Abstract
Future streamflow in California is evaluated based on eight climate projections models and the effects on water availability. The unimpaired projected streamflow for eleven California rivers, collected from Cal-Adapt, are compared with unimpaired historical flows (1950–2015) using eight climate model projections (2020–2099) identified as representative as possible future scenarios; Warm Dry RCP 4.5, Average RCP 4.5, Cool Wet RCP 4.5, Other RCP 4.5, Warm Dry RCP 8.5, Average RCP 8.5, Cool Wet RCP 8.5, and Other RCP 8.5. Projected drought deficits (or magnitudes), durations, and intensities are statistically tested against historical values to determine significance of differences between past streamflow and future streamflow. The models show significant differences between historical and projected streamflow with all three drought categories (deficit, duration, intensity), using difference in means t-tests. Warm Dry and Other simulations are projected to have larger droughts (2–3 times larger) than the historical record. Average and Cool Wet simulations are projected to have fewer droughts than the historical period. Results are consistent for 4.5 and 8.5 RCP scenarios that represent two different greenhouse gas emission levels. Potential impacts of such streamflow variations are discussed.
Highlights
Southwestern United States drought persistence increases competition among various sectors of water use, affecting economic security
Historical yearly streamflow data (1950–2015) for eleven California rivers (Sacramento River, Feather River, Yuba River, Bear River, American River, Mokelumne River, Calaveras River, Stanislaus River, Tuolumne River, Merced River, and San Joaquin River) were collected from Cal-Adapt which is an online system to access data and information on climate impacts in California [8]. These eleven river stations were selected by Pierce et al [6] who conducted climate impact assessment and identified these stations as locations in the variable infiltration capacity (VIC) hydrologic model as bias corrected to unimpaired flows that are common to the eleven stations used by California Department of Water Resources
The largest impacts are seen in drought deficits and durations
Summary
Southwestern United States drought persistence increases competition among various sectors of water use, affecting economic security. Continued dryness in the area is resulting in water level decline in various basins since 2000. Sustained dryness will result in water shortages for the immediate affected area, but other areas reliant on the basins for water. Local and state governments are implementing water conservation plans to allocate water usage [1]. The Colorado River basin will experience Tier 1 shortage in late 2021 and must implement drought contingency plans with lower basin states. Precipitation and temperature levels will be affected [2], there is a need to completely understand how water availability will be impacted
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