Micro-level Aquifer mapping & Aquifer management Plan for Cuddalore Coastal Aquifer system, Tamilnadu Dr. D.Gnanasundar, Dr. M.Senthilkumar & Sh. N. Rameshkumar Central Ground Water Board South Eastern Coastal Region, Chennai Ministry of Water Resources, River Development and Ganga Rejuvenation Government of India Regional & Micro-level aquifer mapping Aquifer Mapping Objectives: 1. To decipher the vertical & lateral extent of the is a scientific process wherein a Aquifer Disposition – (2D & 3D) along with their combination of Geologic, Geophysical, characterization. hydrogeological & Chemical studies 2. To formulate Aquifer Management Plans (Field & Laboratory studies) – applied to 3. To facilitate sustainable management of GW characterize resources at regional & local level through • the quantity, Participatory Groundwater Management. • quality & • sustainability of groundwater. Tamilnadu & UT of Puducherry Approach Regional Aquifer Micro-level Mapping aquifer mapping Decipher Aquifer Units within Principal Aquifers Conceptualization of the aquifer system Aquifer management Plan through Numerical Modelling Information on aquifers to farmers, State Govt. stakeholders for sustainable GW management Regional aquifer mapping Regional & Regional Aquifer System, Tamilnadu Micro-level aquifer mapping Pondicherry coastal aquifer Cuddalore coastal Aquifer Sandstone Alluvium sand Cuddalore coastal aquifer Alluvium sand sandstonesandstone Bay of Bengal Jayankondam aquifer Bay of Bengal Alluvium sand Alluvium sand Specific Issues Micro-level aquifer mapping 1. Coastal aquifer – forms a part of Cauvery Basin. 2. Intensively irrigated area by Groundwater 3. Depressurization of the aquifer for mining activity. 4. Groundwater is pumped for drinking water supply to Chennai city during lean periods. 5. Extension of the aquifers into the sea. Regional Aquifer Mapping & Aquifer management Plan : 1948 sq.km Aquifer Mapping Location : 200 km south of Chennai. Recharge zone (Cuddalore dt, TN) Micro-level Aq.mapping : 428 sq. km Sandstone Sandstone Alluvium Vellar river Perumal Eri Strike : North East – South west Dip : South East GW flow : South East (along the dip direction) 2 – D Aquifer Disposition Outcome by data gap analysis A” A north south (Aquifer 1/unconfined) Recent alluvium Sand/sandstones clay clay Cuddalore Sandstone – Mio-pliocene sandstones (Aquifer 2/Confined) potential aquifer lignite • Ferruginous, • Friable Eocene sandstones • Medium to coarse (Aquifer 3/Confined) grained with clay • continuous or discontinuous clay intercalations. Eocene sandstones (Aquifer 4/Confined) Pebble west Inference : Multi-layered aquifer system B East ? Inf. required 40 m B’ clay msl 40 m lignite clay 80 m clay lignite 100 m Lignite at 80 m bgl 120 m clay Open cast mine – Neyveli Outcome by data Gap analysis Hydrogeological studies Long term Piezometirc head behaviour of aquifer – II Piezometric head (m) Kudikadu PZ Exploration carried upto 400 bgl. Period in months 1. Exploratory Drilling were carried out at 18 locations & 2. Additional 22 Piezometers were constructed to Zone wells (Pz) tapping aquifer unit –III & IV micro-monitor the behavior of Groundwater Heads of Different Aquifer Units. Aquifer Disposition inferred from E-Log Outcome from geophysical study Principal Aquifer : Sandstone Aquifer Units : 4 nos Age: sangolikuppam Sst. Aquifer – I (Sand/Sandstone) clay Mio-pliocene Sst. Aquifer – II Inference : (Sandstone) Multi-layered aquifer system (down to explored depth of 400 m) clay Lignite (marker bed) Sst. Aquifer – III clay (Sandstone) Sst. clay Eocene Sst. Aquifer – IV (Sandstone) Outcome from exploratory drilling Aquifer Aquifer disposition inferred from Litholog Formation Units Recent - (exploratory drilling at Pachacharapalayam site) Alluvium 18 nos of additional exploratory wells were Aquifer I Aquifer - I drilled. Mio-pliocene (unconfined) CGWB Rig - Cuddalore (Gl – 73m bgl) sst. Mio-pliocene sandstone Clay Clay (Cuddalore formation) Aquifer -II Mio-pliocene Aquifer – II - Cuddalore (107 – 122 m bgl) (confined) sst. Eocene - lignite/CLay Lignite/clay (122 – 126 mbgl) Marker bed Principal aquifer (Sandstone) Aquifer - III Aquifer - III Eocene - Sandstone ) (126 – 244 mbgl) (Confined s Eocene Litholog at drilling site Clay Clay sandstone (Neyveli formation) Aquifer - IV (263 – 364 mbgl) Aquifer -IV Eocene - Inference : Sandstones (Confined) Multi-layered aquifer system (down to explored depth of 364 m) Outcome from Pz head analysis Pacharap alayam Piezometric Heads of Aquifer - III 40 Laterite Ayekuppam Kothandarajapuram 20 Aquif er -I SST Aquif 0 SST er -I msl Q= 10 lps -20 SST Bay of Bengal Aquif Clay Clay er -I -40 SST Aquif Aquif Clay discontinuous SST -60 er -II Q = 14 lps er -II Clay -80 Lignite/clay Lignite SST Clay -100 SST Lignite ?? Clay -120 SST Lignite Aquif Q = 29 lps SST -140 er -III Lignite SST -160 SST Aquif head in Pzmsl er – Aquif III er -III -180 -200 Clay -220 Q= 48 lps Clay -240 Inference: 1. The variation of Piezometic heads reaffirms the presence of 4 aquifer -260 SST Aquif units & its nature (unconfined/confined) within the principal aquifer. (Aq-1 – -280 er -IV unconfined, II, III & IV – Confined) -300 2. The Pz head (long tern hydrograph) infers distinct recharge & discharge -320 mechanisms in all 4 aquifer units. -340 3. Individual aquifer management plan for each aquifer unit is required. Outcome Micro-level aquifer mapping (Aquifer Information System) Less potential zones Aquifer – I (Unconfined) Aquifer – II (confined) Aquifer – III (confined) Aquifer –IV I (confined) Less potential zons Less potential zones Aquifer – I (Unconfined) Domestic & irrigation Aquifer – I (Unconfined) irrigation Aquifer – I (Unconfined) Industrial & irrigation Aquifer – I (Unconfined) Drinking water supply to chennai city To be shared to farmers, local administration for participatory GW management. 3 D Aquifer Disposition (Kurinjipadi Block), Cuddalore District, Tamilnadu Outcome Aquifer Unit – I (unconfined) west east Bay of Aquifer Unit – I (unconfined) Bengal Mio-pliocene sandstone Aquifer Unit – II (unconfined) Mio-pliocene sandstone Aquifer Unit – III (unconfined) Eocene sandstone Aquifer Unit – IV (confined) Eocene sandstone 0 m scale 300 m 0 km 10 km Pacharap alayam Outcome from hydrochemical studies 40 Laterite Ayekuppam Groundwater quality of all four aquifer units Kothandarajapuram 20 Aquif er -I SST Aquif 0 SST er -I msl -20 SST Bay of Bengal Clay EC : 250 µS/cm Clay Aquif -40 er -I SST Aquif SST unconfined er -II Aquif -60 EC : 120 µS/cm er -II Clay -80 Lignite/clay Lignite SST Clay -100 SST confined Lignite ?? Clay -120 SST Lignite Aquif EC : 550 µS/cm SST -140 er -III Lignite SST confined -160 SST Aquif er – Aquif III er -III -180 -200 Clay -220 EC : 1000 µS/cm Clay -240 -260 Inference: SST Aquif -280 er -IV 1. Again re-confirms the presence of four distinct -300 aquifer units 2. All the 4 aquifer units have potable GW (insitu -320 Brackish GW exists as pockets near coasts) -340 Regional Conceptualization Cuddalore Coastal Aquifer. Multi-layered aquifer system (Seven Layer model) Depth of Outcome of the Study Layer – 1 (sand/sandstone) Occurrence Layer – 2 (clay- discontinuous) 20 – 120 m Q (10 – 45 lps) Layer- 3 (Sandstone) Q (10 – 40 lps) Layer – 4 (Clay/lignite – discontinuous) Q (8 – 40 lps) Layer – 5 (Sandstone) 20 - 180 m Layer – 6 (Clay – discontinuous) Q (5 – 15 lps) Layer – 7 (Sandstone) 40 – 240 m Recent alluvium and sst... Abstraction for Domestic & Irrigation Mio-pliocene sandstone User aquifer for Irrigation. 40 – > 400 m Depressurization for mining activity Abstraction for drinking water Explored depth : 400 m supply to chennai city 0 km 31 km 72 km Numerical Modelling for Aquifer Management Plan: Model Grid, Boundary conditions & input parameters. 7 layer model Finer gird Total model area : 1948 sq. km. (250 m x 25 m) Variable head boundary (Ponnaiyar River) Total Cells : 34629 nos Columns and Rows : 51 and 97 Layers : 07 nos Coarser grid : 1000 x 1000 m Finer grid : 500 x 500 m (Grid pattern is based on the data availability & objective of the model) River flows during rainy season only - River (Ponnaiyar, Gadilam & Vellar) flows for 40 days in a year - No significant base flow to the river. Perumal eri/tank (10 km width & 3 Km wide) taken as General Head boundary Constant Head Boundary (Sea) Boundary Head Constant Coarser Grid 1000 m 1000x m ) ( (water in tank remains almost same throughout). GW Flow equation Variable head boundary (Vellar River) Hydraulic conductivity (Kx) values as input : K = 30 – 40 m/day Method : Finite Difference Method Specific Yield : 12 – 14 % (unconfined, Aquifer – I) (FDM) Storativity : 0.003 to 0.000093 ( confined aquifer II, III & IV) Recharge rate: 12 - 14 % of the annual recharge (1290 mm/yr). Outcome from numerical modelling studies Groundwater withdrawal from aquifer units (I,II,III & IV) from 1000 Cuddalore coastal aquifer system Cumulative effect of groundwater 800 withdrawal for irrigation, mining Total activity, drinking water supply & Pumpage domestic purpose (MCM/yr) 600 Total annual Groundwater withdrawal from all Aquifer Units : 1213.58 mcm 400 Pre-pumping For Irrigation Total annual pumping from Neyveli mine : 133.10 mcm 200 Mining activity 1950 1960 1970 1980 1990 2000 2010 Period in years Aquifer Hydrogeologic Unit Irrigation Industrial Domestic (GW withdrawal in mcm/yr) ---------------------------------------------------------------------------------------------------------------------------------------------- Sand/sandstone Upper Cuddalore (Aq-I)