, ), such as elevation‐dependent warming (Mountain Research Initiative EDW Working Group, ).…”

“…Specifically, increases in the number of highelevation stations in the UCRB may have led to an underestimation of elevationdependent warming, particularly during the spring. This phenomenon is unlikely limited to this specific basin and may be present in other high-elevation watersheds across the western United States K E Y W O R D S climate trends, Colorado River, elevation-dependent warming, gridded data, temperature 1 | INTRODUCTION Climate projections suggest that temperatures will rise across the Colorado River basin, although precipitation changes are uncertain (e.g., Seager et al, 2013;Ayers et al, 2016). These projected changes, combined with frequent, protracted drought, have enhanced the scientific and management communities' interest in understanding the ways in which major river systems like the Colorado River respond to climatic fluctuations, particularly those that are not uniform across the basin (see Woodhouse et al, 2016), such as elevation-dependent warming (Mountain Research Initiative EDW Working Group, 2015).…”