Simulation of hydrologic and water quality processes in watershed systems using linked SWAT-MODFLOW-RT3D model

Simulation of hydrologic and water quality processes in watershed systems using linked model Ryan Bailey, Assistant Professor Xiaolu Wei, PhD student Rosemary Records, PhD student Mazdak Arabi, Associate Professor Tyler Wible, Research Associate

Motivation Method Improve groundwater flow and solute transport processes in SWAT Link SWAT with physically-based, spatiallydistributed groundwater models

Outline Code ing Applications: Little River Watershed,

Description Linking 3 s: SWAT Code - Groundwater model - 3D finite difference RT3D - Reactive transport - 3D finite difference

Description Linking 3 s: SWAT RT3D Code ET Plant Growth Uptake Volatilization Stream stage Solute transport Groundwater discharge N, P mass loading Root Zone Processes Vadose Zone Percolation, Transport Groundwater flow N, P reactive transport canal Seepage N, P transport Pumping N, P Well Concentration Confining Layer

Description Code Linking 3 s: SWAT Soil percolation Potential ET not satisfied River Stage Pumping required N, P in percolating water N, P in stream water Daily Interactions Water Table height GW/SW Interaction Groundwater flows, sources/sinks RT3D N, P concentrations in vadose zone Mass of N, P to/from Surface Water N, P concentrations in saturated zone

SWAT Code Modification Code simulate Years Days command 1: subbasin (hru calculations) 19: / RT3D Map SWAT variables Grid Recharge (soil percolation) NO 3 concentration in percolation water Stream stage Run Run RT3D Map Grid SWAT GW Discharge Subbasin streams NO 3 loading Subbasin streams 2: Route

Disaggregated HRUs Code Grid 1. HRU DHRUs 2. DHRUs Grid Cells 3. River Cells Subbasin JAVA code map_dhru2grid.txt map_dhru2hru.txt map_grid2dhru.txt map_river2grid.txt

User Interface Code SWAT input files Input Files map_dhru2grid.txt map_dhru2hru.txt map_grid2dhru.txt map_river2grid.txt Simulation

Basin, Oregon Code Upper - USGS (2012) - 1970-2004 - 100,000 grid cells SWAT Sprague Watershed SWAT Records et al (2014) Hydrol. Earth Syst. Sci. 18: 4509 4527

Basin, Oregon Simulation Results Annual Recharge Water Table Elevation Code

Basin, Oregon Simulation Results Groundwater Discharge to Streams Code

Basin, Oregon Simulation Results Nitrate Concentration in Groundwater Code

Basin, Oregon Simulation Results Groundwater Nitrate Loading to Streams Code

Little River Watershed, Collaboration with (Katrin Bieger, Hendrik Rathjens) SWAT Code http://nsidc.org/data/docs/daac/nsidc0329_ smex03_little_river_micronet_ga.html

Little River Watershed, Collaboration with (Katrin Bieger) Code Objective: Couple SWAT with 1. Steady state model 2. transient model 3. Calibration and Testing

Little River Watershed, Collaboration with (Katrin Bieger) Code Grid River Cells Aquifer Thickness 2-10 m

Little River Watershed, Simulation Results (Steady Flow) Groundwater Head Depth to Water Table Code

Little River Watershed, Simulation Results Groundwater Discharge to Streams Code

Summary Code model Applied to two watersheds GIS/Java Pre-processing tools for linkage HRU Disaggregated HRUs DHRUs Grid Cells Grid Cells SWAT subbasins Developing: User Interface Hendrik Rathjens Create simple MODLOW model Create linkage files Public Domain (SWAT code) rtbailey@engr.colostate.edu

Thank you

Code Intersections 1. HRU DHRUs 2. DHRUs Grid Cells 3. River Cells Subbasin 1. DHRU_grid.csv 2. FullDHRU.csv 3. rivergrid.csv JAVA code map_dhru2grid.txt map_dhru2hru.txt map_grid2dhru.txt map_river2grid.txt