Late Quaternary History of the Walker River: The Tale of a River with a Split Personality

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Late Quaternary history of the Walker River: The tale of a river with a split personalityKenneth D. AdamsDesert Research InstituteReno, NevadaAbstractThe Walker River is one of five major streams that flow into the Lahontan basin of northwestern Nevada and adjacent northeastern California. The behavior of this river since the late Pleistocene is quite unusual because instead of flowing into Walker Lake as it does today, at times during the Holocene it diverted to flow into the Carson Sink. When this happened, Walker Lake became a relatively dry playa whereas the Carson Sink gained a significant new water source. When the river diverted back to Walker Lake, the playa was flooded and lakes in the Carson Sink presumably shrank in size. Paleoclimatic reconstructions based on the behavior and status of lakes in both basins must therefore consider the diversion history of the Walker River.The project-PI will perform an integrated study of the behavior of the Walker River since the last highstand of Lake Lahontan and its effects on the paleohydrology of Walker Lake and the Carson Sink. This research is significant to a host of past, present, and future research efforts in the Great Basin. First, the results of this research will serve to test the hypothesis that rapid isostatic rebound after the last major lake cycle caused the Walker River to change its course. Second, fluctuations of lake levels in the Walker Lake basin may be a function of river diversion, not climatic fluctuations. Third, large short-lived lakes in the Carson Sink that displaced people, animals, and vegetation to the periphery of the Sink in the late Holocene may also be due to river diversion and not climatic fluctuations. Fourth, the results of this research will serve as revised input parameters for isostatic rebound modeling efforts. And fifth, the history and survival of the threatened Lahontan Cutthroat Trout will be placed into a new perspective that may assist recovery efforts.The research is part of a longer-term effort to reconstruct the paleoclimatic and rebound history of the Lahontan region over the last 30 ka. Recognition that rapid isostatic rebound may have invoked large-scale geomorphic and hydrographic effects underlies the importance of refining the isostatic rebound model for the Lake Lahontan basin and documenting these effects on the paleoenvironmental history of the region. The results of the proposed research will lead to a more complete paleoclimatic record from the basin and will also document the interrelationships between climate change, deep Earth processes, and surface processes.