Changing climatic conditions in the Colorado River Basin: Implications for water resources management in the Las Vegas Valley

Summary This study focuses on the effects of climate variability and climate change on the Colorado River flow as well as on implications for water resources management. A system dynamics model was developed for the Colorado River Basin, operating at a monthly time scale from 1970 to 2035. Changes in streamflow were simulated with a hydrologic model that used outputs from 16 global climate models (GCMs) and 3 emission scenarios. Lake Mead levels – as well as the corresponding probabilities of supply curtailments to the Basin states dependent on the Colorado River – were evaluated based on the changes in streamflow estimated using GCM projections. Lake Mead levels were evaluated with regard to a reduction in supply to the Basin states. Ensemble averages of the GCMs for each emission scenarios indicated an increase in temperature, on average by 0.84 °C over the period of 2012–2035. The magnitude and direction of change in precipitation varied among ensemble of GCMs for different emission scenarios, with A1b showing a decrease and A2 and B1 showing an increase. Ensemble average shows a small increase in precipitation by about 0.4%. An ensemble average reduction in streamflow by about 3% was observed until 2035. This reduction resulted in significant effects on the water supply to the Basin states, with varying reliability values for water supply. Although the median of the ensemble flow resulted in no probability of Lake Mead levels dropping down below 305 m, results varied from 0% to 46% for individual GCMs for A1b scenario. This study may help water managers in long-term planning and management of water resources to meet the future water demands.