Publication Date
8-2025
Date of Final Oral Examination (Defense)
4-11-2025
Type of Culminating Activity
Thesis
Degree Title
Master of Science in Hydrologic Sciences
Department
Geosciences
Supervisory Committee Chair
James McNamara, Ph.D.
Supervisory Committee Member
Kendra Kaiser, Ph.D.
Supervisory Committee Member
Alejandro Flores, Ph.D.
Supervisory Committee Member
David Ketchum, Ph.D.
Abstract
Western water supplies are increasingly stressed by the compounding impacts of population growth, urbanization, and climate change. Rising temperatures in Idaho are shifting precipitation patterns, with more falling as rain rather than snow. This reduces snowpack and the resulting snowmelt, which serves as the predominant water source for agriculture. At the same time, urbanization of agricultural land decreases surface permeability, replaces irrigated fields, and amplifies the impacts of climate change. The Treasure Valley, located in southwestern Idaho, has been rapidly urbanizing; urban land cover has grown by 52% from 1985 to 2021. Understanding how land use and land cover changes (LULCC) impact hydrologic processes in the Treasure Valley is critical to anticipating future shifts in water availability under a changing climate and continued urban expansion. The region’s irrigation system consists of two main components: diversions, which deliver water from the Boise River to irrigators; and drains, which return surface water and shallow groundwater to the Boise River for downstream use. Six of the fifteen major drains in the Treasure Valley have been significantly declining, particularly impacting downstream junior water rights holders late in the irrigation season. This study, conducted in collaboration with Water District 63 Watermasters and HDR Engineering, assesses how LULCC affects drainflows in the Treasure Valley. The research goals were to: (1) quantify the variable impacts of urbanization, climate, and irrigation management on drainflows from 1986 to 2020; and (2) compare 2024 drainflow gains across urban and agricultural land cover types using a water budget framework. A basin-scale statistical model was used to identify key drivers of drainflow decline, revealing urbanization has the most significant negative effect. To understand the underlying mechanisms driving this change, a field-based water budget was developed for the Mason Creek Drainage, an urbanizing agricultural watershed. Results showed that agricultural areas contributed to increased drain gains, while urban areas exhibited smaller gains and even losses over the study period. The conversion of agricultural land to urban development reduces incidental recharge and surface runoff, contributing to declining drainflows. These findings provide crucial insight for future water management and allocation in the Treasure Valley, particularly as the region contends with continued urban growth and evolving precipitation patterns driven by climate change.
DOI
10.18122/td.2393.boisestate
Recommended Citation
Beisel, Carli, "Quantifying the Impacts of Land Use and Land Cover Change on Urbanizing Agricultural Systems" (2025). Boise State University Theses and Dissertations. 2393.
10.18122/td.2393.boisestate