Examination of 2‐D Groundwater Recharge Solution

The analytical solution proposed by Rao and Sarma for predicting growth of groundwater mounds resulting from infiltration into bounded aquifers is examined for validity when the aquifer is assumed infinite in size. Rao and Sarma concluded that an aquifer can be assumed infinite when the ratio of corresponding linear dimensions of the aquifer and infiltration surface (A/L) is made arbitrarily large; they used $A/L=50\text{,}$ 60, and 70. Under such conditions mound height at the center should approach a constant value. Contrary to Rao and Sarma's conclusions, the writers find that maximum mound height appears to depend on the relative size of the aquifer in a specific fashion, exhibiting a maximum value when $A/L=200\text{.}$ Above this value predicted mound height gradually drops to zero. In addition, agreement among their solution, the infinite aquifer solutions published by Hantush, and a solution for circular infiltration areas derived by the writers is limited to the case where $A/L=200\text{.}$ In spite of this inconsistency, the equation proposed by Rao and Sarma may be programmed for solution without knowledge of advanced mathematical concepts. For the physical parameters used, their solution is judged to be a relatively quick and easy way to predict maximum mound height, so long as A/L is assigned a value of 200.