CHAPTER 4.1.9 GROUND WATER RESOURCES VELLORE DISTRICT 1 INDEX CHAPTER PAGE NO. INTRODUCTION 3 VELLORE DISTRICT – ADMINISTRATIVE SETUP 3 1. HYDROGEOLOGY 3-7 2. GROUND WATER REGIME MONITORING 8-15 3. DYNAMIC GROUND WATER RESOURCES 15-24 4. GROUND WATER QUALITY ISSUES 24-25 5. GROUND WATER ISSUES AND CHALLENGES 25-26 6. GROUND WATER MANAGEMENT AND REGULATION 26-32 7. TOOLS AND METHODS 32-33 8. PERFORMANCE INDICATORS 33-36 9. REFORMS UNDERTAKEN/ BEING UNDERTAKEN / PROPOSED IF ANY 10. ROAD MAPS OF ACTIVITIES/TASKS PROPOSED FOR BETTER GOVERNANCE WITH TIMELINES AND AGENCIES RESPONSIBLE FOR EACH ACTIVITY 2 GROUND WATER REPORT OF VELLORE DISTRICT INRODUCTION : In Tamil Nadu, the surface water resources are fully utilized by various stake holders. The demand of water is increasing day by day. So, groundwater resources play a vital role for additional demand by farmers and Industries and domestic usage leads to rapid development of groundwater. About 63% of available groundwater resources are now being used. However, the development is not uniform all over the State, and in certain districts of Tamil Nadu, intensive groundwater development had led to declining water levels, increasing trend of Over Exploited and Critical Firkas, saline water intrusion, etc. ADMINISTRATIVE SET UP Vellore district, a newly formed district was carved out from the erstwhile North Arcot district during 1988-89.the Total geographical extent is 5, 92,018 hectares (5920.18 sq.km.) and is sandwiched between the following coordinates. Latitude : 12⁰15’23” - 13⁰12’32” Longitude : 78⁰24’16” - 79⁰54’56” The population as per 1991 census, is estimated around 30, 26,432 of which 20, 66,718 are in rural areas and 9, 59,714 are in urban centers respectively. A somewhat belted pattern of settlement is discernible in correlation with relief, soil, rainfall, topography etc., which gives rise to either compact blocks of population or linear pattern along the river courses and arterial roads. This district exemplifies in the development of rail and road transport systems by linking all major cities and towns both inside and outside the State. Vellore District is totally bifurcated into 53 Firkas. 3 1. hydrogelogy (i) Major Geological formations: Geology: Geologically, the entire district is broadly classified into hard rock and sedimentary formations. a) Hard rock More than 90% of the area in this district is underlain by these formations. These hard rock formations are the oldest rocks of the earth’s crust and exhibit similar characters. They are Azoic, Crystalline and extremely contorted. The most common types of hard rock formations are the Gneisses and Charnockites. The Gneissic formations are found in almost all the taluks of the district but lack uniformly both in composition and texture. Different names are attributed to the Gneissic formation based on its mineral content. Charnockite formations occur as distinct pockets in Javadu hills, Amirthi Reserved forest etc., i.e., on the Southern and south western parts of the district. Quartzites and Doleritic Dykes which are intrusive bodies and resistant to weathering, are seen as patches among Charnockite and Gneissic formations. Tectonically and structurally the area is traversed by minor regional faults and fissures. The regional faults of Javadi Hills are of considerable length. b) Sedimentary formations The sedimentary or the Quarternary Alluvial deposits which are the transported sediments by the river and streams stretch mainly along the Palar river course as thin isolated patches. These formations overlie the Hard rock formation. Drilling bore holes: In vellore district, more than 144 bore wells have been drilled by the State Ground and Surface Water Resources Data Centre of Public Works Department to ascertain the sub surface condition. Generally in hard rock areas, discontinuous and heterogeneous nature of weathered formation influences the occurrence and movement 4 of groundwater and in turn is favoured by fissures and joints towards certain restricted directions. The thickness of top soil, weathered zone, jointed zone and depth of occurrence of fresh rock varies moderately to widely throughout the district. In Tiruppathurtaluk, considerable thickness of weathering ranging from 15.00 to 36.00 mts. In Gudiyatham and Vellore taluks the weathering extends upto 30.00 mts. and 20.00 mts respectively. In the remaining parts of the district, the thickness of weathering ranges from 11.00 mts to 20.00 mts below ground level. Aquifer parameters Aquifer is a geologic formation or stratum containing water in its voids yielding significant quantities of water to a well or spring. a) Hard rock In hard rock areas of this district, the thickness of aquifer varies between 2.00 And 36 mts. below ground level. Deep weathering 9in gneissic rocks depends upon the mineralogical contents and fracture development. The range of aquifer parameters are as follows: Range in hard rock formation S.No. Description Range 1. Well yield in LPM 40 - 200 Transmissivity (T) 2. 