The Great Salt Lake Basin Study (GSLBS) is evaluating long-term water management strategies under a wide range of uncertain future hydroclimatic conditions. A critical component of this effort is the development and characterization of climate scenarios used to support hydrologic simulation, water resources planning, and risk-informed decision making. This study evaluates an ensemble of 101 hydroclimate traces derived from 31 General Circulation Models (GCMs) statistically downscaled using the Multivariate Adaptive Constructed Analogs (MACA) framework.

Rather than focusing on individual climate projections, the analysis characterizes the distribution and uncertainty spread of future hydroclimatic conditions across the ensemble. Multiple statistical methods were applied to precipitation, temperature, and derived hydrologic indicators, including trend analysis, hydroclimatic performance metrics, step-change detection, principal component analysis (PCA), generalized extreme value (GEV) analysis, and heteroscedasticity assessment. These complementary approaches provide insight into projected changes in central tendency, variability, persistence, extremes, and nonstationarity. The results are used to identify dominant patterns of hydroclimatic change, quantify uncertainty across projections, and support the selection of representative climate scenarios for subsequent modeling efforts within the Basin Study.

This work provides a transparent and reproducible framework for evaluating large climate ensembles and translating climate uncertainty into planning-relevant information. The characterization of uncertainty across statistically downscaled projections supports the development of robust adaptation strategies and helps inform future evaluations of water supply reliability, system vulnerability, and operational performance. Ongoing work will compare the MACA-based ensemble with dynamically downscaled simulations generated using the Weather Research and Forecasting (WRF) model to assess differences in projected hydroclimatic behavior and their implications for long-range planning in the Great Salt Lake Basin.