Project Description

The scope of this proposal directly relates to Research Area A, Obtaining Climate Change Information. The proposed project aims to enable the USBR to simulate and understand uncertainties in historical and future irrigation water requirements (IWR) under climate change (research area C) through the evaluation of strategies for 1) conditioning and bias correcting retrospective gridded weather data to accurately product ET for irrigated conditions, 2) downscaling General Circulation Models (GCMs) and estimating daily weather variables of temperature and precipitation using statistical, dynamical, and hybrid downscaling to increase spatial resolution of IWR estimates, and exploring empirical approaches to estimate future daily solar radiation and humidity to support use of physically-based ET equations, and 3) evaluating the impacts of the different conditioning and downscaling approaches on computed retrospective and projected reference ET (ETref) and crop ET (research area A). The proposed project also directly relates to Research Area C, Assessing Natural System's Response to Climate Change. We propose to address information gaps identified in this research area by 1) addressing the strengths and weaknesses of current IWR models and propose improvements, including nongrowing season evaporation, 2) applying retrospective and future climate information to estimate historical and future IWR using new modeling strategies for considering climate-driven variable growing season length and effective precipitation amounts, 3) providing guidance and methodologies for enhancing retrospective spatially distributed hydrologic weather data to simulate representative ETref and downscale GCMs, and 4) evaluating how climate change will impact crop dependent growing season lengths, crop development, and CO2 impacts on crop ET and IWR.