Post on 23-Jan-2018
SWAT modeling of nutrient response to BMPs in the Beargrass Creek Watershed
Katrin Bieger, Douglas R. Smith, and Jeffrey G. Arnold2016 SWCS Annual Conference
Louisville, KY July 24‐27, 2016
Outline
1. Introduction
2. Input data and model setup
3. Preliminary results
4. Outlook
Soil and Water Assessment Tool
• Arnold et al. (1998), http://swat.tamu.edu/
• Predict the impact of land management practices on water quantity and quality in large complex watersheds
• Subdivision of the watershed into subwatersheds and Hydrologic Response Units (HRUs)
• Limited capability to identify critical source areas
1. Introduction
SWAT+
• Expected to facilitate– maintenance of code and input files– linkage of SWAT and other models– addition of new process subroutines
• Flexible spatial representation of interactions and processes within a watershed using “connect” files
• Routing of runoff, sediment and nutrients across the landscape
1. Introduction
Watershed delineation and stream definition
2. Input data and model setup
10 m DEM Resampling to 5 m
Processing using TauDEM
• Predefined watershed and streams?• Delineate riparian areas?
HRU definition
2. Input data and model setup
Land use SSURGO
Dominant soils
Land use digitized from aerial photosHydrologic Response Units
• Soil properties• Management schedules• Tile drains
Climate and streamflow
2. Input data and model setup
Observed Q at watershed outlet: 6/10/2014‐5/16/2016→ calibra on
Observed and simulated streamflow
3. Preliminary results
DailyNSE: 0.70R2: 0.75PBIAS: ‐16.4
MonthlyNSE: 0.88R2: 0.94
Water balance 2014‐2015
3. Preliminary results
Amount [mm] % of precipitation
Precipitation 1084 100
ET 609 56
Water yield 353 33
Surface runoff 242 22
Lateral flow 51 5
Tile flow 61 6
Unaccounted for 122 11
too high
too low
I have no idea what is going on here…• Error in writing output?• Error in model calculations? Source: Sanford & Selnick, 2013
“A major challenge of the ongoing evolution of the model will be meeting the desire for additional spatial complexity while maintaining ease of model use.” (Gassman et al. 2007)
HRU routing
4. Outlook
Challenges:1. Circular routing2. Roads
Implementation of BMPs
4. Outlook
Reduction efficiencies or simulation of processes?
Why use SWAT?• Identification of most effective combination of management
practices• Prediction of long‐term effects of management practices• Consideration of climate change?
Moving forward…
1. Spatial extent/parameterization of tile drains
2. Management schedules and plant growth
3. Soil parameterization
4. Calibration of water balance and streamflow
5. Calibration of nitrogen concentrations/loads
6. Implementation of BMPs in the model
7. HRU routing
4. Outlook
Thank you for your attention!
kbieger@brc.tamus.edu