Date of Award

Spring 2022

Project Type

Dissertation

Program or Major

Earth and Environmental Sciences

Degree Name

Doctor of Philosophy

First Advisor

J. Matthew Davis

Second Advisor

Anne F. Lightbody

Third Advisor

Richard B. Lammers

Abstract

Increasing population, changing climate, and on-going legacies of environmental mismanagement motivate our need for deeper understanding of the process and limits of adaptation towards sustainable management of water resources. Movements towards open-science and transdisciplinary research have enabled deeper assessments of the co-evolution of human society and changing landscapes. Policies and decisions enabling environmental restoration or sustainable resource use have been actively pursued for decades. The social barriers that prevent adaptations to succeed are deep and entrenched, but equally important are the physical barriers. Successful adaptations in water resource management need to explicitly consider the joint interactions of intervention magnitude, or intensity, over the feasible extent of its operation. While a seemingly simple concept, many solutions to water resource management would be impossible to achieve without adequate consideration of these constraints.In these three studies specific management practices were evaluated in the context of whole watershed responses and found to characterize this common constraint despite the diversity of applications. The three studies impose alternative management practices within a model of watershed-scale hydrologic processes, and the success of each practice was ultimately determined by the geographic constraints over which it could act, not by any deficiency in the policy’s capacity to affect a sufficient intensity of change. In Chapter 1, current rates of road salt loading and potential levels of aquatic habitat impairment are estimated for a New England watershed. The potential for reducing impairment through a combination of reduced salt application and buildout are investigated. Chapter 2 examines issues of aquifer sustainability in the Pacific Northwest and evaluates tradeoffs in modernizing irrigation technology. As irrigation efficiency increased less water recharged the aquifer, which exacerbated aquifer drawdown. Drawdown was offset by enhanced aquifer recharge directly from the river. The study analyzes the constraints under which aquifer drawdown can be eliminated while minimizing any reduction in streamflow. Chapter 3 evaluates the efficacy of two programs that incentivize the restoration of wetlands within the Mississippi River basin to reduce nitrogen export as nitrate export to the Gulf of Mexico. A more thorough consideration of geographic and engineering constraints on restoration illustrates how complementary management practices would be necessary to meet nutrient reduction goals. Finally, Chapter 4 analyzes the three studies and develops the concepts of intensity and extensity in successful practices in watershed management. Chapter 4 also lays out the common methodology of model experimentation in silico used throughout these studies, and defends the epistemological framework chosen.

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