Watershed Symposium 2022

Linking how annual variability in climate drives 2-3 year changes in streamflow, resulting in a multi-year response of GSL volume.

When in drought, it is especially pertinent to understand how much water is available, where it is available, and when it will be available for down-stream water users and for ecological impacts on large scale ecosystems such as Great Salt Lake (GSL). Headwater catchments are the primary water suppliers and storage regions for Great Salt Lake water supplying tributaries. These catchments hold snow at high elevations and release that snowmelt as seasonal providers to seasonally recharge Great Salt Lake. Along with seasonal controls from snowmelt, headwater catchments hold water within the catchment subsurface and slowly release water throughout the dry season and into the following subsequent years, buffering lake levels even during low snow years, or exacerbating reductions in streamflow input when catchment storage is below average. This project addresses the challenge of predicting Great Salt Lake levels, and begins to address the upstream processes that lead to high or low GSL levels. Using over 118 years of historical streamflow and climate data in 10 headwater tributaries to the Jordan River and Weber River (both terminating in GSL), we identify a surprising multi-year periodicity in headwater catchment storage. This multi-year periodicity of high and low storage in the headwaters is positively related to 3-4 years of antecedent precipitation, and 2-3 years of antecedent seasonal melt rate. The previous year’s temperature is negatively related to catchment storage, suggesting that in in warmer years, headwater storage is depleted. We also find that catchment storage is directly related to GSL elevation, where high storage results in high GSL lake level, and low storage results in low GSL elevation, there seems to be a 2–3 year lag time in this relationship, suggesting that headwater catchments storage may respond at a faster time scale (1-4 years) to snowpack and temperature variability, but GSL may respond to climate patterns over a longer timescale. These findings suggest that GSL is controlled by multi-year climatic patterns that first control streamflow totals in headwater catchments and subsequently control how much water is available for runoff into GSL.