1. Presented By Dr. Bhavana Umrikar Department of Geology SAVITRIBAI PHULE PUNE UNIVERSITY INDIA WATER WEEK: 2016 WATER FOR ALL: STRIVING TOGETHER

2. Introduction Subsurface hydrological and geological features play an important role in groundwater occurrence. One can generalize the occurrence of groundwater at shallow depth. But the behavior of deeper aquifers still remains a mystery in Deccan Volcanic Province. The integration of 3D model and GIS has proven to be an efficient tool in groundwater aquifer studies

3. Objectives To prepare the hydrogeological framework of a multi-layered aquifer system based on GIS, and Perform the subsurface 3-D modelling of Shivganga River Basin from Western Ghats Study Area The Shivganaga river watershed (SW) located in South-western of Pune city. Encompasses an area of around 175 km 2 where the lava flows in the study area have been divided into Diveghat Formation that is exposed at the low lying areas and Purandargarh Formation covering higher elevations.

4. Hydrogeology of study area Basaltic lava flows occupy more than 95% of the study area thickness from 7 to 45 m and represented by massive unit at the bottom and vesicular unit at the top of the flow flows are separated from each other by marker bed known as ‘bole bed’. shallower zones down to the depth of 15 to 20 m bgl form the phreatic aquifer and the deep confined aquifers generally occur at the depth of 40 m bgl Alluvium occurs in areas along banks and flood plains of river

5. Methodology The procedure whereby GIS software and Rock-Works 15 is used to facilitate 3D geological and hydrogeological conceptualization and characterization, which has been used further to develop the aquifer model.

6. Results and Discussion The 6 main lithology types of the Shivganga basin are represented as vertically repeated sequences that have significant spatial variations in terms of their occurrence, thickness, connectivity and elevation of top and bottom of each layer. It is believed that the NNW-SSE trending lineaments (Powar and Patil, 1980; Widdowson and Mitchell, 1983) are the manifestation of underlying Dharwarian weak planes onto the Deccan basalts, which are now opening up in the form of deep-seated fractures.

7. The borehole lithostratigraphic data and geophysical data is used to establish the stratigraphic model. Unit 1 The Hard / massive basalt lies at a depth between 14 and 60 m, Resistivity over 70 ohm-m Unit 2 Hard and jointed basalt The jointed and fractured Basalt layers form a discontinuous confined aquifer in the region. Resistivity 30 to 70 ohm-m Unit 3 The weathered basalt upto 15 - 20 m act as an unconfined aquifer and being tapped by majority of the dug wells in the study area (Zambre 1983). Resistivity 20 to 45 ohm-m Unit 4 The alluvial soil is seen to be developed along the banks of Shivganga river with varying thickness. The thickness of it is increasing with the higher order streams. 15 ohm-m to 25 ohm-m Unit 5 Residual soil: The climate has controlled the degree of disintegration of the basaltic rocks. The thickness of soils is, therefore, varying at different places though it is derived from the same parent rock. The thickness of residual soil varies from a few centimetres to less than a meter in the present study area. Resistivity Upto 20 ohm-m

8. Conclusions Geological and hydrogeological database generated in this paper offers geomodelling and 3D hydrogeological modelling. Furthermore, this study illustrates the importance of 3-D subsurface modelling in a complex geology area including the unpredictable patterns of vesicularity, weathering and jointing with respect to their extent and thickness, also the degree and inter-connections. It is the view of the authors that a 3-D modeling approach is the most efficient way to capture the subsurface complexity of most geologic settings, which can lead, in the context of an integrated approach, to improve the hydrogeologic appraisals. Finally, the proposed 3D model has helped in conceptualizing the deeper aquifer system in the study area, and it would be used in future for modelling groundwater flow modelling and contaminant transport.

9. AKCNOWLEDGEMENT The authors are thankful to Head, Department of Environmental Sciences and Geology, S.P. Pune University for extending help to use the department laboratory for analytical and computing facilities. REFERENCE Bean JE, Turner CA, Hooper PR, Subbarao KV, Walsh JN. (1986): Stratigraphy, composition and form of Deccan Basalts, Western Ghats, India. Bull Volcano 48: pp 61–83. Kadam, A. K., Kale, S. S., Pande, N. N., Pawar, N., and Sankhua, R. (2012): Identifying potential rainwater harvesting sites of a semi-arid, basaltic region of western India, using SCS-CN method. Water Resources Management, 26(9), pp. 2537-2554. Kale VS, Gupta A (2001): Introduction to geomorphology. Orient Longman Ltd., Calcutta Kolm KE (1996): Conceptualization and characterization of groundwater systems using Geographic Information Systems, Eng Geol, 42: pp. 111–118. Krishnamurthy J, Kumar NV, Jayaraman V, Manivel M (1996): An approach to demarcate groundwater potential zones through remote sensing and a geographic information system. Int J Remote Sens 17:1867–1885 Environ Earth Science 123 Trabelsi F, Mammou A. B., Tarhouni J., G. Ranieri (2011): GIS-based subsurface databases and 3-D geological modeling as a tool for the set up of hydrogeological framework: Nabeul–Hammamet coastal aquifer case study (Northeast Tunisia). Environmental Earth Sci, DOI 10.1007/s12665-011-1416-y Turner AK (1989): The role of three-dimensional geographic information systems in subsurface characterization for hydrogeological applications. In: Raper JF (ed) Three Dimensional Applications in Geographic Information Systems. Taylor and Francis, London, pp 115–127 Turner AK (1991): Three-dimensional modeling with geoscientific information systems, Kluwer Academic Publishers, Dordrecht, pp 443 Zambre (1982): Hydrogeology of Shivganga river basin, unpublished thesis