Publication Date

5-2011

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Civil Engineering

Department

Civil Engineering

Major Advisor

Venkataramana Sridhar, Ph.D., P.E.

Abstract

Warming temperatures throughout the Western United States due in part to human-induced climate change caused by the emission of greenhouse gases has been found to be responsible for 60% of the hydrologic change in the Western United States over the last half century. The hypothesis of the research is that climatic change will make planning and management based on historic climate conditions less reliable in the future. Therefore, there is a need for water management planning tools that capture feedback loops within the water-resource system so that management plans are developed that perform optimally under a wide array of inputs. This thesis explores the use of system dynamics framework to model the feedback loops associated with water management in the Snake River Basin.

The Snake River Planning Model (SRPM) was developed by the Idaho Department of Water Resources (IDWR) in FORTRAN in the 1970s, as a tool for planning and managing water resources in the Snake River Basin. The following research presents the conversion of SRPM from FORTRAN to a system dynamics platform using Powersim Studio 8. The new model is referred to as System Dynamics—Snake River Planning Model (SD-SRPM). New features in the model are a dynamic link between reservoir operations and groundwater/surface water interactions between 6 reaches of the Snake River and the East Snake Plain Aquifer through use of response functions. The response functions were generated using IDWR’s East Snake Plain Aquifer Model. SD-SRPM replicates end-of-month reservoir with an r2 value of greater than 0.70 for most reservoirs and critical reaches within the Henry’s Fork, Snake River, Boise River, and Payette River.

In addition to developing a new platform for the SRPM, this thesis explores the historic response of canal diversions in response to changes in temperature, precipitation, and streamflow within the Snake River during the period 1971-2005. The analysis of temperature and precipitation at ten climate stations throughout the basin indicates a highly significant (P < 0.10) increase in average annual temperatures. The greatest temperature increase is occurring in the spring (3.0°C) and winter (3.2°C). Due to the high natural variability of precipitation, few significant trends were found. This increase in winter and spring temperatures is driving increased springtime diversions in the basin. The early season diversions correspond to early season soil moisture conditions as represented to a strong correlation of early season diversions to the Palmer Drought Severity Index and Palmer’s z-index. Based on this analysis, a new method of determining diversion demand was developed, referred to as minimum full-supply demand.

In order to test the usefulness of the SD-SRPM model for climate impacts analysis, the model was run using bias corrected, projected flow generated by the Variable Infiltration Capacity (VIC) hydrologic model. The flow from the VIC model was based on downscaled temperature and precipitation data from three global climate models using the A1B emission scenario. The results indicate under future climate change we should expect to see a shift in the unregulated flow hydrograph, more difficulty in filling reservoirs, and perhaps a shift in where shortages occur in the basin and increased flood risk. These impacts seem to be amplified in global climate models that project greater temperature increases. The analysis of climate impacts indicates that the impacts of climate change based on the historic record may be inadequate for planning future water resource management.

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