Thesis
Increasing the resolution of a global nitrogen export model: Applications and advances in central California
Washington State University
Master of Science (MS), Washington State University
2010
Handle:
https://hdl.handle.net/2376/103035
Abstract
Modeling of land-based sources and landscape sinks of N provides insight into mechanisms controlling N transport downstream through watersheds. While much work has been done on both small-scale, process-based models and large-scale models of N transport, there still exists a need for easy-to-use sub-basin scale models that can estimate sources of N in river export. Our objectives for this study were to test the scalability of a global model of nutrient export (NEWS2-DIN: Nutrient Export from Watersheds- Dissolved Inorganic Nitrogen) both spatially and temporally and to use this model to produce the first estimates of sources of DIN export from the sub-basins of central California. The model was down-scaled spatially for application to the sub-basins of central California, and down-scaled temporally to test the ability of the model to capture sub-annual N dynamics. Modifications to the global model include a lower transfer efficiency of terrestrial inputs to surface waters for natural versus anthropogenic N sources. For the linear relationship between runoff and DIN loading to surface waters, the watershed export coefficient, e, was set to 0.94 for anthropogenic diffuse N inputs and 0.1 for natural diffuse N inputs. We use this downscaled model, NEWS2-DINSB (SB for Sub-Basin) to investigate patterns and controls of DIN sources and river export in 15 sub-basins of central California as well as the Sacramento and San Joaquin basins. There was a reasonable agreement between observed DIN load and yield (kg N yr-1 and kg N km-2 yr-1, respectively) and modeled river load and yield from the California basins (Nash-Sutcliffe efficiency R 2 =0.76 and R 2 = 0.49, load and yield respectively). Model results also show DIN export from all basins is dominated by anthropogenic N sources (52-99% of yield), particularly fertilizer and manure. These results suggest that even in systems where the major fraction of watershed N inputs consists of natural N-fixation or atmospheric deposition, DIN export is highly sensitive to agricultural N inputs. Sub-annual model performance varied by basin and indicated that more work must be done to represent sub-annual N dynamics with NEWS2-DINSB.
Metrics
7 File views/ downloads
12 Record Views
Details
- Title
- Increasing the resolution of a global nitrogen export model
- Creators
- Kara Elizabeth Goodwin
- Contributors
- John A. Harrison (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Environment, School of the (CAHNRS)
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525137101842
- Language
- English
- Resource Type
- Thesis