8 - 80 m2/day 3. Permeability (K) m/day 0.5-2.5 b) Alluvium The alluvium occurs along the Palar river course and the thickness of alluvial aquifer ranges from 10.00 mts to 12.00 mts. The range of aquifer parameters of alluvium are furnished below: 5 Range in Alluvial formation S.No. Parameters Range 1. Well yield in LPM 200-400 Transmissivity (T) 2. 200-300 m2/day 3. Permeability (K) m/day 20-30 Source: State Ground and Surface Water Resources Data Centre, Chennai-113. (iii) Drilling: The drilling types are different according to the formation of the terrain. In general, DTH rigs are used in Hard rock formations for drilling a borewell at a depth ranges from 30m to 200m, according to the extension of joints, fractures, lineaments, etc in an area. In Sedimentary formations, rotary rigs with different rotors used according to the Tube well’s diameter. The Bento novate clay is used in rotary rigs to avoid the collapse of the Tube well. The sedimentary tube wells are drilled up to a depth of 30m to 300m depending on the area, yield,etc. In alluvial formations, the hand rotary used for drilling tube wells ranges from 10m to 15m.In river beds, infiltration tube wells used for extraction of groundwater. In Hard rock, the well designing is simple. The upper top soil and highly weathered zone is cased with PVC pipe and the remaining weathered, Fissured, Jointed portion is left as it is. In Villupuram District, the weathered zone ranges from 1.0m to 12.0m. In Granitic gneiss area, the highly weathered portion will be more up to 15m but in charnockite area, the weathered zone will extend up to 8.0m to 10.m only. In Sedimentary area, the well construction depends on the occurrence of sand thickness in the referred area. The logger is also used in the construction to identify the area of good quality of water. 6 2. GROUNDWATER REGIME MONITORING: (i) Notes on existing water level scenario: The water level is being monitored by State Ground & Surface Water Resources Data Centre from 1971 onwards from a network of 1746 observation wells (shallow open wells) located all over the State. The water level readings are observed in the first week of every month by the field officers. In Vellore District, 158 observation wells and 111 piezometers,totally 269 wells are monitoring on Monthly basis. The Central Ground Water Board also monitors the water level from 900 numbers of wells spread all over the State. They observe water level four times in a year. ( i.e January, May, August and November). The collected water level data are uploaded in GWDES software and database is maintained regularly for analysing the water level trend with rainfall. From the Monitoring network of wells, the selected representative wells are taken for Resource Estimation computations. In Vellore District, during the pre monsoon, the water level generally in declining trend ranges from G.L. to 15m. The depth of well below GroundLevel 12.0m are become dry during hot season like May, June, July. In the post monsoon, the water level generally in upward trend due to rainfall and it may reach the Ground Level also. The water level trend maps for pre and post monsoons are included as Annexure- I & II. (ii) Long term trend of water level: The long term fluctuations of water levels range from G.L. to 14.0m in many parts of the Vellore District. The analysis reveals that the water level has gone down in the north, west and central parts of the Vellore District. The inference taken from the annual fluctuation is due to lack of rainfall which in turn affects the groundwater levels in phreatic aquifer. The seasonal fluctuation study reveals that due to necessity for development of ground water for different sectored needs and due to failure of monsoons, the water level has gone down. The hydrograph of observation wells water level trend from 2005 to 2017 enclosed as Annexure – III and water level trend from 2000 to 2017 of Piezometers enclosed as Annexure – IV for Vellore District. (iii) Existing network of Monitoring wells: In Vellore District, the existing network of monitoring wells is 269 7 wells, 158 wells are observation wells and 111 wells are piezometers. These wells are observed for every month water level. Vellore: Observation Wells - Location and Co-ordinates Block / Well No District Tahsil / Taluk Village Latitude Longitude Mandal 23011 Vellore Thiruppathur Kandili Chinrampatti 12°25'00" 78°35'15" 23011A Vellore Thiruppathur Kandili Chinrampatti 12°23'58" 78°33'36" 23018 Vellore Thiruppathur Natrampalli Katteri 12°35'00"