Comparative analysis of SWAT model with Coupled SWAT-MODFLOW model for Gibbs Farm Watershed in Georgia

Transcription

1 2018 SWAT INTERNATIONAL CONFERENCE, JAN 10-12, CHENNAI 1 Comparative analysis of SWAT model with Coupled SWAT-MODFLOW model for Gibbs Farm Watershed in Georgia Presented By K.Sangeetha B.Narasimhan D.D.Bosch A.W.Coffin

2 Future Work 2 Outline of the Study Motivation Study Area Description Gibbs farm watershed Methodology Model setup Results and Discussions Conclusion

3 Motivation 3 Streams and lakes interact with adjacent aquifers and need to be treated together in water resource assessment. For efficient water resource management, linkage between SW & GW is essential Many models are integrated for understanding the SW-GW interaction (SWAT MODFLOW) This study attempts to demonstrate and analyse the application of SWAT model with recently developed GUI (SWATMOD-PREP)

4 Deep Aquifer Shallow Aquifer Revap Soil Profile Plant Transpiration Soil Evaporation 4 (Contd..) Precipitation Surface Runoff SWAT considers each HRU and sub- basins as separate 1-D unit Sub Surface Lateral flow Spatial locations of each HRU - sub-basins are not considered Percolation/GW Recharge GW Model lacks in simulating the GW Flow distribution and recharge rates for Percolation watershed

5 Study area Gibbs Farm Watershed

6 (Fox Den Field) Description of Study Area 6 Gibbs Farm Watershed, TIFTON, Georgia Intensive agriculture and dense riparian forest buffers along stream channels Geology : Hawthorne formation by quartenary sands and surface soils top of landscape and 2.5 below land surface ) Area of watershed : 115 hectares ; Soil : Loamy sand with TIFTON loamy sand Annual Mean Precipitation : 1200 mm; Monitoring Wells : 29 wells

7 Overview Of Coupled SWAT-MODFLOW 7 Linking 3 Models: SWAT MODFLOW RT3D Graphical User Interface - SWATMODPREP Uptake Volatilization Stream stage Solute transport Groundwate r discharge N, P mass loading ET Root Zone Processes Plant Growth Vadose Zone Percolation, Transport Groundwater flow N, P reactive transport canal Pumping N, P Well Concentration Confining Layer Source : Ryan Bailey et al, SWATMODFLOW Tutorial, February-2017

8 Methodology 8 SWAT MODEL Digital Elevation Model (DEM) Landuse Map Soil Map Slope Map Weather data Manual Calibration Run SWAT Model Calibrated txtinout folder View Coupled SWAT-MODFLOW Result Spatial Setup Import Subbasins, HRU and river shapefiles Disaggregate HRUs Intersect MODFLOW Grid cell with DHRUs Identify River Cells Write linkage files SWATMOD-PREP MODFLOW Import DEM Aquifer Properties (S y S s, Aquifer Thickness, Hydraulic conductivity) Initial Conditions Simulation Enter the period of simulation Table of observation cells MODFLOW OUTPUT

9 Coupled SWAT- MODFLOW MODEL (SWATMOD-PREP) 9 Developed for exchanging the characteristics between HRU s of SWAT model and grid cells in MODFLOW model GW module in SWAT is replaced by MODFLOW Coupled model simulates the spatial- temporal GW recharge and Stream aquifer interactions by RIVER Package in MODFLOW

10 Read SWAT input files Read Inputs Read MODFLOW input files Read SWAT - MODFLOW linkages files 10 (Subbasin and HRU calculations) (Aquifer Properties and Initial conditions) (hru2dhru.txt dhru_grid.txt grid_dhru.txt river_grid.txt) Coupled SW-GW model SWAT output (Subbasin and HRU calculations) Linkage of SWAT - MODFLOW (Convert the SWAT HRU variables to MODFLOW variables) MODFLOW SWAT-MODFLOW Linkage Compute GW Hydraulic Head Linkage of SWAT MODFLOW (Convert the MODFLOW Grid variables to SWAT HRU variables) SWAT (Route Stream network to the outlet) - Percolation (mm) - ET - Depth of river GW discharge to streams Simulate next day - Percolation (mm) - ET - Depth of river

11 SWAT Model Input Data 11

12 SWAT Model Input Data 12 Landuse : North basin (more crops in plastic covered beds) and south basin ( more ponds and less land for crops)

13 Effect of Ponds in the Watershed 13 Farm ponds agricultural source for the watershed in the south basin and also for irrigating the north basin fields. Ponds constructed on Miocene Hawthorne formation which act as Aquiclude Ponds store stream flow and utilized for irrigation Water is pumped from Floridan aquifers at a depth of m below land surface mostly surface and shallow GW

14 Pond Simulation in the watershed 14 Name of Pond Fraction Surface area Volume Subbasin Basins (%) (Hectares) (*10 4 m 3 ) number North Basin South Basin South Basin

15 SWAT Model Setup 15 Simulation periods : January 1995 through December 2004 Warm up period : January 1995 through December 1997 Calibration sites : U/S Stream gauge :8924 ; D/s Stream gauge : 8922 Validation sites : U/S stream gauge : 8923 ; D/s Stream gauge : 8921 Observed data : Stream flow ( January 1998-December 2004) Model performance indices : NSE and R 2 Pond simulation in both north and south basin

