Late Quaternary history of the Walker River: The tale of a river with a split personality

Affiliation(s)PIProject PeriodFunded by
DEES

Adams, Kenneth D

February 2001 - January 2003 This material is based upon work supported by the National Science Foundation under Grant No. EAR-0087840

Keywords:Walker river, quaternary history, Lahontan basin, Walker lake

Project Description

Walker River
                   Walker River

The 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 goal of this project is to delineate 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:

  • 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.
  • Fluctuations of lake levels in the Walker Lake basin may, in part, be a function of river diversions and not solely climatic fluctuations.
  • 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.
  • The results of this research will serve as revised input parameters for isostatic rebound modeling efforts.

Standard geologic and geomorphic techniques are being used to determine the diversion history of the Walker River including mapping fluvial terraces and channels on aerial photographs, stratigraphic and sedimentologic description, collecting samples for age control, coring channel remnants with a Giddings coring rig, and surveying channel remnants with a Total Station. Field efforts are concentrated in five main areas including Adrian Valley, northern Mason Valley, the point of diversion near Yerington, NV, the lower Walker River near Walker Lake, and low elevation shorelines rimming the Carson Sink.

This 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 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.