STATE GROUND AND SURFACE WATER RESOURCES DATA CENTRE
Address : PUBLIC WORKS DEPARTMENT, GOVERNMENT OF TAMILNADU
Cheppakkam, Chennai - 600 005. Phone : 8548196,8548212
Email: cegwch@vsnl.net

GROUNDWATER ACT - BILL INTRODUCED IN ASSEMBLY

 
Mission:
Tamilnadu being an agrarian State much importance is giver for the exploitation of Groundwater for the development of agriculture as about 95% of surface water resources have been harnessed in the State. Tamilnadu is in the forefront in the development of groundwater and about 63% of Groundwater Potential is under utilisation by means of minor irrigation structures. 73% of the total area of the State is covered by crystalline formations and about 27% is covered by sedimentary formations, which occurs all along the coast. The Sedimentary formation are most suitable for the large scale development of Groundwater.

About Us:
This department concentrates mainly on the following fields.
1. WATERSHED STUDY.

In Order to know the inter-relationship between rainfall, run-off and infiltration, the various parameters like rainfall, evaporation, temperature, wind velocity are being observed in smaller water sheds by setting up 65 meteorological stations in almost all the river basin, 15 water sheds in different type of soil characteristics have been selected for the study.

2. MONITORING OF WATER LEVELS.

Since Groundwater is a dynamic resource, continuous monitoring of water level is essential which helps to assess the gravity of the situation during adverse seasonal condition like drought. For this purpose, about 1748 wells including 618 drought wells spread over the State are under observation during the first week of every month. In addition to the open wells, 102 Nos.of automatic water level recorders are installed in some of the bore wells for continuous monitoring. Under Hydrology Project with World Bank assistance 730 piezometers have been installed andWater Level is being monitored by DWLRs.

3. WATER QUALITY STUDY.

About 6250 water samples are collected from various sources like shallow observation wells, bore wells, surface water samples etc. are tested for the suitability of domestic, agriculture and industrial purposes. For carrying out the above study, four Labs were established at Chennai, Madurai, Thanjavur and Pollachi in the State Ground & Surface Water Resources Data Centre. A charge of Rs. 90/- is being collected for the analysis of samples for the general Public and other user departments.

4. CONSULTANCY SERVICES.

This department renders consultancy service to farmers, general public and Government departments for the selection of suitable sites for digging wells, drilling bore wells based on the geological and geophysical survey. The consultancy services are offered at nominal rate of Rs.1000/- (as per GO Ms.No.1415/PW(R2) dt.1.10.93) for the selection of a favourable point.

Similarly consultancy services have been taken up for electrical logging in a bore hole and for giving suitable guidelines for the construction of bore holes. The charge for this work is Rs.2000/- (GO Ms.No. Ms.No.1415/PW(R2) dt.1.10.93).
 

5. COLLECTION OF RAINFALL DATA.

Rainfall data are being collected from 400 rain gauge stations throughout the State of Tamilnadu. Based on the data collected the maximum and minimum rainfall with percentage deviation are being worked out. The Histograms are drawn based on the 70 years rainfall data. The Isohyetal maps are being prepared to demonstrate the rainfall pattern in the District.

6. INTENSIVE SURVEY IN DARK AND GRAY AREA BLOCKS.

Based on the norms issued by the Groundwater Estimation Committee set up by the Government of India. Intensive survey was taken up and the Groundwater assessment was made for all the blocks in Tamilnadu.

In areas where the Groundwater development is below 65% the area was classified as white.

The areas where the Groundwater Development is between 65 and 85% is categorised as Gray. The areas where the Groundwater development is between 85 and 100% is categorised as dark.

Based on the above assessment in the year 1992, 89 blocks are classified as Dark. 86 blocks are classified as Gray. 209 blocks are classified as white. It was felt that there may be further scope for Groundwater development in favourable pockets of dark and gray area blocks also.

Subsequently the Groundwater Resources Estimation Committee in October 1997 has revised the Groundwater Estimation Committee Norms(1984) and accordingly modified the cateogorisation of blocks based on Groundwater development. In the revised norms, it is suggested that where Groundwater Development is lesser than 70% of the annual recharge the area has been classified as "safe" area.
Where the Groundwater development is greater than 70% but less than 90% is categorised as "Semi Critical" area. Where the Groundwater development is greater than 90% but less than 100% is classified as "critical" area.

Where the Groundwater development is greater than 100% of annual recharge is categorised as "over-exploited" area.

7. SALT WATER /FRESH WATER INTERFACE STUDIES.

In Tamilnadu the length of the coastal stretch is about 920 km.The entire stretch has been taken up to find out the salt water- fresh water interface studies. Minjur well fields which is located north of Chennai City where the salt water fresh water interface studies conducted during 1972 was located 3.5Km from sea coast,during 1997 this has moved to about 7.5 Km from sea coast. This has been confirmed by water quality studies.

8.DRILLING OF EXPLORATORY BORE WELLS.

As a part of investigation programme exploratory bore holes are drilled for the following objectives:-

(1) To explore the sub-surface lithological characteristics.
(2) To arrive at the sub-surface hydrogeological parameters.
(3) To find out the quality of Groundwater at different aquifers.

An annual target of 140 Nos. of exploratory bore wells have been fixed and it is being drilled in hard rock and sedimentary area in the entire state.

9. STUDY ON POLLUTION DUE TO INDUSTRIAL EFFLUENTS AND FERTILIZER IMPACT.

Many of the industries are located on the River Banks and their effluent discharge are let out into the river beds with or without treatment.

In order to determine the type, cause and extent of pollution of Groundwater due to industrial effluents studies are being carried out in 8 zones on various river basins and 4 locations have been selected for Fertilizer Impact Study on Groundwater.

10. FIXING SPACING NORMS IN GENERAL AND FOR RIVER COURSES.

The Commercial Banks are launching Minor Irrigation schemes and Lift Irrigation schemes. Under Lift Irrigation schemes wells are being sunk near the river courses and water is lifted and conveyed to far away places for irrigation. It has been decided to fix spacing criteria for sinking wells, all along the river courses. Necessary studies have been undertaken in 10 locations in different basins and the studies are under progress.

11. COLLECTION OF DATA ON GROUNDWATER STRUCTURES.

To assess the Groundwater potential, well structures are very much essential for the realistic assessment of Groundwater draft. The above study has been taken up and it has been proposed to collect the village wise well census data from the Village Administrative Officers and test check them by actual field verification. The target has been fixed as 46