This paper examines the space-time patterns of annual, interannual, and decadal components of precipitation, temperature, and runoff (P-T-R) using long-record time series across the steep topographic gradient of the Wasatch Front in northern Utah. This region forms the major drainage area to the Great Salt Lake. The approach is to use multichannel singular spectrum analysis as a means of detecting dominant oscillations and spatial patterns in the data and to discuss the relation to the unique mountain and basin hydrologic setting. Results of the analysis show that high-elevation runoff is dominated by the annual and seasonal harmonics, while low-elevation runoff exhibits strong interannual and decadal oscillations. For precipitation and temperature, only the annual/seasonal spectral peaks were found to be significantly different from the underlying noise floor, and these components increase with altitude similar to the mean orographic pattern. Spectral peaks in runoff show a more complex pattern with altitude, with increasing low-frequency components at intermediate and lower elevation. This pattern is then discussed in terms of basin storage effects and groundwater-stream interaction. A conceptual hydrogeologic model for the mountain and basin system proposes how losing streams and deep upwelling groundwater in the alluvial aquifer could explain the strong low-frequency component in streams entering the Great Salt Lake. The phase-plane trajectories of the dominant components for P-T-R are reconstructed as a function of altitude showing the relation of hydrogeologic conditions to the strongest oscillations in mountain runoff and discharge to the Great Salt Lake. The paper shows that weak interannual and decadal oscillations in the climate signal are strengthened where groundwater discharge dominates streamflow.
All Science Journal Classification (ASJC) codes
- Water Science and Technology