Dissertation
MODELING CRITICAL SOURCE AREAS OF WATER EROSION TO INFORM SOIL CONSERVATION: CONNECTING THEORY, PRACTICE, AND EFFICACY
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2021
DOI:
https://doi.org/10.7273/000003139
Handle:
https://hdl.handle.net/2376/123714
Abstract
Effective treatment of persistent agricultural erosion with limited conservation funds requires the identification of critical source areas (CSA) at the subfield scale for watershed scale planning. Publicly available data, physically-based modeling frameworks, and strong conservation district initiatives are now all in place to more directly connect conservation implementation with the underlying physical hydrology. The overall objective of this dissertation was to operationalize physical modeling simulations to identify CSA and inform strategic conservation prioritization. I developed a method for spatially distributing a simplified framework of the Water Erosion Prediction Project (WEPP) model that simulates the physical mechanisms of hillslope hydrology and erosion. A land type characterization of representative WEPP profiles was defined for spatial slope, soil, climate, and management data. Profile simulations mapped to individual flow paths in a regional watershed. This method preserved a higher resolution than the WEPP hillslope approach at 95.6% less computational cost. Simulating multiple conservation practice scenarios identified CSA at the subfield scale as well as conservation practice effectiveness. Erosion decreased by 58% for a change from uniform conventional tillage (CT) to mulch tillage (MT) and by 98% for CT to no-tillage (NT). Treatment of 25% of agricultural area effectively accounted for almost all of this reduction in erosion. Ten-meter conservation buffers were highly effective at reducing sediment delivery to the stream where erosion rates were large.
With a voluntary conservation paradigm, identifying CSA is insufficient to promote good conservation. Historically, social and financial drivers of conservation adoption have buffered implementation. A system dynamics model simulated the physical, social, and financial incentive interactions to understand conservation adoption and erosion rates under possible conservation targeting scenarios. Targeting CSA with conservation funding for land retirement with the conservation reserve program and for reduced tillage decreased the total average erosion rate by more than 50%. The most effective use of conservation funds, however, occurs when the diffusion of innovation mechanism is reinforced by broad-scale payments for tillage reduction. By identifying positive feedback, our simulations suggest large potential gains in erosion reduction and conservation fund efficiency are possible. Findings from this work can greatly enhance soil and water conservation planning.
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Details
- Title
- MODELING CRITICAL SOURCE AREAS OF WATER EROSION TO INFORM SOIL CONSERVATION: CONNECTING THEORY, PRACTICE, AND EFFICACY
- Creators
- Ames Francis Fowler
- Contributors
- Jan Boll (Advisor)Jennifer C Adam (Committee Member)Nicholas B Engdahl (Committee Member)Alexander K Fremier (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Civil and Environmental Engineering, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 141
- Identifiers
- 99900651900701842
- Language
- English
- Resource Type
- Dissertation