HYDROLOGIC SCENARIOS FOR SEVERE SUSTAINED DROUGHT IN THE SOUTHWESTERNUNITED-STATES

This paper considers the risk of drought and develops drought scenario s for use in the study of severe sustained drought in the Southwestern United States. The focus is on the Colorado River Basin and regions t o which Colorado River water is exported, especially southern Californ ia, which depends on water from the Colorado River. Drought scenarios are developed using estimates of unimpaired historic streamflow as wel l as reconstructions of streamflow based on tree ring widths. Drought scenarios in the Colorado River Basin are defined on the basis of annu al flow at Lees Ferry. The risk, in terms of return period, of the dro ught scenarios developed, is assessed using stochastic models.