Estimating Nitrate Transport in Surface-Subsurface ... · Tyler Wible •Model Overview •Model...
Transcript of Estimating Nitrate Transport in Surface-Subsurface ... · Tyler Wible •Model Overview •Model...
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Estimating Nitrate Transport in Surface-Subsurface Hydrologic Systems by the linked SWAT-MODFLOW-RT3D Model
Xiaolu WeiRyan Bailey
Rosemary RecordsMazdak Arabi
Tyler Wible
• Model Overview
• Model Linkage
• Applications: Klamath Basin, OR
Outline
Overview
Model Overview Klamath Basin, ORModel Code
SWAT
MODFLOW
RT3D
- Groundwater model
- 3D finite difference
- Reactive transport
- 3D finite difference
Method: Link SWAT with physically-based, spatially-distributed groundwater models.
RT3D Introduction
Reactive Transport in 3 Dimensions
Dispersion Advection
Sources and Sinks
Reactions
(first-order kinetics)
Model Overview Klamath Basin, ORModel Code
RT3D Introduction
Reactive Transport in 3 Dimensions
• Finite Difference Method
• Same grid as MODFLOW
• Flows/SS from MODFLOW
Model Overview Klamath Basin, ORModel Code
Overview
Model Overview Klamath Basin, ORModel Code
SWAT-MODFLOW
Model Overview Klamath Basin, ORModel Code
MODFLOW Grid
Disaggregated HRUs
1. HRU Grid
2. River Cells Subbasin
Recharge
GW Discharge
(Pre-processing tools)
Soil Percolation
Potential ET not satisfied
River Stage
SWAT
N, P in percolating water
Pumping required
N, P in stream water
MODFLOW
GW/SW Interaction
Water Table Height
Groundwater Flows, Sources/Sinks
RT3D
Mass of N, P to/from Surface Water
N, P concentrations in vadose zone
N, P concentrations in Saturated Zone
Daily Interactions
Linking Three Models
Model Overview Klamath Basin, ORModel Code
Klamath Basin, Oregon
SWAT Model
MODFLOW ModelUpper Klamath
SWAT Model
- USGS (2012)- 1970-2004- 100,000 grid cells
Records et al (2014)Hydrol. Earth Syst. Sci. 18: 4509–4527
Model Overview Klamath Basin, ORModel Code
Simulation Results
Nitrate Concentration in Groundwater
Model Overview Klamath Basin, ORModel Code
High: 1.26 mg/L
Low: 0 mg/L
Simulation Results
Model Overview Klamath Basin, ORModel Code
Groundwater Discharge to Streams
Simulation Results
Model Overview Klamath Basin, ORModel Code
Groundwater Nitrate Loading to Streams
Simulation Results
Model Overview Klamath Basin, ORModel Code
Stream loading comparison
Simulation Results
Model Overview Klamath Basin, ORModel Code
Frequency Plot
0
0.1
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0.5
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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 More
Freq
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cy
NO3-N Concentration (mg/L)
Observed Data
Simulated _ Surrounding Wells
Simulated _ Entire Basin
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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 More
Freq
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cy
NO3-N Concentration (mg/L)
Observed Data
Simulated _ Surrounding Wells
Simulated _ Entire Basin
Future work
- Keep increasing N leaching from SWAT
- Balance stream flow, stream loading, and leaching
- Applied to Arkansas River Basin
- Developing: ArcGIS interface
AcknowledgementFunding
Acknowledgements
Box Plot for different Land Use
Simulation Results
Model Overview Klamath Basin, ORModel Code
NO
3-N
Co
nce
ntr
atio
n (
mg
/L)
Code Structure
Model Overview Klamath Basin, ORModel Code
simulate
Read/Allocate arrays MODFLOW / RT3D
Years
Days
command
1: subbasin (hru calculations)
19: MODFLOW / RT3D
HRU values disaggregated HRUs (DHRUs)
DHRUs Grid cells
River stage MODFLOW River cells
Run MODFLOWRun RT3D
Map SWAT Grid
Map Grid SWATGW Discharge Subbasin streams
NO3 loading Subbasin streams
2: Route
NO3 in percolation
NO3 in river water
Denitrification
Surface
Aquifer
Routine