Ground Water Development

ARTIFICIAL RECHARGE TO GROUND WATER:

Artificial recharge to groundwater is a process of augmenting natural infiltration of rainwater or surface runoff into the subsurface aquifer through artificial means. It is a process by which the groundwater reservoir is augmented at rate exceeding the one under natural conditions of replenishment. Various methods and structures are suggested for artificial recharge to groundwater. The choice and effectiveness of any particular method & structure is governed by local hydrogeological conditions. Nature replenishes the groundwater resources by way of seasonal rainfall and infiltration through different geological formations. Present day scenario reveals that urbanization has drastically reduced the available land surfaces exposed for natural recharge in many areas. In order to maintain the hydrodynamic equilibrium between availability and utilization of the groundwater resource potential, along with the development of groundwater it is necessary to formulate Artificial Recharge to Ground Water through Rain Water Harvesting. This will also prevent the depletion of ground water level and balance the availability of ground water. However, hydrological conditions and sub-surface geo-structures of the area should be properly assessed to construct a suitable Artificial Recharge structures without which this process may aggravate further landslide specially in hilly areas

GROUND WATER DEVELOPMENT IN NAGALAND.

Ground Water is that water which is stored in the interstices (inter-particulate spaces) of the soil or rocks that forms the Earth. The soil or rock formation which contains water is called ground water aquifer. Below a certain depth in the underground, the earth is saturated in which all the free spaces or interstices are filled with water and the upper level of saturated zone is referred as ground water table which may be just below the ground level or may be hundred metres below ground level depending on the prevailing geo-hydrological condition of the area.

Ground water is precious natural resource for sustenance of life. It is a known fact that groundwater has played and will continue to play a key role in meeting the need of water in all sectors. It is widely distributed, dependable, can be developed and used with comparative ease and speed and can be tapped through simple underground structures/wells which can be individually or jointly owned.

In Nagaland ground water exploratory drilling was first carried out by the Central Ground Water Board, Ministry of Water Resources, Govt. of India during early seventies and thus sub-surface data so generated by CGWB formed the basis for further ground water development in the State. Later, in eighties, the DGM started ground water exploration in the state although it was confined to Dimapur valley area. Groundwater resources contributes major portion of water requirement in all sectors in Dimapur valley and it has greatly facilitated the social progress and developmental activities including agriculture productivities in the valley. The Department has also generated substantial amount of subsurface geo-hydrological data for guidance as well as provided technical know-how to the people for sustainable development of groundwater. In valley area the aquifer are represented by sand, gravel, pebble and, boulder zones of various thickness. Ground water occurs both in unconfined and confined condition in valley areas with a discharge ranging from 15000 to 25000 ltrs per hr and the water level ranges from 3 m to 15 m bgl.

Although the need for sustainable development and utilization of groundwater resources in hilly area was felt necessary, it has taken considerable time to come out with concrete assessment due to complex geological set-up of the state and other logistic constraints which remained unexplored till recently. From 10^th Five Year Plan onward, the Department has intensified ground water exploration in hilly terrain of the state and has established the availability of this vital resource to meet the need of water in hilly areas.

Ground water in the hilly area is manifested in the form of springs. Potential hydro-fractures so far identified for harnessing ground water in hilly areas includes, sheared zones, faults, joints and fractures. The successful development of ground water depends on proper identification of these secondary aquifers, their attitudes as well as application of suitable technology and deployment of appropriate water well drilling rigs. In hilly area ground water bearing geo-structure exists within 60m

below ground level with the yield/discharge ranging from 3500 to 6000 ltrs/hr. Water level ranges from 4m to 25m bgl except in few locations which exists below 45m below ground level. The analytical result of few ground water samples indicate presences of iron in most of the wells which needs little treatment before use

Ground water extraction being another form of underground Mining is absolutely necessary to be developed in a scientific way and adopt regulatory system depending on the prevailing sub-surface geo-hydrological conditions of the area. Therefore, the key issue for need based and sustainable development of groundwater resources in hilly area is, “its scientific management and regulation”. Sustainable and effective management of groundwater needs proper assessment of the available resources and understanding the changes in ground water system as well as its inter-connection with surface water. The evaluation of this resources involves a multi-disciplinary approach consisting of geo-hydrological, hydro-meteorological and hydrological studies and ultimately to arrive at a balancing exploitation in terms of quantity and quality with increasing demand of water and land use. Proper allocation of this vital resources amongst the different users/stakeholders must be insured with insight vision for prevention of any likely adverse effect in near future.

Groundwater is becoming an important water resources and being available in time and space, the pace of development of groundwater in the state has increased very fast particularly in the hilly areas to cater the need of water for various sector. However, unplanned and uncontrolled extraction of this vital resource will disturb the hydrological balance leading to over exploitation and seriously affecting the socio-economic conditions of the state. Therefore, the available groundwater in the state particularly in hilly areas must be developed judiciously and conserved at the same time for future use.