Hydrology of a Large, Closed Arid Watershed as a Basis for Paleohydrological and Paleoclimatological Studies in the Mojave River Drainage System, Southern California

• Main Author: Enzel, Yehouda
• Format: Text
• Language: English
• Published: UNM Digital Repository 1990
• Subjects: Geology; Pacific; Kamchatka
• Online Access: https://digitalrepository.unm.edu/eps_etds/334; https://digitalrepository.unm.edu/context/eps_etds/article/1363/viewcontent/ENZEL_HYDROLOGY_PALEOHYDROLOGICAL_CALIFORNIA_opt.pdf

A physical link between anomalous, present-day atmospheric circulation patterns over the North Pa1cific Ocean, extreme storms in southern California, the largest floods of record and lake stands in the Mojave River watershed in the Mojave Desert is demonstrated by analyzing hydrologic and climatic data. This link is then used as a modem analog to interpret hydroclimatic conditions during the latest Quaternary recorded in lake deposits in the Silver Lake playa, the terminal basin of the of the Mojave River. The Mojave River filters out small to medium floods by discharge loss through infiltration into the alluvial aquifer and allows only the extreme floods to reach the terminal playa and leave a record of the anomalous atmospheric conditions. During eight years of the 20th century storms: were vigorous enough to produce large flood events that were able to overcome the1 filtering-by-infiltration mechanism of the river, to reach the terminal playa and to produce shallow lakes. Each of these floods was due to precipitation with a durati1on of one or two days resulting in rainfall of greater than +2 standard deviations from the mean monthly precipitation in the headwaters of the Mojave River. These precipitation events occurred in response to extreme southerly displacement of both the winter storm activity and the Polar jet over the eastern North Pacific, directing subtropical moisture into southern California. Analyses of sea-level pressure (SLP) for the eight months with lake­building floods revealed that a) the eastern North Pacific subtropical high weakened, giving way to an anomalously low pr1essure system along the west coast of the United States, b) the central North Pacific winter low shifted to the east and south, c) there is a tendency for a 'split' Akutian low with higher than normal SLP in the Aleutian and an anomalously low SLJP over Kamchatka. The historic lake-building storms and floods are relatively rare; however, they control the daily to decadal hydrological records of the Mojave River hydrologic ...