Hydrometeorological controls of fluvial suspended sediment transfer and lake sedimentation at Eklutna Lake, Alaska

Authors: Erik Schiefer*, Northern Arizona University, Jason Geck, Alaska Pacific University, Michael Loso, National Park Service, Johnse Ostman, US Geological Survey, Nicholas McKay, Northern Arizona University, Darrell Kaufman, Northern Arizona University
Topics: Geomorphology, Water Resources and Hydrology, Mountain Environments
Keywords: suspended sediment, climate, floods, Eklutna Lake, Alaska
Session Type: Paper
Day: 4/5/2019
Start / End Time: 9:55 AM / 11:35 AM
Room: 8224, Park Tower Suites, Marriott, Lobby Level
Presentation File: No File Uploaded

Suspended sediment transfers in proglacial lake catchments are sensitive to a wide range of hydrometeorological controls. We have analyzed these controls over instrumental record periods for Eklutna Lake (61.38°N 149.04°W), in the western Chugach Mountains of south-central Alaska, where sediment transfer is of interest because of site reservoir and water supply operations, and because the lake sediment deposits may contain a valuable proxy signal of regional floods. Discontinuous discharge, water turbidity, and suspended sediment concentration data has been collected for the two primary inflows to Eklutna Lake (2009-2018), with overlapping meteorological data available from a SNOTEL weather station site within the lake catchment. We used a genetic algorithm approach with the R package glmulti to automate optimal model selection and multi-model inference in the multivariate modeling of fluvial sediment transfer. Best-fit models, derived from large sets of potential hydrometeorologic explanatory variables, relate sediment transfer to a wide variety of variable interactions and temporal trends among discharge conditions and climatic controls, involving both temperature and precipitation. In 2017, we collected and analyzed 38, spatially distributed, short (<1 m) sediment cores from the lake. Sediments deposited during the last half century are discontinuously varved (annually laminated), and contain many relatively coarse and thick marker beds which we have correlated to specific floods from regional hydrometric records. We use this sedimentary record of flooding to explore magnitude-frequency relations during this recent period of rapid environmental change, and to contrast spatiotemporal patterns of extreme- and average-regime sedimentation within the Eklutna Lake basin.

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