Drought Impact Risk

Drought risk map legend

Drought means different things to different water users. Dry conditions turn into drought when their impacts affect urban or agricultural water users or the natural environment, just as wet conditions can lead to flooding if water overtops a levee and impacts occur.

Different water users experience drought differently, depending on the characteristics of their water supplies and their ability to manage impacts. Dry conditions can quickly lead to impacts for ranchers grazing livestock on non-irrigated rangeland or for rural residents relying on private wells tapping fractured rock groundwater sources. In contrast large urban water agencies with diverse water sources can weather multiple dry years with little impact.

Risk of drought impacts is present when precipitation is below normal levels. Risk is increased when dry conditions are coupled with above-average temperatures, as has been observed in California’s recent droughts. This map shows where precipitation for the water year to date is below 70 percent of average and temperatures are in the 80th percentile or above. This approach highlights potential risk based only on the current water year to date, showing how short-term hydrologic conditions may affect activities such as livestock grazing. Impacts are cumulative over multiple years and dry years prior to the current water year greatly increase the risk of impacts because of conditions such as reduced reservoir and groundwater storage.

This illustration of potential risk of drought impacts helps inform state drought response, but it is not the only triggering factor for state response. The broader context includes other factors such as water rights administration or special fishery protection measures. Viewers seeking information about applicability of state drought-related regulatory or financial assistance programs to their area should consult drought.ca.gov or the website of the specific program to determine the conditions being used to determine regulatory requirements or eligibility.

to see how drought risk impact changes throughout the seasons.