The figure above shows a hydrogeologic cross-section of 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 (which is roughly perpendicular to the river). The hydrographs show two episodes of a gradual increase in the water table which are consequences of the following:
- a change in the river stage during a period without precipitation in the study area (first episode), and
- a change in the river stage accompanied with infiltration from precipitation during a two-week period with frequent rains (second episode).
A. From the available data, use MAGNET to simulate the aquifer dynamics in response to the changes in the river level
B. Perform a sensitivity analysis of the model response with respect to the aquifer storage coefficient, hydraulic conductivity
C. Find the hydrogeologic parameters of the sand aquifer whose effective porosity, determined from laboratory tests of core samples, is 0.20. Specifically, determine the hydraulic conductivity, K, and the specific yield, S.
D. Find the precipitation infiltration rate during the second episode.
Graph 1: Hydrograph for episode 1: a change in the river stage during a period without precipitation in the study area (first episode)a change in the river stage during a period without precipitation in the study area.
Graph 2: Hydrograph for episode 2: a change in the river stage accompanied with infiltration from precipitation during a two-week period with frequent rains (second episode).