क� द्र�यू�म भ जल बोड셍 जल संसाधन, नद� �वकास और गंगा संर�ण मंत्रालय भारत सरकार Central Ground Water Board Ministry of Water Resources, River Development and Ganga Rejuvenation Government of India AQUIFER MAPPING REPORT Parts of East Garo Hills and South Garo Hills District, Meghalaya उ�र� पूव� �ेत्र, गुवाहाट� North Eastern Region, Guwahati Govt. of India Ministry Of Water Resources, River Development & Ganga Rejuvenation Central Ground Water Board AQUIFER MAPPING IN PARTS OF EAST GARO HILLS AND SOUTH GARO HILLS DISTRICTS, MEGHALAYA January 2016 1 CONTENTS Page No. 1. INTRODUCTION 2. MAJOR GROUNDWATER RELATED ISSUES 3. MANIFESTATION AND REASONS OF ISSUES 4. AQUIFER GEOMETRY AND CHARACTERIZATION 5. AQUIFER MANAGEMENT PLAN 12 point data table Maps 23-46 Map 1 Location map Map 2 Base map Map 3 Soil map Map 4 Land use map Map 5 Isohyet map Map 6 Drainage map Map 7 FCC map Map 8 DEM map Map 9 Geological map Map 10 Geophysical map Map 11 Hydrogeological map Map 12 Location of Exploratory Well map Map 13 Value of Transmissivity in GW map Map 14 Value of Sp. Capacity in GW map Map 15 Location of Spring map Map 16 Spring discharge map Map 17 Depth to water level map (Pre-monsoon), Shallow aquifer Map 18 Depth to water level map (Post-monsoon), Shallow aquifer Map 19 Bore hole logs showing disposition of aquifer Map 20 Bore hole disposition Map 21 Distribution of pH in ground water Map 22 Distribution of EC in ground water Map 23 Distribution of TH in ground water Map 24 Distribution of Fe in ground water ANNEXURE 47-71 Table 1: Litholog Table 2: Aquifer Parameters 2 Table 3: Aquifer wise water quality data Table 4: Minor Irrigation Data Table 5 Minor, Medium and Bigger Minor Irrigation Data Table 6 Water conservation structures Table 7 Soil conservation structures Table 8 Cropping pattern data Table 9 Hydrological data Table 10 Water Level Monitoring Data Table 11 Rainfall data Table 12 VES/TEM Data Table 13 Spring data FIELD PHOTOGRAPHS 72 3 AQUIFER MAPPING IN PARTS OF EAST GARO HILLS AND SOUTH GARO HILLS DISTRICTS, MEGHLAYA 1. Introduction: The study area spread over 627 km2 falling under Survey of India Toposheet No. 78K/10 lying between North latitudes 25 30' to 25 45' and East longitudes 90 30' to 90 45' was covered as per the Annual Action Plan 2012-13. Its forms the central part of the Shillong Plateau and falls in East Garo Hills and South Garo Hills districts of Meghalaya state. Apart from Williamnagar, which is the district headquarters of East Garo Hills District, Songsak, Samanda and Dobu are some of the important localities of the area. The study area covers parts of three CD Blocks namely, Songsak (56.3 %), Samanda (32.8 %) and Dambo-Rongjeng (23.1 %) blocks of the East Garo Hills district, and a very small area of Baghmara CD Blocks (3.1 %) of South Garo Hills district. The total population of the East Garo Hills district are as per 2011 census is 3,17,618. Total number of habitants in the study area are about 76, 494. Physiographically the area can be described as highly dissected curvilinear/rectilinear hill ranges separated by valleys. The highest elevation is 688 m above msl at Misakokdok in west central part and the lowest elevation is 100 m above msl along Damringriver in north west. The country slopes towards both north and south from the central highlands. The area is mainly drained by the Simsang River, which flows towards southwest, Damring and Dudhnoi towards northeast and Rongre towards northwest with fairly straight courses. Rongre River flows cutting across the general trend of the rocks. The area shows an immature topography with high drainage density. The drainage pattern varies from dendritic type to rectangular to trellis pattern in lower orders. The geomorphological pattern indicates limited lithological and structural control. Geologically, the area is underlain by rock units belonging to Older Metamorphics represented by amphibolite, banded magnetite quartzite (BMQ) and calc granulite of Archaean to Palaeoproterozoic age and Assam-Meghalaya Gneissic Complex represented by augen gneiss, granite gneiss and migmatite of Archaean to Proterozoic age. These rocks are in turn intruded by Neoprotozoic to lower Palaeozoic age granite and porphyritic granite of Mylliem Granite and Sylhet trap of Jurassic to Cretaceous age. The Gneissic Complex and intrusive Mylliem Granite together provide the basement for the deposition of Palaeocene to Eocene sediments of Jaintia Group (represented by lower Shella Formation and upper Kopili Formation) and Eocene to Oligocene sediments of Simsang 4 Formation. The general trend of gneissic group of rocks is NE-SW to N-S with bedding parallel or by sub-parallel to gneissosity, dipping at low to moderate angles due SE. Khoksi fault is the main fault running NE-SW along Rimding Nadi. Depth of weathered zone in general, as deciphered from the Exploratory drilling data ranges between 7.0 to 13.0 metres. 