AGRAR Case Study. Kolwan Valley Site, Pune District
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AGRAR Project Case Study Research Report AUGMENTING GROUNDWATER RESOURCES BY ARTIFICIAL RECHARGE Detailed case study of Kolwan valley, Mulshi taluka, Pune district, India Himanshu Kulkarni, Uma Badarayani, Vinit Phadnis and Richeldis Robb Advanced Center for Water Resources Development and Management Plot 4, Lenyadri society, Sus road, Pashan, Pune-411021, India Email: [email protected] Website: www.acwadam.org Bibliographic reference Front Cover: Main monitoring Kulkarni, H., Badarayani, U., Phadnis, V. and Robb R., 2005. Detailed case study of Kolwan valley, Mulshi taluka, site in Kolwan valley (check Pune district, Maharashtra. AGRAR Project, Final Case dam CD3) with a part of the Study Report. stilling well and an observation www.bgs.ac.uk/hydrogeology/agrar borehole. Funded by Co-ordinated by JULY 2005 TABLE OF CONTENTS Page no. Summary 1. Purpose 1 1.1 Organisation and staff 2 1.2 Role played by local communities 3 1.3 Structure of the report 4 2. Case of setting 5 2.1 Introduction 5 2.2 District-scale setting 8 2.2.1 Pune district 12 2.2.2 Mulshi taluka 15 2.3 Kolwan valley 18 2.3.1 Topography and drainage 21 2.3.2 Climate 21 2.3.3 Rainfall 23 2.3.4 Soil type 25 2.3.5 Geology 27 2.3.6 Socio-economic profile and interventions through 30 watershed development projects 2.4 Watershed scale setting 34 2.4.1 Physical setting 34 2.4.2 Socio-economic setting 40 2.5 Recharge structure 46 3. Methodology 48 3.1 Introduction 48 3.2 Base line physical surveys, monitoring and groundwater 49 modeling 3.2.1 Baseline physical surveys 49 3.2.2 Hydrological monitoring infrastructure and 53 protocol 3.3 Socio-economic evaluation 72 3.3.1 Management and institutional arrangements 73 3.3.2 Water and livelihood surveys 74 3.3.3 Impact assessment 75 4. Results: Physical aspects 77 4.1 Introduction 77 4.2 Recharge site: Check dam CD3 78 4.2.1 Geology 80 4.2.2 Pumping test results 85 4.2.3 Check dams and hydrological time series data 87 4.2.4 Water balance for CD3 123 4.2.5 Water balance for structures CD1 and CD2 131 4.3 Watershed scale results 139 4.3.1 Chikhalgaon watershed 139 4.3.2 Other watersheds 143 4.4 Satellite sites and river basins 145 4.4.1 Rainfall data 145 4.4.2 Evaporation 147 4.4.3 Groundwater 150 4.4.4 Water balance 155 4.5 Hydrochemical characteristics 157 4.5.1 Water types and physiochemical characteristics 159 4.5.2 Major and minor elements 161 4.5.3 Geochemical controls 162 4.5.4 Regional characteristics 167 4.5.5 Water quality and depth 168 4.5.6 Hydrochemistry of recharge water 168 4.5.7 Pollution indicators 168 4.6 Comparison of results from recharge sites 169 5. Results: Socio-economic aspects 170 5.1 Patterns of water use 170 5.1.1 Drinking water and domestic use 170 5.1.2 Irrigation 172 5.1.3 Water for livestock and other uses 174 5.2 Management and Institutional arrangements 174 5.3 Water and livelihood analysis 176 5.3.1 Changes in resource conditions 176 5.3.2 Changes in access to and use of groundwater 177 5.3.3 Changes in livelihood ‘Outcomes’ 181 5.4 Impact assessment 183 5.4.1 Social change 183 5.4.2 Economic improvement 186 5.4.3 Benefits to livestock 187 5.4.4 Changes in cropping pattern 187 5.4.5 Other benefits 190 5.4.6 Other impacts 192 Annexure 1. Summary of findings on irrigated agriculture in 193 Chikhalgaon village 6. Discussion 209 6.1 Physical effectiveness of recharge structures 209 6.1.1 Natural and artificial recharge 210 6.1.2 Spatial and temporal influence of artificial 213 recharge 6.1.3 Scale and variability 215 Artificial recharge and livelihoods 216 6.2.1 Limitations in attributing causality to impact on 216 livelihoods 6.2.2 Groundwater dependent activities 218 6.3 Management and institutional arrangements 220 6.4 Sustainability of benefits 221 7. Conclusions and recommendations 224 7.1 Impact of recharge activities as a part of watershed 224 development 7.2 Overall lessons: Planning, design implementation and 225 management of artificial recharge 7.3 Strengthening positive outcomes and mitigating negative 226 impacts 7.4 Learnings: expected and unexpected results 227 7.5 Wider lessons 228 7.6 Future work 228 Summary This report is the final output describing results of the research conducted under the DFID funded AGRAR project in one of the three detailed case study sites, i.e. at the Kolwan valley site in Pune district of Maharashtra state in India. Research activities at the site began in mid-2003, although work, in the form of collecting background information, selecting areas for detailed surveys and setting up some of the research activities actually began in late 2002. The detailed background to the project was provided in the form of an ‘inception report’ (Kulkarni et al, 2003). The AGRAR research in Kolwan valley was undertaken by Advanced Center for Water Resources Development