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The Central Ground Water Board is the apex organisation for development and management of ground water resources of the country. It is entrusted with the responsibilities of scientific studies-including surveys, investigation and exploration programmes for the assessment of the resources-and assisting the states in development, management, augmentation, conservation and protection of ground water from pollution. It is also carrying out reappraisal ground water surveys, ground water exploitation, ground water resource assessment, monitoring of the behaviour of ground water system and water quality. Central Ground Water Board assists drought-affected states in locating sites and designing tube wells. Further the organisation studies the feasibility of application of new technologies for planning development and management of ground water resources. The activities of the Board, which are regular in nature, are being pursued on a continuing basis. Central Ground Water Board has a Regional office at Chennai for attending to work in Tamil Nadu and Union Territory of Pondicherry. It is headed by a Regional Director with Scientific Officers of various disciplines and supporting staff. The Region is responsible for Hydrogeological studies and ground water resource estimation by drilling. The Divisional office at Chennai is headed by Executive Engineer with supporting staff and is responsible for drilling and construction of wells under exploratory programme and also for drilling and construction of deposit wells as and when requests are received from State Governments. The Divisional office is under direct Administrative Control of Regional Director, South Eastern Coastal Region. The entire area of the State has been already covered by systematic Hydrogeological surveys. Also estimates for blockwise ground water potential is finalised with State GWD. In vies of the changing ground water scenario in terms of quantity and quality of water with time, the need for continuous evaluation of ground water regime was felt and the reappraisal surveys were started since 1980. The surveys are planned to update the data at every fine years. In addition to this, ground water regime studies are also carried out by establishing Hydrograph Network Stations distributed over the State. Initially the studies were started in 1969 and over the years the number of stations was increased. Presently there are 785 National Hydrograph Stations in Tamil Nadu and U.T. of Pondicherry. These stations are monitored four times in the year i.e. during January, May, August and November. Also there is a proposal to modernise the database under "Hydrology Project" with assistance from World Bank. One of the major objectives of the Hydrology Project is the construction of purpose-built wells for the standardisation of procedures for ground water monitoring data processing, storage and dissemination. The reappraisal surveys and ground water regime studies have clearly brought to light, the areas of over development and necessary remedial measure have been suggested for specific areas of study.
Ground water resource has two components-dynamic and static. Dynamic resource gets replenished every year but inputs to and outputs from ground water regime are changing with time. It is essential to reappraise the ground water situation periodically and assess the effects of development on ground water regime. Since development of resource leads to changes both in its regime and water quality, planning for further development of resource, therefore, needs to be based on effects of the developmental activities on ground water regime. Till now, CGWB has been taking up reappraisal ground water development programmes keeping in view the changing situations. But now, these surveys have to be renamed as "Integrated Ground Water Development & Management" studies to involve all other disciplines in field activities to make it more scientific, comprehensive and informative.
The drilling operations have enabled demarcation of aquifers both in lateral and vertical extension and evaluation of various aquifer parameters for designing of suitable structures and assessing their yield capabilities in various hydrogeological set-ups. These studies help in identifying areas worthy of further development. Ground water exploration has contributed to a very large extent in guiding the States to take up purposeful follow up action with regard to ground water development and its utilisation. Emphasis has been given to plan exploration on long-term basis and schemes have been prepared for the areas where exploration is proposed. As far as possible, contiguous and composite areas, hitherto unexplored, have been selected, keeping in view scientific requirements and also priorities of State Governments. Construction of piezometers has been taken up on a large scale based on the requirements of the Hydrology Project.
The Board has been constructing tube wells on deposit basis for Government Organisations and Undertakings. It has been decided to give priority to exploratory drilling programme and, therefore, very limited deposit well work is being undertaken.
Central Ground Water Board assists various user organisations in the country (Rural, Urban, Defence, Industrial Establishment) to serve their immediate water supply needs by selecting sites and areas for developing ground water supplies. In this effort it also extends the benefits of its expertise in the estimation of quantum of water supply against the projected demands. It is helping defence establishments, on priority basis, in the selection of sites for tube wells and solving related water supply problems.
The increasing diverse activities of modern society are putting a great stress on the ground water regime and its quality. Under such circumstances it is imperative that the ground water regime in different hydrogeological set-ups in the country is monitored regularly to assess changes in its quantity and quality. Central Ground Water Board has a countrywide permanent network of hydrograph stations. Water levels are monitored at these stations throughout the country four times every year, in the months of January, April/May, August and November respectively, simultaneously during a two-week period. A record of chemical quality of ground water is also maintained by collecting and analysing water samples once in the month of April/May every year. The data collected from such stations is utilised for analysing the ground water scenario and for preparing maps on water levels and chemical quality of ground water.
The Board proposes to intensify its efforts in the field of Geophysical studies. Special efforts would be made for conducting deep resistivity surveys for the exploration of deeper aquifers in both alluvial and hard rock areas. All the boreholes drilled by Central Ground Water Board are proposed to be logged for various geophysical parameters.
Chemical analysis of water samples collected during systematic and reappraisal surveys, exploratory drilling, pumping tests and monitoring of water quality through network of hydrograph stations are carried out and support is provided for other investigations and special studies in concerned Regional laboratories.
Results of investigations carried out by Central Ground Water Board are suitably documented in the form of reports and maps. These are categorised under three main heads viz. Survey Reports, District Reports and District Hydrogeological maps-on 1:250,000 scale. The results of investigations are also documented in the form of State Reports, Atlases and Maps. Preparation/revision of district reports based on Reappraisal Ground Water Survey has also been taken up.
In certain areas ground water development has reached a very high stage, which has created problems like declining ground water levels with consequent decline in water supply, failure of wells/tube wells, saline water encroachment, etc. It is in this context that the arid and semiarid regions and drought-prone areas require adoption of measures aimed at augmenting supply. The National Water Policy also lays particular emphasis on augmentation of ground water resource through various natural and artificial means. In tune with this policy, CGWB has taken up Artificial Recharge Studies.
The Central Ground Water Board and State Government Organisations are collecting data on various aspects of ground water resources investigation, development and management. The task of developing programmes involving a uniform standardisation format required for collection and handling of data with the use of computers and microprocessors has already been initiated in the Board and ground water level data of hydrograph network stations for all the states has been computerised. Further action would be taken to update and develop new programme for storage of additional data from states and newly established hydrograph network stations for quick retrieval. Data on water quality behaviour and other developmental aspects will also be stored.
The main objectives of the Hydrology Project are: 1. Updating of data collection infrastructure including observation well network, instrumentation and laboratory facilities. 2. To establish and integrate national and state ground water data banks. 3. Providing training facilities including the infrastructure for establishing the National Ground Water Training & Research Institute.
CGWB has been providing assistance to states under the programme of Rajiv Gandhi National Drinking Water Mission launched by the Ministry of Rural Areas & Employment, by diverting personnel from other ongoing activities of the Board. Under this, studies shall be undertaken through collection and analysis of data, photogeology, remote sensing and geophysical studies.
Programmes for enhancing awareness among general public regarding conservation, protection and regulation of ground water are being taken up in various states regularly. The objectives include: 1. On-farm conservation by adopting optimal cropping pattern, drip and
sprinkler irrigation systems, construction of furrows, basin borders, etc.
The Central Ground Water Board, South Eastern Coastal Region, has a Hydrometeorology & Hydrology Section with the following officers posted in it: Scientist-C (HM) - One The main activities of this section are: i. Collection of Meteorological data, mainly from IMD, with special emphasis
on rainfall (daily, monthly, seasonal and annual) for various raingauge stations
in Tamil Nadu and Pondicherry;
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