A pair of studies was performed for the CRWCD that assessed the use of Hydro-Climate Index (HCI) variables and the subsequent variable critical to water supply across Colorado. Since the state has varied basin and sub-basin topography, HCI was an ideal tool to use since it could predict the basins’ water supply by comparing them to leading indices of sea-surface temperatures and atmospheric patterns across the northern hemisphere.
To predict the water supply in these basins, HCI was used in connection with variables such as winter and spring precipitation, spring-early summer natural run-off volumes and summertime temperatures in the Colorado, Yampa/White, Gunnison, Rio Grande, San Juan-Dolores and Arkansas River basins. Additional indices that were examined include two other measures of the ENSO phenomenon, the Pacific Decadal Oscillation, and two seasonal climate indices measured in the Atlantic Ocean.
The result of these studies provided:
§ Insights into the seasonal and decadal variability of water supply components across Colorado. These relationships can be used as tools by water management interests to prepare for seasonal fluctuation in both water supply and demands that vary due to natural climatic variability.
§ Confirmation of prior research indicated that the ENSO phenomenon with wetter conditions the further south and west one is in the state.
§ Indication that the Atlantic Ocean region based indices over certain basins provided a cause-effect relationship of Colorado water supplies that are not solely driven off of the Pacific regions.
Project Highlights:
§ Comprehensive database showing long-term (50+ years) of correlations between readily measured climatic-scale variables and seasonal component of the water supply/demand system.
§ Comparisons between hydro-climate indices (HCI) and water supply variable were made with the HCI variable in a ‘leading’ mode (i.e. the HCI variable is measured before and not concurrent to the water supply variable identified). This lends to the information provided being available as a tool for providing outlooks on a seasonal and potentially longer time scales.