Evaluation of a fractured rock aquifer (1993)

Kym L Morton
KLM Consulting Services

Abstract
Text book methods of planning and executing an aquifer evaluation programme usually emphasise primary aquifers. The secondary or fractured rock aquifer requires a more rigorous exploration programme with emphasis on the following steps: 1 Aerial photograph, satellite imagery and structural interpretation. 2. Target geophysics and resource modelling. 3. Drilling and test pumping analysis. 4. Water balance assessment and aquifer stress analysis. 5. Aquifer modelling and management. Each step has to evaluate two types of aquifer response; the response of the ground water flowing within the fractures and the response of the ground water feeding the fractures. The first response is governed by the size, distribution and orientation of the fractures. The second response is governed by the storage characteristics of the inter fracture matrix and the weathered zones in hydraulic connection with the aquifer. The neglect of one or the other during the analysis of test pumping data leads to an incorrect evaluation of the aquifer. Different methodologies are used for large regional scale as compared to village scale ground water exploration and aquifer assessment projects.

MORTON K L (1993) “Evaluation of a fractured rock aquifer, Africa needs ground water“, Ground water division of the Geological Society of South Africa