Deciphering the expression of climate change within the Lower Colorado River basin by stochastic simulation of convective rainfall
In drylands, convective rainstorms typically control runoff, streamflow, water supply and flood risk to
human populations, and ecological water availability at multiple spatial scales. Since drainage basin
water balance is sensitive to climate, it is important to improve characterization of convective
rainstorms in a manner that enables statistical assessment of rainfall at high spatial and temporal
resolution, and the prediction of plausible manifestations of climate change. Here we present a simple
rainstorm generator, STORM, for convective storm simulation. It was created using data from a rain
gauge network in one dryland drainage basin, but is applicable anywhere. We employ STORMto
assess watershed rainfall under climate change simulations that reflect differences in wetness/
storminess, and thus provide insight into observed or projected regional hydrologic trends. Our
analysis documents historical, regional climate change manifesting as a multidecadal decline in
rainfall intensity, which we suggest has negatively impacted ephemeral runoff in the Lower Colorado
River basin, but has not contributed substantially to regional negative streamflow trends.