The Influence of Climate Change on River Temperatures in the San Joaquin River Using Regional Climate Model Data

Abstract:

The fluctuation of water temperature in large lowland rivers is partially controlled by atmospheric conditions, such as ambient air temperature, wind speed, atmospheric pressure, longwave and shortwave radiation, vapor pressure, and relative humidity. Considering recent climate change impacts to the atmosphere and hydrosphere, it is increasingly important to understand the motivating atmospheric drivers to water temperature change in large lowland rivers so that we might mitigate negative climate change effects on our agriculture productivity, municipal and industrial water supply, and fish and wildlife management policies. Hydrologic models are a critical tool in understanding atmospheric drivers on the Earth’s water system. However, results are often limited by insufficient spatial and temporal data coverage. Here, we implement the use of a numerical hydrology model (FLUVIAL-EB) which calculates the one-dimensional heat advection equation for a specific reach of river, in tandem with Regional Climate Model (RCM) data (WRFG-CCSM). Preliminary results show the efficacy of using meteorology data from regional climate models in lieu of station data for an energy balance model that accounts for the spectral shortwave balance to more accurately predict stream temperatures in past climates. Future analysis aims to use these methods and this model to predict stream temperature in a high-emission scenario (SRES-A2) future climate state. Our analysis of the RCM observational data set supports the usefulness of the FLUVIAL-EB model as an effective predictor of stream temperature in a large lowland river, and our analysis of future climate model simulation highlights the usefulness of downscaling RCM data to regional basin level resolution for studying the relationships between atmospheric conditions and stream temperature in current and future climates, as well as provides useful scientific conclusions for use in future water management and water ecosystem policy.