Characterizing drought in California: new drought indices and scenario-testing in support of resource management

Abstract

Introduction: California's recent drought (2012)(2013)(2014)(2015)(2016) has implications throughout the state for natural resource management and adaptation planning and has generated many discussions about drought characterization and recovery. This study characterizes drought conditions with two indices describing deficits in natural water supply and increases in landscape stress developed on the basis of water balance modeling, at a fine spatial scale to assess the variation in conditions across the entire state, and provides an in-depth evaluation for the Russian River basin in northern California to address local resource management by developing extreme drought scenarios for consideration in planning and adaptation. Methods: We employed the USGS Basin Characterization Model to characterize drought on the basis of water supply (a measure of recharge plus runoff) and landscape stress (climatic water deficit). These were applied to the state and to the Russian River basin where antecedent soil moisture conditions were evaluated and extreme drought scenarios were developed and run through a water management and reservoir operations model to further explore impacts on water management. Results: Drought indices indicated that as of the end of water year 2016 when reservoirs were full, additional water supply and landscape replenishment of up to three average years of precipitation in some locations was needed to return to normal conditions. Antecedent soil conditions in the Russian River were determined to contribute to very different water supply results for different years and were necessary to understand to anticipate proper watershed response to climate. Extreme drought scenarios manifested very different kinds of drought and recovery and characterization helps to guide the management response to drought. Conclusions: These scenarios and indices illustrate how droughts differ with regard to water supply and landscape stress and how long warm droughts recover much more slowly than short very dry droughts due to the depletion of water in the soil and unsaturated zone that require filling before runoff can occur. Recognition of ongoing conditions and likelihood of recovery provides tools and information for a range of resource managers to cope with drought conditions.

Topoclimates, refugia, and biotic responses to climate change

“…; Flint et al . ), and can also be used to assess species distributions and the potential vulnerability of vegetation to future climate change (Franklin et al . ; McCullough et al .…”

Flow regimes in coastal California steelhead trout streams: Spatiotemporal patterns in magnitude, duration and timing

“…The duration and severity of a recent multiannual drought (2012–2016) in California posed major concerns for resource managers trying to balance water use for stream organisms and humans (Flint, Flint, Mendoza, Kalansky, & Ralph, ). Current climate models project that both droughts and floods will increase in frequency and intensity in California, suggesting that the management of freshwater resources will need to anticipate even greater interannual variability in precipitation (Berg & Hall, ).…”

Competing droughts affect dust delivery to Sierra Nevada

“…In 2014, California was in the midst of a catastrophic multi-year drought (US National Climate Data Center, 2014), which was longer and warmer than any other drought the state has experienced within the past millennium (Griffin and Anchukaitis, 2014) and resulted in the lowest 12-month accumulated precipitation in California in recorded history (Swain et al, 2014). From 2012 to 2016, the drought threatened California's surface water supplies, resulted in higher rates of groundwater extraction (Flint et al, 2018), led to massive forest die-off (Asner et al, 2016), and increased wildfire intensity (AghaKouchak et al, 2014;Diffenbaugh et al, 2015;Stephens et al, 2018;van Mantgem et al, 2013). Drought impacts deepened from 2014 to 2015 with respect to increased surface water shortage for agricultural activities, resulting in a ∼33% increase in cropland fallowing from 2014 (Howitt et al, 2015).…”