Remote Sensing Spatial Tools and Modeling to Characterize the Impact of Climate Change on Snowmelt Runoff and Irrigation Water Supply
Over 3 million acres of farmland are irrigated across the Snake River Plain in southern Idaho, representing roughly one-half of the irrigated acreage in the Pacific Northwest. Irrigation demands total some 12 million AF of diversions. At present irrigation water demands occupy the dominant use of water across the Snake River Plain and as a result, irrigated agriculture occupies a significant fraction of the region's economy. The primary source of this water is winter precipitation which accumulates as snow at high elevations and produces snowmelt runoff during the spring season. Knowledge of the magnitude of the annual accumulation and timing of the spring snowmelt runoff is crucial for forecasting and operations, for policy- and decision-makers in federal and state agencies, and for legislative bodies, as well as Idaho stakeholders whose
livelihoods are directly affected by water availability. Several problems regarding water supply have manifest themselves. First, annual accumulated precipitation and volume of runoff have varied by a factor of 2 to 3 over the past 25 years alone. Additionally, snowpack over the past half century has decreased throughout the Pacific Northwest. Accurate representation of the behavior of natural systems with driving conditions outside the normal range of observations will require synthesis of conditions representative of potential climate scenarios and process-based modeling approaches. Conditions required to be synthesized are weather and climate scenarios, and snow depletion characteristics. For this research, we will make use of data for Idaho extracted from multiple climate scenarios generated by international numerical climate modeling groups, and collaborate with other groups whose
emphasis includes generating spatially distributed data sets for Idaho. We will concentrate our work on developing methods to generate snow depletion characteristics through a statistical analysis of historical depletion maps produced from satellite remote sensing and ground based snow observations. We will identify the interannually persistent patterns of melt, as well as the characteristics of interannual variability, and from this generate snowmelt patterns that are suitable for various climate change scenarios. From this we will develop a database which can be used by others for snowmelt modeling, specifically within the basin addressed in this research, and to other basins by applying the methods developed in this research to other basins. Secondly, we will incorporate this snowmelt depletion product into a snowmelt model which incorporates the realism of physical processes and
setup the model for the Upper Snake River Basin. Lastly, we will work with state and federal agencies to incorporate the work and products developed here into operational and planning models for water supply. The expected outcomes are a new method for generating snowmelt depletion maps, a database of snowmelt depletion maps, improved methods for simulating snowmelt runoff, databases of the impact of a number of climate change scenarios on water supply and scientific publications to disseminate the methods developed.