development of drain-warmf model to simulate water flow & nitrogen transport from an...
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Development of DRAIN-WARMF Model to Simulate Water Flow & Nitrogen
Transport From an Agricultural Watershed:“Subsurface Flow Component”
Shadi DayyaniShiv Prasher
Chandra MadramootooAli Madani
CSBE 2008 Annual International Meeting, July 14th
McGill University
Department of Bioresource Eng.
Main Goal:To develop and validate a model to quantify flow and nitrogen transport from an agricultural watershed
Objectives:Evaluate DRAINMOD & WARMF (surface flow) models individually for hydrology & nitrogen transport
Develop a new model (DRAIN-WARMF) linking WARMF & DRAINMOD models to:
Simulate water quantity and quality (Nitrogen) on a watershed scaleEvaluate impact of Best Management Practices (BMPs) in reducing pollution from the watershed
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Surface Flow: WARMF ModelWatershed Analysis Risk Management Framework
Watershed scale model developed by Systech Water Resources under sponsorship from Electric Power Research Institute (EPRI).
Links GIS, data, and a modeling system together in a graphical user interface (GUI).
The algorithms of WARMF were derived from many well established codes
Strong point: Surface flow componentWeak point: Subsurface flow component
WARMF Structure of WARMF
Organized into five linked modules:Engineering module is the dynamic, simulation model that drives WARMFData module provides time series input data (meteorological, point source) and calibration data Knowledge module is a utility to store important documents for the watershedConsensus & TMDL modules are roadmaps that provide guidance for stakeholders during the decision making process
Model Inputs Meteorological data
Daily values for precipitation, Min/Max temperature, Cloud cover, Dew point temperature, Air pressure, Wind speed
Sub-basin shape fileID, Area, Slop, Aspect
Land use shape fileStreams shape file
ID, Upstream sub-basin, Downstream River ID, River Length / Slope / Width / Depth, Min/Max Elevation
Model OutputsSurface flow
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Subsurface Flow: DRAINMOD
Field-scale computer simulation model developed by Dr. Skaggs in 1980
The model simulates:
Hydrology of poorly drained, high water table soils Nitrogen dynamics in the soil-water-plant system under different management practicesEffects of drainage and water management practices on water table depths, soil water regime and crop yields
DRAINMOD includes freezing, thawing, and snowmelt components
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Development of the Model (DRAIN-WARMF)
Flowchart of the DRAIN-WARMF modeling interface
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GIS (Geographic Information Systems)
Layers:Sub-basins
Drainage
Soil
Landuse
Nitrogen Application
DEM
Stream Network
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WARMF Output Processor / DRAINMOD Input File Creator
Inputs: Surface flow (each sub-basin)
Precipitation
Sub-basin layer
Outputs:(Depth of surface runoff)i
i = sub-basin’s ID
(Rainfall)i = Precipitation – (Depth of surface runoff)i
DRAINMOD Rainfall input files are created
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DRAINMOD Input File Creator1. Subdivides watershed into uniform cells
2. Derive DRAINMOD input parameters for each cell
Sub-basins (ID, Rainfall file)
Landuse (.cin file)
Soil (.sin, .mis, .wdv files; K value)
Drainage:drained / un-drained
Drainage coefficient
Drain depth / spacing
DEM (elevation)
3. Creates .gen & .prj files for each cell Store DRAINMOD input parameters for each cell and identify accompanying files (weather, cropping, soils, and hydrology)
Results in a full set of DRAINMOD input files for each cell in the watershed
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Run DRAINMOD/Output Processor
DRAINMOD simulations are run for all cells
The output processor:
Reads DRAINMOD output files (.plt)Subsurface flow depth & WTD
For drained cells, drain outflow is calculated by querying the subsurface flow depth from the .plt file for each cell
For un-drained cells, the value of WTD is taken from .plt file for each cell
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Subsurface Flow Calculator:Un-drained cells
Finds the receiving cell for each un-drained cell
Using DEM and WTDs calculated by DRAINMODCalculates the WTHcell = Elevationcell – WTDcell
Takes the ΔWTH (between the un-drained cell (a) and 8 neighbor cells)Find the Max (ΔWTH) Set the subsurface flow direction to the steepest down slope neighbor [Max (ΔWTH)]
cell “a” flows to cell 7
Calculates flow using Darcy’s law Between cell “a” and “7”
2 3
84
5 76
1
a
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Subsurface Flow Calculator:Un-drained cells
`
a
7
D
x
L
HAreaKQ
..
Cell a
Cell # 7
ΔWTDWTDa
WTD7
Ha H7
Flow Direction
Impermeable Layer
D
D
WTDxHKQ
**. 7
AreaDarcy’s Law:
X= cell size
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Watershed Subsurface Flow Calculator2 ways:
Not routedResults from each cell are summed to provide the total subsurface drainage flow for the entire watershed
Routed Using stream network (Network Analysis in GIS)
─ Calculates each cell distance to watershed outlet through streams
─ Asks for average time of concentration & the longest path
─ Calculates “time delay” for each cell
─ If time delay > 1 day then delays the flow accordingly
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Study AreaSt. Esprit Watershed
A sub-watershed of L'Assomption River in Quebec
Located ~ 50 km northeast of Montreal
Consists of 18 sub-watersheds; covers an area of ~ 25 km2; agricultural land occupies 65% of the total area
In the L'Assomption river basin, significant portion of the pollutant load comes from agricultural sources (Quebec Ministry of Environment)
St. Esprit Watershed
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Preliminary Results (Flow Simulation)
Results “Not routed”:
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bsu
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(m
m)
Observed (mm) Simulated (mm)
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Date
Su
bsu
rfac
e F
low
(m
m)
Simulated Observed
Daily total subsurface flow at outlet
Monthly total subsurface flow at outlet
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Preliminary ResultsResults “Routed”:
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1/1/
1994
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/199
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/199
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Date
Su
bsu
rfac
e F
low
(m
m)
Simulated Observed
0
50
100
150
200
250
300
Jan-
94
Feb
-94
Mar
-94
Apr
-94
May
-94
Jun-
94
Jul-9
4
Aug
-94
Sep
-94
Oct
-94
Nov
-94
Dec
-94
Jan-
95
Feb
-95
Mar
-95
Apr
-95
May
-95
Jun-
95
Jul-9
5
Aug
-95
Sep
-95
Oct
-95
Nov
-95
Dec
-95
Jan-
96
Feb
-96
Mar
-96
Apr
-96
May
-96
Jun-
96
Jul-9
6
Aug
-96
Sep
-96
Oct
-96
Nov
-96
Dec
-96
Su
bsu
rfac
e F
low
(m
m)
Observed (mm) Simulated (mm)
Daily total subsurface flow at outlet
Monthly total subsurface flow at outlet
Summary
A comprehensive evaluation of WARMF model in eastern Canada under cold condition
A comprehensive evaluation of DRAINMOD in eastern Canada under cold condition considering both drainage flow and water table depth
Development of a new model, DRAIN-WARMF, to simulate water flow and nitrogen transport from an agricultural watershed
Future Work
A comprehensive evaluation of DRAIN-WARMF for water flow and nitrogen transport
Evaluation of several BMPs for improving water quality for a given region
Thank You!