Distribution of aquifer characteristics in different geomorphologic units in a granitic terrain
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ORIGINAL ARTICLE
Distribution of aquifer characteristics in different geomorphologic units in a granitic terrain Ratnakar Dhakate1 Received: 30 April 2020 / Accepted: 2 October 2020 © The Author(s) 2020
Abstract Knowledge of aquifer characteristics is essential for groundwater development and management studies. Detailed hydrological studies were carried out in a granitic terrain consisting of different geomorphologic units to resolve the coverage, performance, and characteristics of the aquifer parameters through the application of the pumping test method. An interpretation was performed by different methods, viz., Theis, Jacob, Hantush, and Rushton and Redshaw (numerical finite difference method) to ascertain the aquifer parameters. These parameters are vital for future groundwater development and management studies. Transmissivity (T) values estimated by Theis method range from 3.83 to 436 m2/day; 3.77 to 718 m2/ day; and 16 to 160 m2/day, by Jacob method it ranges from 3.90 to 436 m2/day; 3.73 to 769 m2/day; and 17.3 to 152 m2/ day, by Hantush method it ranges from 1.63 to 189 m2/day; 0.53 to 755 m2/day; and 19.3 to 118 m2/day, while by numerical method it ranges from 3 to 455 m2/day, 3 to 700 m2/day, and 17 to 148 m2/day in pediplain with moderate weathering (PPM), pediplain with shallow weathering (PPS), and buried pediplain with shallow weathering (BPPS) geomorphologic units, respectively. Similarly, a radius of influences ranges from 9.75 to 1391.0 m; 8.0 to 698.09 m, and 380.78 to 433.76 m in PPS, PPM, and BPPS geomorphologic units, respectively. The aquifer parameters obtained by the pumping tests were correlated with the structural features and different geomorphologic units. It was found that these parameters have wide variations within each geomorphologic feature. The radius of influence of each test well was calculated and compared with the in situ measured discharge of various wells within the area. The high values of transmissivity (T) are attributed to aquifer controlled by fractured zone in the area. Keywords Geomorphology · Transmissivity (T) · Storativity (S) · Radius of influence and aquifer parameters
Introduction The hard rocks terrains such as granites are usually devoid of primary porosity. Secondary porosity was developed due to weathering and fracturing of the hard rock and forms a good aquifer zone for groundwater occurrence and movement. The occurrence and movement of groundwater in such formation mainly depend on factors like saturated thickness of the weathered zone, its intensity, areal extend, and interconnection of joints and fractures. In hard rock terrain, the yields of bore wells decrease with depth (Landers and Turk 1973). This is mainly due to a decrease in the degree of weathering and fracturing with depth. Thus, most of the groundwater * Ratnakar Dhakate [email protected] 1
CSIR-National Geophysical Research Institute, Uppal Road, Hyderabad, Telangana State 500007, India
circulation restricts to a shallow depth in the weathered and fractured zone. The optim
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