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Numerical Flow Modeling II - Unsteady
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A Municipal Well Field
A municipal wellfield consists of five water supply wells. The wells are located 100 m apart along a north-south line and fully penetrate a 20-m thick confined aquifer. Estimate the drawdown 500 m west of the center well after one week, one month, one year, and one decade of wellfield operation. Solve the problem using MAGNET and an analytical approach.
(Numerical Flow Modeling II - Unsteady- 22)
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Stream Aquifer Interaction
(Lesson - Under Development) Beginner. This exercise explores the impact of stream stage fluctuations on adjacent aquifer systems (both unconfined and confined). Part I involves qualitatively describing the key parameters and relationships controlling groundwater response to stream fluctuations through the analysis of (vertical cross-section) profile models. Part II presents the mathematical framework of stream-aquifer interaction, giving students the opportunity to quantify groundwater dynamics and infer aquifer properties from observational data.
(Numerical Flow Modeling II - Unsteady- 22)
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Gradual Linear Change at the Boundary
Simulate an unconfined aquifer under direct influence of a large perennial river. Water table fluctuations are monitored by two wells placed along an average streamline of groundwater flow. The hydrographs show two episodes of a gradual increase in the water table which are consequences of the following:
1) a change in the river stage during a period without precipitation in the study area (first episode), and 2) a change in the river stage accompanied with infiltration from precipitation during a two-week period with frequent rains (second episode). Also perform sensitivity analysis and estimate aquifer properties and the infiltration rate.
(Numerical Flow Modeling II - Unsteady- 22)
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Transient Aquifer Dynamics In Response To Tidal River Fluctuation
Waves in surface water bodies will propagte into aquifer that are in direct communication with them. Develop a MAGNET model to simulate wave propagation, and compare your results with the analytical solution. Also perform a visual sensitivity analysis of your MAGNET model with respect to storage coefficient, hydraulic conductivity, and frequency of fluctuation.
(Numerical Flow Modeling II - Unsteady- 22)
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Groundwater Mounding and Baseflow Regression Dynamics
Intermediate to Advanced - Application of analytical solutions. Background: Consider the mounding of groundwater between two streams draining an unconfined aquifer (see Figure 1). A common practice is to analyze the flow in the system by assuming predominantly horizontal flow in the aquifer. The analysis may be further simplified by assuming that the change of the saturated thickness along the direction of flow (x-direction) of the aquifer is small compared to the average saturated thickness.
(Numerical Flow Modeling II - Unsteady- 22)
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Bank Sstorage and Flux Dynamics
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. Watch the related videos, answer short questions, and re-create the animations/models using MAGNET.
(Numerical Flow Modeling II - Unsteady- 22)
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Transient stream depletion
Use MAGNET to perform an evaluation of the following situation:
A well located 5000 ft from a stream which is connected to the aquifer discharges 500 gpm. The transmissivity of the aquifer is 105 ft2t/day, and the specific yield is 0.25. If pumping from the well is to be regulated so that the rate of withdrawal from the stream is less than 50% of the well discharge, how long may the well be pumped?
(Numerical Flow Modeling II - Unsteady- 22)
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Pumping near an impervious boundary
The drawdown due to pumping will be greater near the boundary when a confined aquifer is bounded on one side by a straight-line impermeable boundary. Develop a MAGNET model that can reproduce the analytical solution by applying the model to a specific situation.
(Numerical Flow Modeling II - Unsteady- 22)
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Pumping Near a Recharge Boundary
When a Confined aquifer is bounded on one side by a straight constant head boundary, drawdown due to pumping will be less near the boundary.
(Numerical Flow Modeling II - Unsteady- 22)
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Water Withdrawal Assessment
When pumping near a stream, we are interested not only in the resulting drawdowns, but also in the depletion of the stream flow, resulting in potentially adverse impact of groundwater dependent ecosystems. Develop a more general MAGNET numerical model that can reproduce the above analytical solution and perform a sensitivity analysis of stream depletion with respect to the following parameters: aquifer conductivity; storage coefficient; regional hydraulic gradient; stream bed leakance; heterogeneity; presence of other interacting sources and sinks.
(Numerical Flow Modeling II - Unsteady- 22)
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Well Interference Dispute II
Beginner to Advanced - analytical and numerical sub-problems, which can be done sequentially or individually. Background: A dispute has arisen between two farmers after one of the farmers installed a 500 GPM irrigation well 2000 ft. from the small domestic water supply well of the other farmer (see above). After the irrigation well had been operating for 3 months it was observed that the water level in the domestic well had declined over 30 feet. The owner of the domestic well claims that the decline in water level in his well is due to pumping from the irrigation well and is trying to restrict that pumping. The owner of the irrigation well claims that the decline is related to the recent drought; he has been advised that the "radius of influence"" of his well is at most 500 feet."
(Numerical Flow Modeling II - Unsteady- 22)
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Well interference Dispute III
A dispute has arisen between two farmers after one of the farmers installed a 500 gpm irrigation well 2000 ft. from the small domestic water supply well of the other farmer. After the irrigation well had been operating for 3 months it was observed that the water level in the domestic well had declined over 30 feet. Determine whether it is possible for the water level decline in the domestic well to be produced by pumping from the irrigation well.
(Numerical Flow Modeling II - Unsteady- 22)
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Well dynamics - Theis Solution
Theis (1935) presented an exact analytical solution for the transient drawdown in an infinite uniform confined aquifer. Use an analytical approach to calculate the influence of radius for the given parameters. Then develop a MAGNET model to reproduce the Theis solution and to perform sensitivity analysis with respect to aquifer parameters and pumping rate.
(Numerical Flow Modeling II - Unsteady- 22)
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Artificial recharge through wells
Artificial recharge is possible through injection wells after rainfall events for groundwater storage and recovery purposes. Use MAGNET to assess the effectiveness of an example Aquifer Storage and Recovery (ASR) project. In particular, simulate and compare the aquifer drawdown in the dry season i) with artificial well injection during the wet season; and ii) without artificial well injection during the wet season.
(Numerical Flow Modeling II - Unsteady- 22)
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Recharge Mound Growth/Decay Dynamics
When natural percolation of precipitation is insufficient to replenish groundwater withdrawn for human use, artificial recharge helps prevent aquifer depletion, subsidence and saltwater intrusion. Determine the rise in the mound below the center of a recharge basin after 15 days from the instant the infiltrated water reached the water table. If the infiltration stopped after 15 days, determine the decay in the groundwater mound 6 days later. Solve the problem using MAGNET and an analytical approach.
(Numerical Flow Modeling II - Unsteady- 22)
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Dam break and basement flooding dispute
Those Dam Guys LLC was contracted to take on an controversial project - removing the Plankton Dam along an otherwise picturesque stretch of the Plankton River. While they were using a control structure to drawdown the water level in the reservoir, the system failed, causing the downstream river levels to rise by 4m. Several citizens sued Those Dam Guys, claiming their basements were damaged because of the rising groundwater levels caused by high river levels after the dam break. The consultants argued that the basement flooding due was to the inherent surface drainage issues in the clay rich floodplain area, and had nothing to do with river level rise after the dam break. You be the judge..is Those Dam Guys LLC responsible??
(Numerical Flow Modeling II - Unsteady- 22)
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