The influence of litho-stratification on the infiltrating water front in a granite terrain.

Under a sustainable groundwater development and quality management project over a semi-arid granite terrain, several rainwater harvesting structures were proposed based on geophysical investigations in the study area. In order to validate the site suitability and check the efficacy of the recommended recharge structures in terms of source sustainability, certain hydrological tests, such as infiltration studies, were conducted within the recharge area of these structures. Infiltration rate estimation using a double-ring infiltrometer normally results in an exponential decay relationship with high initial infiltration rate followed by gradual reduction until, ultimately, a stabilized rate is attained. In this paper, we present the results of infiltration tests conducted using a doublering infiltrometer (under constant head condition) within the tank bed area of a proposed percolation tank site. The results showed unique features in the infiltration rate at different time intervals within the total experimental period: a staircase-like evolution with intermittent stabilization for a short duration. Based on the integrated approach of geophysical investigations, hydrological tests, and supported by physical evidence, the infiltration behaviour observed over the study area was considered to be due to the lithological stratification with different permeability and textural conditions. [ABSTRACT FROM AUTHOR]