Groundwater in India: Portfolio and Risk
MNNIT Allahabad, UP, India
Groundwater is the water that seeps through rocks and soil and is stored below the ground. The rocks in which Groundwater is stored are called aquifers. Aquifers are typically made up of gravel, sand, sandstone or limestone. Water moves through these rocks because they have large connected spaces that make them permeable. The area where water fills the aquifer is called the saturated zone. The depth from the surface at which Groundwater is found is called the water table. The water table can be as shallow as a foot below the ground or it can be a few hundred meters deep. Heavy rains can cause the water table to rise and conversely, continuous extraction of Groundwater can cause the level to fall.
Groundwater is extremely important for drinking water and food security, besides rendering a significant service toward human health and ecosystem [Gleeson et al. 2016]. At many places, aquifers are the only source of available water for drinking and irrigation, rendering groundwater as the most abstracted raw material on the Earth [NGWA 2016]. In the changing climate scenario, the role of groundwater is significant, due to its relative stability in terms of both quality and quantity. India, as a country, is tilted toward groundwater for its societal needs. With 243 km3 extraction annually, India is the largest consumer of groundwater in the world, consuming more than the cumulative draft of second and third highest consumers, i.e., Republic of China and USA, respectively [NGWA 2016]. Nearly 85% of rural drinking need, 62% of irrigation need, and more than 50% of urban water demand of the country are met up from aquifers.
India’s groundwater story is unique and interwoven in its journey toward achieving food security. The country has witnessed atomistic groundwater development, through private participation, where the millions of landowners drilled their own wells. At present, the number of wells used for irrigation in the country is pegged to be more than 25 million. Besides providing irrigation, the wells boast rural economy and employments.
Growing population, urbanization, industrialization, and overall development of infrastructural facilities with improved lifestyle have put water in a competitive sectoral demand more than other parts of the world. There is a radical reduction of per capita annual availability from 5177 to 1545 m3 since India’s independence. All global prediction say large part of India is going to be water scarce by the year 2030. Aquifers, being comparatively safer source of potable water and being distributed in all types of terrain and in agro-climatic zones, the pressure from increasing water demand will be mainly focus on groundwater development and management. Central Groundwater Board being the apex organization under government of India in the domain of groundwater exploration, monitoring, and management has a stupendous task in fostering sustainable development of this precious natural resource involving the stakeholders, planners, researchers, and implementing agencies in state level.
As of April 2015, the water resource potential or annual water availability of the country in terms of natural runoff [flow] in rivers is about 1,869 Billion Cubic Meter [BCM]/year [Water and Related Statistics, 2015] However, the usable water resources of the country have been estimated as 1,123 BCM/year. This is due to constraints of topography and uneven distribution of the resource in various river basins, which makes it difficult to extract the entire available 1,869 BCM/year. Out of the 1,123 BCM/year, the share of surface water and Groundwater is 690 BCM/year and 433 BCM/year respectively. Setting aside 35 BCM for natural discharge*, the net annual Groundwater availability for the entire country is 398 BCM [Central Groundwater Board website]. The overall contribution of rainfall to the country’s annual Groundwater resource is 68% and the share of other resources, such as canal seepage, return flow from irrigation, recharge from tanks, ponds and water conservation structures taken together is 32% [Groundwater Yearbook 2013-14]. Due to the increasing population in the country, the national per capita annual availability of water has reduced from 1,816 cubic meter in 2001 to 1,544 cubic meter in 2011 [Water and Related Statistics, 2015]. This is a reduction of 15%. Statistics regarding water resources in India are shown below in Table 1.
Table 1: Statistics regarding water resources in India
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Sources: Water and Related Statistics, April 2015, Central Water Commission; PRS.
Groundwater resources in the country are assessed at different scales within districts, such as blocks/ mandals / talukas /watersheds. Groundwater development is a ratio of the annual Groundwater extraction to the net annual Groundwater availability. It indicates the quantity of Groundwater available for use. The details of groundwater stressed areas in India is shown below in Figure 1.
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Figure 1. Groundwater stressed areas in India [Source: IWMI]
The level of Groundwater development is very high in the states of Delhi, Haryana, Punjab and Rajasthan, where Groundwater development is more than 100%. This implies that in these states, the annual Groundwater consumption is more than annual Groundwater recharge. In the states of Himachal Pradesh, Tamil Nadu and Uttar Pradesh and the Union Territory of Puducherry, the level of Groundwater development is 70% and above. In rest of the states, the level of Groundwater development is below 70%. Over the years, usage of Groundwater has increased in areas where the resource was readily available.
GROUNDWATER ABSTRACTION AND CONSUMPTION
Experts believe that India is fast moving towards a crisis of Groundwater overuse and contamination. [Kulkarni et al 2014] Groundwater overuse or overexploitation is defined as a situation in which, over a period of time, average extraction rate from aquifers is greater than the average recharge rate. In India, the availability of surface water is greater than Groundwater. However, owing to the decentralized availability of groundwater, it is easily accessible and forms the largest share of India’s agriculture and drinking water supply. 89% of Groundwater extracted is used in the irrigation sector, making it the highest category user in the country [Annual report 2013-14]. This is followed by Groundwater for domestic use which is 9% of the extracted groundwater. Industrial use of Groundwater is 2%. The 50% of urban water requirements and 85% of rural domestic water requirements are also fulfilled by Groundwater. [The World Bank, 2010]
Over the years, there has been a decrease in surface water use and a continuous increase in groundwater utilization for irrigation. The largest component of Groundwater use is the water extracted for irrigation. The main means of irrigation in the country are canals, tanks and wells, including tube-wells. Of all these sources, Groundwater constitutes the largest share. Wells, including dug wells, shallow tube-wells and deep tube wells provide about 61.6% of water for irrigation, followed by canals with 24.5%.
The stage of groundwater development is not uniform throughout the country due to obvious reasons that govern the aquifer potential, recharge capability, and extent of groundwater exploitation. Groundwater overexploitation is confined in 1071 units of the country and in another 914 significantly where level of exploitation has exceeded 70%. All these units are largely concentrated in the NW parts, as well as deep in Penninsular India. These areas are also characterized by deeper groundwater levels.