Salt load transfer and changing salinities across a new causeway breach in Great Salt Lake: Implications for adaptive management

Abstract

Gilbert Bay, the largest embayment of the expansive Great Salt Lake (GSL) in the United States, is a productive aquatic system providing a suite of ecosystem services, both locally and across hemispheric flyways and global aquaculture networks. Gilbert Bay is currently at a record low stand and elevated salinity attributable to the coupled effects of drought and human water use in the basin. However, a recent management berm at the breach in the mid-lake causeway provides a unique adaptive management tool to mitigate harmful salinity changes. The present study measured the fluctuating Gilbert Bay salinities and salt loads across a multi-year period of changing causeway breach management. Opening of the breach in 2016 and a high spring runoff in 2017 exported a substantial portion of Gilbert Bay salt load into adjacent Gunnison Bay, lowering the salinity–elevation relationship in Gilbert. The salt load in the bay has since returned to nearly pre-breach levels with salinities at the current low stand now exceeding the ecologically optimal range. The chronicled salt movement and salinity relationships were used to recommend short- and long-term adaptive management strategies for the causeway berm in order to sustain the crucial Gilbert Bay aquatic ecosystem in the face of drought and future variability, as well as highlighting the structural advantages GSL has over other saline lakes experiencing anthropogenic water loss.