Abstract

Aquifer performance tests were conducted in a fractured granitic bedrock aquifer to determine the well performance and hydraulic characteristics of bore wells in a micro watershed of Kandukuru from Southern India. The long duration pump tests under constant rate conditions (ranges: 216-363 m3/day) were conducted independently at 6 bore wells to examine the variations in transmissivity. Different analytical methods were employed for the same test data, in order to extract possible variability in hydrogeological parameters. The estimated transmissivity values from different methods are in agreement with at least two of the applied methods. The transmissivity varied from 10.28 to 90.06 m2/day with mean of 33.6 m2/day whereas the specific capacity ranges between 10.40 and 67.31 lpm/m/dd. The values of both these parameters are in concurrence with each other for some tested wells. Application of multiple analytical methods confirmed that Jacob straight line method is an ideal for obtaining agreeable well hydraulic properties of fractured granitic aquifers. The tests have revealed that the sparsely fractured bedrock has feeble multi-dimensional interconnected fracture system. The lamellar hydraulic conductivity is extensive throughout the aquifer. Variations in transmissivity among the closely spaced wells exhibit heterogeneity and anisotropic characteristics. The aquifer has a trend of increasing transmissivity from southeast to northwest. The hydraulic conductivity between few extraction wells is particularly high indicating that they are connected by a highly transmissive fracture. The highly contradictory aquifer parameters within a close range pointed out that the area is subjected to selective structural disturbances. The development of secondary porosity and permeability in the form of fractures system are uneven and superficial.

Key words: Aquifer characteristics, fractured granitic terrain, transmissivity, specific capacity, bore well performance.