Enhancing Assessment of Groundwater Vulnerability and Contamination Risk in Arid Lands

Abstract

This dissertation delves into the complexities of groundwater governance and vulnerability in Arizona, with a focus on karst and alluvial aquifer systems. It is structured around three pivotal research objectives: first, to evaluate aquifer-based differences in groundwater vulnerability and contamination risks; second, to identify disparities in vulnerability among groundwater-dependent communities; and third, to develop decision support tools that facilitate sustainable groundwater management across diverse regions. The research integrates a range of methodologies across three distinct papers, each contributing uniquely to the comprehensive analysis of groundwater vulnerability and management in arid environments like Arizona. Across all papers, the research employs a combination of spatial analysis, numerical models, hybrid index-overlay models, and statistical methods. These methodologies leverage observed secondary data, remote sensing data, and extensive groundwater monitoring data to examine various aspects of groundwater vulnerability at multiple scales. The integration of these data sources supports robust assessments of groundwater dynamics, offering a nuanced understanding of both intrinsic and extrinsic factors affecting aquifer systems. Paper 1 employs four hybrid index-overlay models—DRASTIC, DRASTIC-LUCC, DRASTIC-LUCC-AHP2, and DRASTIC-LUCC-AHP4—merging intrinsic factors like aquifer media and depth to water with extrinsic factors such as land use and climate change. The DRASTIC-LUCC model, highlighted for its efficacy in correlating nitrate concentrations with vulnerability scores, exemplifies the integration of land use and climate data into groundwater vulnerability assessments. Paper 2 focuses on equity-based disparities in groundwater vulnerability. It utilizes geostatistical tools and multivariate regression analyses to dissect the socio-hydrogeological factors impacting groundwater quality. This paper not only examines the disparities across different water supply systems and socio-economic groups but also emphasizes the need for inclusive water resource management policies that are sensitive to the needs of marginalized communities. Paper 3 explores the application of MOD16A2 evapotranspiration data in calibrating the SWAT model for the Pinal Active Management Area (AMA), emphasizing the role of agricultural land use and climate variability. This study highlights the challenges and potential of using remote sensing data to enhance hydrological models in arid regions, thereby improving the assessment of groundwater vulnerability linked to agricultural practices. The dissertation's comprehensive literature review synthesizes the existing knowledge on Arizona's groundwater policy, land use practices, and the impacts of climate change on groundwater systems. It identifies critical gaps in the current groundwater vulnerability assessment methodologies and proposes integrated approaches to enhance resilience in the face of environmental uncertainties. Through detailed spatial and numeric analyses and synthesis of findings, this dissertation advances the understanding of groundwater governance and management in arid regions, offering valuable insights for policymakers, water managers, and stakeholders. It highlights the importance of adapting management practices, integrating diverse data sources, and enhancing monitoring protocols to address groundwater contamination risks effectively. The findings support a holistic approach to groundwater management, emphasizing the necessity of sustainable practices that account for socio-economic disparities and environmental challenges in groundwater access and quality. This research contributes significantly to the field by providing a methodological framework that can be adapted for similar arid environments globally.