1. Development of DRAIN-WARMF Model to Simulate Water Flow & Nitrogen Transport From an Agricultural Watershed: “ Subsurface Flow Component” Shadi Dayyani Shiv Prasher Chandra Madramootoo Ali Madani CSBE 2008 Annual International Meeting, July 14 th McGill University Department of Bioresource Eng.

2. 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 scale Evaluate impact of Best Management Practices (BMPs) in reducing pollution from the watershed

3. 3 Surface Flow: WARMF Model Watershed 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 component Weak point: Subsurface flow component

4. WARMF Structure of WARMF Organized into five linked modules: Engineering module is the dynamic, simulation model that drives WARMF Data module provides time series input data (meteorological, point source) and calibration data Knowledge module is a utility to store important documents for the watershed Consensus & 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 file ID, Area, Slop, Aspect Land use shape file Streams shape file ID, Upstream sub-basin, Downstream River ID, River Length / Slope / Width / Depth, Min/Max Elevation Model Outputs Surface flow

5. 5 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 practices Effects of drainage and water management practices on water table depths, soil water regime and crop yields DRAINMOD includes freezing, thawing, and snowmelt components

6. 6 Development of the Model (DRAIN-WARMF) Flowchart of the DRAIN-WARMF modeling interface

7. 7 GIS (Geographic Information Systems) Layers: Sub-basins Drainage Soil Landuse Nitrogen Application DEM Stream Network

8. 8 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

9. 9 DRAINMOD Input File Creator 1.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

10. 10 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

11. 11 Subsurface Flow Calculator: Un-drained cells Finds the receiving cell for each un-drained cell Using DEM and WTDs calculated by DRAINMOD Calculates the WTH cell = Elevation cell – WTD cell 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 84 576 1 a

12. 12 Subsurface Flow Calculator: Un-drained cells ` a 7 D x Cell a Cell # 7 ΔWTD WTD a WTD 7 HaHa H7H7 Flow Direction Impermeable Layer D Area Darcy’s Law: X= cell size

13. 13 Watershed Subsurface Flow Calculator 2 ways: Not routed Results 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

14. 14 Study Area St. 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 km 2 ; 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

15. 15 Preliminary Results (Flow Simulation) Results “Not routed”: Daily total subsurface flow at outlet Monthly total subsurface flow at outlet

16. 16 Preliminary Results Results “Routed”: Daily total subsurface flow at outlet Monthly total subsurface flow at outlet

17. 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

18. 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

19. Thank You!