By Hydrosimulatics INC  

MODELING GROUNDWATER FLOW IN THE KALAMAZOO WATERSHED

The Kalamazoo Watershed is located in southwest Lower Peninsula of Michigan, United States, and drains approximately 5,200 square kilometers of  landscape into Lake Michigan. The Kalamazoo River watershed is known for its richness in biodiversity, ecosystem services and recreational opportunities, as it consists of several lakes, headwater streams, wetlands and flood plains which benefit from substantial groundwater contributions.

 However, there is growing pressure from development, urbanization, and agricultural operations that extract groundwater in the watershed as their water supply. To ensure a healthy balance between ecosystem services and addressing societal water needs, there is a need for watershed-based, sustainable management of groundwater resources made possible by big data-enabled groundwater modeling. 

OBJECTIVES

You are to develop a groundwater flow model of the Kalamazoo watershed using MAGNET to characterize the system dynamics (flow patterns and interactions with surface water bodies), evaluate data worth, and identify management implications - taking advantage of pre-processed BIG DATA to represent the geologic framework and groundwater-surface water interactions. 

Prepare a short/concise but professional report (expectation: 2-3 pages in length; but it can be more detailed if necessary), including supporting figures/screenshots in an Appendix section. Your report should address all questions listed in Part 1 and Part 2 of the analysis outlined below. 

 

Part 1 - DEM-based Seepage Model

Create a 3D watershed-based groundwater flow model where the DEM (land surface) is modeled as a surface drain, using a relatively fine grid (e.g., NX=90). 

  • Develop a graphical conceptual model representation (planview and profile); discuss boundary conditions and key sources and sinks and their model representations.
  • Simulate the flow and explain the groundwater flow patterns in the watersheds - do they make sense?
  • Visualize the seepage areas; what do they mean?
  • Visualize and explain the water budget of the aquifer. What are the most processes that control the groundwater flow pattern
  •  Compare the predicted static water levels with the observed static water levels from the statewide water well records; explain the model-data discrepancies; calibrate the model, if necessary.
  • Explain the importance of high-resolution DEM, especially the availability of LiDAR data in modeling complex groundwater systems sources-and-sinks dynamics.
  • Explain the value of such BIG DATA-based groundwater modeling in mapping groundwater dependent systems, enabling system-based conservation. 
  • Discuss the advantages and limitations of using DEM to model the effect of rivers and lakes (without explicitly incorporating the river and lake framework data). 

Part 2 - Explicit Surface Water Framework Model

Create a watershed-based groundwater model that explicitly incorporates streams and lakes, again using a relatively fine grid (e.g., NX=90). Repeat  

  • Turn of the DEM-based surface drain where the river / and lake cells are active - why is this needed?
  • Model surface water bodies as one-way head-dependent fluxes; then model surface water bodies as two-way head dependent flux boundaries.
  • Compare quantitatively the flow patterns obtained from the approach used in Part 1 (no explicit representation of the river/lake framework) and the approach used in Part 2 (explicit representation of the river/lake framework).
    • Are they consistent in terms of overall flow patterns?
    • Visualize the water budget obtained from the two approaches; are the consistent in terms of the various flow components? Why and why not?  How can the models be made consistent?

ADDITIONAL INFORMATION

Hydrogeology

The hydrogeology of this watershed is determined by thick glacial deposits of sand and gravel that contribute to permeable soils and stable groundwater inflows. Generally, there is a high degree of connection between surface and groundwater in the basin. The watershed has a gentle to moderate slope, and the drainage class is moderate to well-drained.

In some portions of the watershed, the underlying bedrock is extremely permeable and very well connected with the shallow glacial drift aquifer. In certain areas, the fractured, permeable bedrock is very shallow.  The bedrock layer thickness is unknown, but the fractured portion can be assumed to be 100ft based on the depth of the bulk of the water wells in the area.  

MAGNET / Modeling Hints

  • Use the 'Watershed from Data Center' tool to extract the Level 4 (HUC 8-digit) Kalamazoo watershed as the model domain ('Conceptual Model Tools' > 'DrawDomain' > 'Watershed from Data Center')
  • Conceptualize the subsurface as two layers - a drift layer and bedrock layer, because of the aforementioned high permeability of the bedrock in some areas.
    •  The top of the drift layer will be the land surface represented by the DEM
    • The interface between the drift layer and bedrock layer can be represented with the spatially-variable aquifer bottom surface available from the MAGNET Data Center
  • Use an effective hydraulic conductivity values for the bedrock layer; for the drift layer, a spatially-variable data layer for vertically-averaged hydraulic conductivity is available from the MAGNET Data Center (Drift K2 layer). 
  • Use the spatially-variable long-term average recharge data layer available from the MAGNET Data Center
  • Compare the simulated head (steady-state simulations) to the Static Water Level measurements available from the MAGNET Data Center ('Analysis Tools' > 'Calibration')
    •  Hint:  you can choose to draw a polygon to extract the SWL data for comparison. Simply draw a polygon the fully encompasses the Kalamazoo watershed (this is faster than choosing to extract following the domain polygon, which has many, many vertices to "check through"). 
  • Use the 'Server Stream and Lakes from Data Center' tool in the Simulation Settings tab of the domain attributes menu for Part 2:
    •  At the watershed-scale, it is not necessary to import very small streams (1st and 0th order) and lakes (small and middle)
    • Make sure that RIV cells (stream/river cells) override DRN cells (drain cells)
    • After simulating with Server streams and lakes, use the 'Overlay CnptImage' tool to overlay the stream and lake framework to the map display ('Other Tools' > 'Utilities' > 'Overlay CnptImage').