Impacts of Ground Water Depletion

Ground water is the water found under ground in the cracks and spaces in soil, sand and rock. It is stored in and moves slowly through geologic formations of soils, sand and rocks called aquifers. It is one of the Nation’s most important natural resources. It plays a major role in ensuring livelihood security across the world, especially in economies. Ground water contains mineral ions which slowly dissolved from soil particles, sediments and rocks named as dissolved solids. Continuous discharge of industrial effluents, domestic sewage, use of fertilizers and pesticides, waste dump and over exploitation of the resources have badly impact on ground water sustainability. Though over utilization of ground water is the key factor for ground water depletion but there are other factors which have negative impacts on ground water sustainability. The most important impact on ground water depletion is loss of base flow; other impact being severe crisis of safe drinking water and irrigated water.
Ground water is one of the extremely valuable renewable resources. Now a days pollution of ground water resources is a matter of serious concern. Ground water quality comprises the physical, chemical and biological qualities of water. Temperature, turbidity, color, taste and odor are the physical quality of water. pH, E.C, N,P,K ,organic carbon etc. represent the chemical quality and total microbiological count etc. stand for biological quality of ground water. Microbial components are also available in ground water. There are different forms where ground water is stored and human can withdrawal from there namely aquifers, wells etc. Manmade activities play a key role for depletion of natural composition of ground water through disposal or dissemination of toxic chemicals and microbial matter at the land surface and into soils, or through waste water. In India most of the population is dependent on groundwater as the only source of much clean drinking water supply than surface water. Sustainable ground water management is a burning challenge for the 21st century because it ensured livelihood security across the world. Agriculture dependent countries like India are most relied on ground water. Although ground water is mentioned as renewable resource but it does not recycle rapidly. The ground water recycling depends on aquifers depth, type, location and connectivity etc. Generally the average time of renewal of ground water is 1,400 years as per World water Balance, 1978. Significantly renewal rate of shallow ground water are about 15 times less than deep ground water (Jones-1997). Of all the Earth’s water, fresh water is very limited (3%) compare to saline water (97%). Of all the limited and valuable fresh water, a huge amount of water (68, 7%) is permanently stored in icecap and glaciers and other huge amount of fresh water is stored as ground water. Approximately out of 37 million cubic kilometers of total fresh water about 8 million cubic kilometers of fresh water is stored as ground water. So ground water is a key source of fresh water.
Fresh water demand rise day by day, especially for irrigation purpose. The percentage of total irrigation water increased 23% in 1950 to 42% in 2000. Water shortage increased dramatically and it is projected that around 3 billion people will be water stressed by 2025. Increasing demand of water and decreasing availability of water create a significant pressure on groundwater and this ultimately depleted the ground water quality. At present, approximately 61% of total irrigation water has come from ground water. Expansion of agricultural field and decreasing pattern of usage of surface water, accelerates the over exploitation of ground water. Though over utilization of ground wateris the key factor for ground water depletion but there are also other important factors those have negative impact on ground water sustainability. Contamination or presumption contamination also has adverse impact on ground water. Agricultural chemicals like N, P, K, pesticides etc. percolate through soil and contaminate the ground water. Naturally occurring constituents like arsenic fluoride, chloride etc. contaminate the ground water and made the water unsafe.
The most important impact of groundwater depletion is loss of base flow. If the base flow is reduced then there are different crucial additional impacts take place. These are: increased magnitude and frequency of floods; loss of wetland and riparian vegetation; changes in channel morphology; accelerates erosion; increased frequency of drought and loss of biodiversity. Other impacts of ground water depletion are severe crisis of safe drinking water and irrigated water. Ground water, as a valuable resource, we should meet its sustainability for our basic needs. Firstly, we should not exploit in an unsustainable manner. Ground water use policy should be sustainable and depends on basin’s recharge capacity. We should follow the ground water basin mass balance equation , where P= precipitation, E + Evaporation, T= Evapotranspiration, Q= Surface runoff ,G= ground water runoff, D= Deep percolation. In rural areas where ground water is the main source for drinking, implementation of well-head protection is necessity and secondly must control the waste water to percolating through soil and disposing of waste water to neighboring septic system. Tapping primary deep percolation and secondary shallow percolation are important measures for maintaining ground water sustainability. Baseline and time dependent hydrological studies are necessary to monitor the ground water. Conjunctive use of surface water and ground water, desalination, recycling and waste water reuse, water harvesting , increase recharge to the ground water system are also an effective measure to promote sustainable ground water supply. Protection of the water resource from depletion is not possible unless the users agree to cooperate and manage the resource themselves in a sustainable manner. More over state also needs to play a key role of facilitating and fostering community action for sustainable management. Lastly awareness should be raised towards ground water sustainability.