DROUGHT ANALYSIS WITH RESERVOIRS USING TREE-RING RECONSTRUCTED FLOWS

This paper presents a drought study of the Sacramento River of Califor nia considering the presence of reservoirs. A total of 508 years (1485 -1992) of annual flow data are used. The data prior to 1872 was recons tructed from tree-ring data of Oregon and California using statistical and stochastic techniques. Runs analysis is used to investigate the d rought characteristics for three cases: (1) No reservoir; (2) a reserv oir with a myopic release rule; and (3) a reservoir with an anticipato ry release rule. It is found that: (1) The tree-ring reconstructed flo ws in this study are better than a previous data reconstruction; (2) t he reconstructed data showed that other severe droughts occurred prior to 1872, when historical records were available, thus there are risks involved in relying solely on the historical data; (3) the Sacramento River basin experienced the most severe droughts around the 1580s and 1930s; and (4) the results of the cases with reservoirs have signific antly longer interarrival times between drought events, a much smaller number of drought events, and much less severe water shortages and cu mulative deficits in contrast to the results with no reservoir.