and Management (ACWADAM), a Pune based research NGO, in collaboration with GOMUKH, again based in Pune but implementing watershed development projects in and around Pune. The research essentially focused on studying artificial recharge to augment the groundwater resources through watershed development. It included the study of small check dams constructed across streams to create water impoundments, from which infiltration occurs over a period of time and which, in turn, is supposed to result in recharge to underlying aquifers. The study, therefore, involved meteorology, hydrology, hydrogeology, social and economic aspects of groundwater resources in Kolwan valley. An important criterion of the study was to understand if and how artificial recharge impacts on already changing livelihoods in such areas, where watershed development is being conducted progressively on a large scale, encompassing villages within a small river basin, called the Walki river basin (popularly known as the Kolwan valley). The AGRAR study focused on two basic aspects: 1. The physical dynamics of how recharge occurs. 2. The effects (if any) of artificial recharge on the livelihoods of communities living in the valley. The physical aspects of artificial recharge were studied using a comprehensive methodology that involved detailed monitoring of various aspects like rainfall, evaporation, stream flows, water levels in wells and observation boreholes around the main structures (check dams), aquifer properties (through pumping tests) etc. The socio- economic and livelihoods angle was studied using a combination of formal household surveys as well as informal discussions with various stakeholders. The methodology of monitoring was based on a standard process presented in detail as a set of guidelines for the project (Gale et al, 2003). Kolwan valley is located in Mulshi taluka (tehsil) of Pune district in Maharashtra and forms a part of the Deccan Volcanic Province of central-west India. Rugged, undulating landscape, with a variable soil cover and a high but variable rainfall characterise the area on the scale of the river basin. Constituted of different sub- horizontal basalt units that make up 8 lava flows, the Kolwan valley is dominantly constituted of ‘compound’ type of basalt units alternating with ‘compact’ basalt units. The degree of weathering and the nature and intensity of fracturing in these two units largely control groundwater resources within this area, with the compound basalt units showing sheet joints the density and frequency of which changes from place to place. The compact basalts, on the other hand are more sub-vertically jointed. A compound basalt unit and the underlying compact basalt unit are often in hydraulic continuity with each other, forming a well bounded shallow, unconfined aquifer over which check dams for facilitating artificial recharge are constructed. GOMUKH undertook watershed development in Chikhalgaon watershed in 1997-98; this watershed formed the major focus of the AGRAR study. Amongst a variety of watershed development measures, three check dams were constructed in a sequence to impound runoff through the mainstream and recharge groundwater in this watershed. The AGRAR study revealed that rainfall, runoff and recharge events around check dams are complexly interlinked, in an area where groundwater abstraction is limited. Natural recharge often masks effects of artificial recharge from such small structures, which occurs as a sequence of events from an individual structure. The quantity of recharged water (both natural and artificial recharge) is quite small in proportion to rainfall and surface runoff. Natural infiltration is to the extent of 100 mm, whereas infiltration from the artificial recharge structure is 33 mm. However, only some 12 mm of water is actually recharged to the underlying aquifer. As compared to this value, runoff estimates in watersheds from the Kolwan valley are in the range of 800 to 900 mm. Moreover, artificial recharge is more likely to occur through structures that are located on or within natural recharge areas (like the check dam CD3 in Chikhalgaon). Structures like CD1 and CD2 in Chikhalgaon actually gain water from groundwater discharges and have little to do with addition of water to the underlying aquifer(s). Nevertheless, the small quantities of water added to the aquifer as artificial recharge are large enough, when compared with the drinking water demand of different villages in the valley. On slightly larger scales, at the watershed or river basin levels, check dams have induced infiltration in such a way that baseflows to streams and river lag more than before, creating a positive impact on ‘environmental’ flows. At the same time, it is difficult to separate baseflow from the water releases from surface water tanks, especially in upstream areas of the main Walki river channel.