By Hydrosimulatics INC  

As water grows scarcer around the world, especially in semiarid and arid regions, new tools are needed to quantify aquifer storage and fluxes, including bank storage.  Bank storage is water stored in river bank sediments. At times of high water flow in rivers, water may flow laterally into the stream bank sediments adjacent to the river. This “stored” water may flow slowly back into the river or be utilized by wells. 

A. Watch videos on stream aquifer interaction under library: education video at www.magnet4water.com, and answer the questions that follow.

Video: Changes in stream stages impacting adjacent groundwater, causing groundwater levels to undergo periodic fluctuations. 

Questions: 

  • Explain what is “bank storage” stream and how it impacts base flow dynamics.
  • Discuss how 1) aquifer transmissivity, 2) aquifer storage coefficient, and 3) the frequency of stream level fluctuations impact stream and aquifer interaction
  • Explain physically and mathematically why the responses in a confined aquifer and a unconfined aquifer to stream level fluctuations are dramatically different

B. Develop a MAGNET solution that reproduces the animation above and perform a sensitivity analysis with respect to

  • storage coefficient
  • hydraulic conductivity
  • hydraulic diffusivity (defined as hydraulic conductivity / storage coefficient)
  • frequency of the river level fluctuations

Write an 1-2 page memo that summarizes the results / findings / understanding from your numerical experimentation on space-time bank storage/flux dynamics.  

MAGNET/Modeling Hints: 

  • Use ‘Synthetic mode’ in MAGNET to create a model domain.
  • Add prescribed (time-varying) zone features along the leftedges to represent the head measured at the monitoring well and lake, respectively.
  • Create one model that is unconfined by ensuring that the aquifer top elevation is greater than the maximum stream stage
  • Create another model that is unconfined by ensuring that the aquifer top elevation is less than the minimum stream stage
  • View the results in cross-section ('Analysis Tools' > 'Analysis' > 'Display Charts')