EVIDENCE FOR HIGH AMPLITUDE, HIGH FREQUENCY HOLOCENE PALEOHYDROLOGICAL CHANGE FROM A SOUTHERN CALIFORNIAN LACUSTRINE SITE (LAKE ELSINORE, RIVERSIDE COUNTY)

Southern California faces an imminent freshwater shortage crisis. Essential to evaluating the magnitude of this crisis is the acquisition and development of regional proxy records of paleohydrological change. Here, we present the initial results from one of the only natural, non-playa lakes in Southern CA, Lake Elsinore (~75km SE of Los Angeles). An analysis of historical lake-level data from Lake Elsinore and winter season total precipitation show a statistically significant relationship. This relationship is strongly contingent on larger-scale ocean-atmosphere processes interacting in the eastern Pacific Ocean and their subsequent modulation of the eastern Pacific subtropical high pressure center. To extend this historical observation into the pre-historical record (i.e., Holocene), we use a multi-proxy methodology aimed at extracting the record of paleohydrology (i.e., precipitation) in the Elsinore basin through time. Using a suite of short cores from the lake’s profundal environment (<2m; n=4) and long cores from the littoral environment (8-16m; n=3), we observe cross-basin coherency in several paleohydrological proxies. Specifically, the environmental magnetic parameter, CHI, shows a strong relationship with the historic record of lake-level/winter precipitation change. Exceptionally high sediment accumulation rates in the lake’s deepest basin reveal historical hydrological change on sub-decadal timescales possibly linked to extreme ENSO/PDO events. Extension of this historical relationship between lake-level/winter precipitation and CHI, in combination with the hydrologically sensitive proxy of stable oxygen isotopes in calcite, produces a record of late-Holocene hydrological variability for Southern CA. Our initial results indicate that Lake Elsinore is subject to a wide range of hydrological variability, both high frequency and high amplitude change. Furthermore, these data indicate that the present state of Southern CA hydrology is one of relatively “wet” proportions as compared to the recent past associated with the relatively “dry” Little Ice Age. Depending on how long the present “wet” state of hydrological variability remains, Southern California’s future freshwater crisis may be of greater magnitude and more imminent than expected.