Date of Award

Fall 12-16-2017

Semester of Degree

December

Document Type

Open Access Dissertation

Degree Name

Ph.D. in Environmental Resources Engineering

Department

Environmental Resources Engineering

Steering Committee Member

Theodore Endreny

Steering Committee Member

Peter Groffman, David Nowak

Steering Committee Member

Philippe Vidon

Abstract

Nonpoint source pollution of nitrogen (N) and phosphorus (P) creates pervasive water quality and eutrophication problems around the world, adversely affecting rivers, lakes, and estuaries. Urban land use generates excess N and P pollutants and land use conversion removes natural N and P filtration services provided by undeveloped ecosystems. Management of these problems might first be approached using scoping level nonpoint source runoff models that are defined as balancing process complexity and algorithm simplicity, as well as balancing data availability and predictive accuracy. The contributing area / dispersal area (CADA) concept brings land cover and elevation data along with runoff and filtering likelihood algorithms into the Export Coefficient (EC) model to map likely variations in nutrient loading across the landscape. In this research, we enhance scoping level models by 1) adding spatial variation through the mapping of runoff and buffering likelihoods, 2) introducing the temporal driver of rainfall intensity to enhance nutrient export, and 3) determining the environmental variables most highly correlated with denitrification. In this study, we enhance the EC model to account for spatial and temporal variations, allowing for better estimates of nutrient loading across space and time. This research also determines key predictors of denitrification potential in mixed-use watersheds, through which denitrification hotspots can be identified. The creation of spatially- and temporally-distributed scoping models for nutrient loading through the landscape will assist managers in identifying areas of high loading potential, which generate high concentrations of nutrients and have little opportunity for downslope filtration. The identification of high denitrification potential zones also allows for facilitation of nitrate removal by routing nitrate-rich water to these zones. The low-level data needs and process-based features of the scoping model allow for its implementation into the i-Tree Hydro toolkit, a peer-reviewed software suite that is used to assess the effects of management and land use change on water quality and quantity.

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