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Predictions and Limits to Prediction

The Great Salt Lake basin region exhibits extreme inter-annual climate variability, with some of the largest coefficients of variation of precipitation in the country. Few hydrologic models are able to represent the complexity of western mountain systems, of which climate variability is part. This variability provides a good setting for the study of climate-hydrology interactions and gives rise to the following question:

How can we better predict natural and human induced changes in the hydrologic cycle so as to plan for and adapt to changes and uncertainties in water resources in a water-stressed semi-arid snowmelt driven system?

Total annual precipitation can vary to a huge degree from year to year within the Great Salt Lake Basin (figure below for Salt Lake City), and annual precipitation values tend to be located either above or below the average, with fewer years located near the average value (shown as the horizontal red line).

Precipitation data from Salt Lake City NWSFO, Utah (427598)
Source:  Western Regional Climate Center

Fluctuations in the Great Salt Lake volume represent the integrated effects of precipitation, snow pack sublimation, and subsurface transport over the watershed. Hence, there is sometimes not a strong correspondence between precipitation and streamflow (figure below), reflective of the difficulty in quantifying basin wide precipitation inputs. Note also that major changes in lake volume lag behind changes in precipitation and streamflow indicating influence of subsurface transport and possibly other processes influencing lake volume fluctuation.

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