Application of Arc Hydro Groundwater and MODFLOW Analyst Automated well permitting

Overview Calibrated regional model is imported to ArcGIS as a “baseline” model Candidate wells are added to baseline model using well package. Impact of new well is analyzed using MODFLOW

Candidate Well Analysis Step 1: User applies for a new well (coordinates, pumping rate, screen elevations). Create a new feature in the Well feature class New Well (HydroID = 1001)

Candidate Well Analysis Step 2: Create new instances in the WEL table. CellID represents MODFLOW i, j, k values SourceID is the HydroID of the well feature Custom tool that creates MODFLOW instances based on the location of the well and the screen elevations and finds the appropriate MODFLOW cell.

Candidate Well Analysis Step 3: Export the new well data to the MODFLOW text file

Candidate Well Analysis Step 4: Run MODFLOW simulation with candidate well Use OBS process to compute new flows at rivers, drains, etc. Export drawdown file as part of solution.

Candidate Well Analysis Step 5: Read solution and compare to “base” simulation  Generate appropriate reports to guide well approval/rejection.  There can be a number of different criteria for comparison: o Changes in flows (observed vs. simulated equivalents) at key features. o Drawdown at key locations. o Drawdown maps o Capture zones (using MODPATH).

Case Study #1 - SRWMD Permitting criteria based on impact to streams, springs, etc.

Well Analysis Workflow Create new well  update well table  export well package file  run MODFLOW  import solution  build map layers

Case Study #1 - SRWMD Location of candidate well

Drawdown resulting from well

Changes in flows to sources/sinks

Case Study #2 – Virginia DEQ Virginia Coastal Plain Model (VCPM) 10-layer MODFLOW model used to analyze impacts of candidate wells Criteria based on state law - Potentiometric surface cannot fall below a critical surface (80% drawdown) - Area of Impact defined by drawdown = 1 ft Heads for layer 8

Well Permitting Workflow Create new well  update well table  export well package file  run MODFLOW  import solution  build drawdown map layer

Products Area of Impact CellsArea of Impact Contour

GIS Products

Well permitting workflow demo