16 Sim/Cal flow (m3/s) Results and Discussions SWAT model Flow Hydrograph Year observed flow (cms) SIM_WITH WATERUSE_PONDS Calibrated flow (m3/s)

17 Jan-98 Mar-98 May-98 Jul-98 Sep-98 Nov-98 Jan-99 Mar-99 May-99 Jul-99 Sep-99 Nov-99 Jan-00 Mar-00 May-00 Jul-00 Sep-00 Nov-00 Jan-01 Mar-01 May-01 Jul-01 Sep-01 Nov-01 Jan-02 Mar-02 May-02 Jul-02 Sep-02 Nov-02 Jan-03 Mar-03 May-03 Jul-03 Sep-03 Nov-03 Jan-04 Mar-04 May-04 Jul-04 Sep-04 Nov-04 Sim/Cal flow (m3/s) (Contd..) Flow Hydrograph Year OBSERVED SIM_WITH WATERUSE_PONDS Calibrated flow (m3/s)

18 Jan-98 Mar-98 May-98 Jul-98 Sep-98 Nov-98 Jan-99 Mar-99 May-99 Jul-99 Sep-99 Nov-99 Jan-00 Mar-00 May-00 Jul-00 Sep-00 Nov-00 Jan-01 Mar-01 May-01 Jul-01 Sep-01 Nov-01 Jan-02 Mar-02 May-02 Jul-02 Sep-02 Nov-02 Jan-03 Mar-03 May-03 Jul-03 Sep-03 Nov-03 Jan-04 Mar-04 May-04 Jul-04 Sep-04 Nov-04 Sim/Cal flow (m3/s) (Contd..) Flow Hydrograph Year observed flow (cms) SIM_WITH WATERUSE_PONDS Calibrated flow (m3/s)

19 Jan-98 Mar-98 May-98 Jul-98 Sep-98 Nov-98 Jan-99 Mar-99 May-99 Jul-99 Sep-99 Nov-99 Jan-00 Mar-00 May-00 Jul-00 Sep-00 Nov-00 Jan-01 Mar-01 May-01 Jul-01 Sep-01 Nov-01 Jan-02 Mar-02 May-02 Jul-02 Sep-02 Nov-02 Jan-03 Mar-03 May-03 Jul-03 Sep-03 Nov-03 Jan-04 Mar-04 May-04 Jul-04 Sep-04 Nov-04 Sim/Cal flow (m3/s) (Contd..) Flow Hydrograph Year OBSERVED SIM_WITH WATERUSE_PONDS Calibrated flow (m3/s)

20 Challenges in Model Calibration 20 In north basin, more cropland and in south basin, more ponds In south basin, Ponds decrease surface runoff and increase baseflow and north basin almost all vegetables plastic covered which increases surface runoff Parameters was slightly different for both because of significant difference in north and south basins

21 Performance Indices for both Upstream and Downstream sites 21 Name of Stream Gauge Daily Values (Simulated) Monthly Values (Simulated) Daily Values (Calibrated) Monthly Values (Calibrated) R 2 NSE R 2 NSE R 2 NSE R 2 NSE

22 Jan-98 Mar-98 May-98 Jul-98 Sep-98 Nov-98 Jan-99 Mar-99 May-99 Jul-99 Sep-99 Nov-99 Jan-00 Mar-00 May-00 Jul-00 Sep-00 Nov-00 Jan-01 Mar-01 May-01 Jul-01 Sep-01 Nov-01 Jan-02 Mar-02 May-02 Jul-02 Sep-02 Nov-02 Jan-03 Mar-03 May-03 Jul-03 Sep-03 Nov-03 Jan-04 Mar-04 May-04 Jul-04 Sep-04 GW Head (m) Results and Discussions (SWATMOD-PREP) 22 P Observed GW Head (m) Simulated GW Head (m) Year

23 GW HEAD (M) (CONTD..) P YEAR Observed GW Head (m) Simulated GW Head (m)

24 GW HEAD (M) (CONTD..) YEAR Observed_8906 Simulated_8906

25 MODFLOW HEAD 25

26 DEPTH TO WATER LEVEL PLOTS 26

27 SWAT RECHARGE 27 Recharge values range from m

28 GW SW INTERACTION SWAT 28 Seepage to aquifer range from to m 3 /d

29 Jan-98 Mar-98 May-98 Jul-98 Sep-98 Nov-98 Jan-99 Mar-99 May-99 Jul-99 Sep-99 Nov-99 Jan-00 Mar-00 May-00 Jul-00 Sep-00 Nov-00 Jan-01 Mar-01 May-01 Jul-01 Sep-01 Nov-01 Jan-02 Mar-02 May-02 Jul-02 Sep-02 Nov-02 Jan-03 Mar-03 May-03 Jul-03 Sep-03 Nov-03 Jan-04 Mar-04 May-04 Jul-04 Sep-04 Nov-04 Sim/Cal flow (m3/s) SWAT FLOW HYDROGRAPH Flow Hydrograph Year observed flow (cms) SIM_WITH WATERUSE_PONDS Calibrated flow (m3/s) modflow_calibrated(m3/s)

30 Findings and Future work 30 SWAT model need to calibrated for SW processes MODFLOW model need to be calibrated for GW processes Comparative study of SWAT model with numerical techniques (Finite Element Method and Finite Difference Method) and Analytic Techniques (Analytic Element Method)

31 Thank You For Your Attention 31