Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

J. P. Kukillaya ¹, K. Padmanabhan ², E. Krishnan ²

Affiliations
1 IX 695C, "Chetas", Erattakannanpalam, Talap, Pallikunnu P.O., Kannur, Kerala, IN
2 Kerala Samuhya Jalasechana Samithy, Thrissur - 5, Kerala, IN

Abstract

Short and medium duration pumping test data from a well-field, in conjunction with outcrop fracture pattern studies, are used to understand the nature of a system of fracture aquifers in a metamorphic terrain in Kerala State. Satellite imagery shows a minor E - W lineament intersecting a major regional NNW - SSE lineament in the area. Drawdown and time lag data indicate greater connectivity along the minor lineament compared to the major one. The E - W elongation of the drawdown contours correlates with dominant E - W fracture sets seen on outcrops. The NNW - SSE fracture zone probably forms a regional conduit for groundwater flow, with the degree of hydraulic. connectivity modified locally by other intersecting fracture zones. A large-scale heterogenity in the form of an E-W fracture zone is indicated in this area. The pumping tests give responses similar to double-porosity and semi-confined models. Some data suggest localised linear flow near pumped well. Heterogeneity in fracture distribution results in a complex response to pumping. Celtain broadly-defined zones and groundwater flow conditions are discernible within this heterogeneity.

Keywords

Groundwater, Fractured Aquifers, Hard Rock Terrain, Pumping Test, Kerala.

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J. P. Kukillaya ¹, K. Padmanabhan ², K. Radhakrishnan ²

Affiliations
1 TC 5/1184(2), 'Chandrika Vilas' Survey School Road, Peroorkada PO, Trivandrum - 695005, IN
2 Hydrogeologists, Kelala Samuhya Jalasechana Samithi, Thrissur, Kerala, IN

Abstract

Brackish groundwater occurs in fractured hard rock aquifers along a narrow N-S fracture zone in Puzhakkal-Avanur area which is more than 17 km from the sea. Relative propoition of chloride and bicarbonate suggests intrusion of saline water into this fracture zone from low lying areas connected to saline backwaters. Pumping test data and variations in intensity of fracturing suggest similarity to discontinuous fracture network model. The possible causes for spatial and temporal changes in electrical conductivity of groundwater are discussed. Present studies indicate overflow of blackish groundwater from the semi confined aquifers through bores in some dug-cum-borewells of the area.

Keywords

Groundwater, Fracture Aquifers, Hard Rock Terrain, Brackish Water, Spatial and Temporal Variations, Thrissur, Kerala.

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