5 2. MAJOR GROUNDWATER ISSUES IN THE AREA Approach to most parts of the area was main constraint due to prevailing atmosphere and heavy rains during June to September. Major part of the 627 Km2 area identified for aquifer mapping is occupied by forest cover. The area is sparsely populated and have no irrigation facility available. No Tube well / bore well /irrigation wells exist in the entire area As per Ground Water Exploration, higher concentration of iron is reported in groundwater where the depth of the well ranges from 113 to 202 m bgl. During lean period, people in places such as Wiliamnagar, Songsak and Samanda suffer from water shortage. 3. MANIFESTATION AND REASONS OF ISSUES In the study area depth to water level ranges from 0.11 to 2.50 m bgl during post- monsoon and water level ranges from 0.20 to 5.10 m bgl during pre-monsoon. In major part of the study area seasonal fluctuation varies from 0.18 m at Dawachipit to 2.79 m at Samanda-Megapagre. The climate of the district is largely controlled by South–West monsoon and seasonal winds. The East Garo Hills district being relatively lower in altitude to the rest of Khasi hills, experiences a fairly high temperature for most part of the year. The climate shows a variation from the warm, humid tropical in the plain and temperate climate is experienced in the hilly areas. The climatic conditions vary substantially from place to place due to wide differences in altitude. The study area has an average annual rainfall of 2606 mm. Bulk of the precipitation occurs between April and October, with July accounting for the maximum rainfall of the year. Between January and March, non-monsoon precipitation contributes about 22% of the total annual rainfall. 6 7 In the study area about 47 % of the area is cover by forest, fallow land account for 9.65 % , net sown area is 8719 ha. Details are as follows: SI District Study Forest Fallow Net Area Total cropped No. area area land Sown area (in Ha) (in Ha) (in Ha) (in Ha) (in Ha) 1 East Garo 61400 29372 5930 8719 (14.2%) 9992 (16.3%) Hills (47%) (9.65) 2 South Garo 1300 Not approachable / forest area Hills Total area 62700 8 There are no major or medium irrigation schemes in the study area. The major source of irrigation is rainfall. However, minor irrigation schemes involving flow and lift irrigation schemes are in vogue in the area. Flow irrigation involves diverting streams and rivulets and irrigating the fields by gravity. In the lift irrigation schemes, water is lifted from the rivulets or streams at convenient places to irrigate the fields in the adjoining areas. Irrigation through ground water is not yet practiced. Not a single irrigation well could be traced in the entire study area during the course of present study. Details of irrigation statistics in the study area is given below: SI District Study Command Cultivable Net Potential Potential No. area area area irrigated created Utilized (in Ha) (in Ha) (in Ha) area (in Ha) (in Ha) (in Ha) 1 East Garo 61400 1023 938 904 938 904 Hills (1.66%) (1.53 %) (1.47%) (1.52%) (1.47%) 2 South Garo 1300 Not approachable / forest area Hills Total area 62700 To know the water quality of the study area, water sampling done from both shallow and deeper aquifers. Water samples were collected during the study were analyzed for the different chemical constituents at the Regional chemical laboratory of CGWB, NER Guwahati and result are as given in table-12 format. The pH of the Ground water varies from 6.77 to 8.4 indicating slightly basic character of the water. The EC in water samples in the study are range from 84.4 to 402 micro Siemens/cm at 250C. The total hardness in the water sample ranges from 20 to 144 mg/l. In the study area, higher concentration of iron is reported in the deeper aquifer where the depth of the well ranges from 113m bgl to 200 m bgl. The concentration of Iron in this exploratory wells ranges from 1.12 mg/l to 2.75 mg/l. The concentration of Iron in Shallow aquifer/ dug well is within permissible limit. Table: Summary of chemical analysis data showing concentration of iron in deeper bore wells Result of Water samples from deeper bore wells Sl. no Fe (mg/l) No. of % of samples Depth of the Well samples 01 0-0—0.3 1 17 104.7 02 0.3---1.00 1 17 75.35 03 >1.00 4 66 113.80 to 202.30 9 It can be seen that higher concentration of iron beyond permissible limit is reported in the deeper aquifer where the depth of the well ranges from 113m bgl to 202.30 m bgl.