GroundWater

What is Ground Water:

Groundwater is stored beneath the surface of the earth. It seeps into the ground through the soil and permeable rocks. The layer of rocks that store the groundwater are known as aquifers. These aquifers are usually made up of sand, gravel or sedimentary rocks like limestone and sandstone and are capable of storing large quantities of water.

Apart from aquifers, other ecosystems that are dependent on groundwater include rivers, lakes, wetlands, springs, etc. These not only depend on the groundwater for water replenishment but also for nutrients, maintaining the water temperature, stability, and buoyancy.

Current Groundwater Scenario in India:

With approximately 230 cubic km per year, India is the largest user of groundwater in the world. The majority amount of groundwater used is in agriculture. This is almost 25% of the total global water extracted annually. Nearly 80% of the water needed for drinking purpose in India is dependent on the groundwater.

As a large part of India’s economy is dependent on groundwater, it’s being overexploited. Due to this more than 25% of the groundwater blocks are classified as semi-critical, critical or over-exploited.

Groundwater over-exploitation occurs when the average water extraction rate from the aquifers is more than that of the recharge rate. The national groundwater is assessed on the basis of the total usage of groundwater to the total groundwater available annually.

Below table estimates the per capita availability of water in proportion to population.

Benchmarks:
WATER STRESS: Between 1700 and 1000 Cu.m /Year/Person.

WATER SCARCITY : Below 1000 Cu.m/Year/Person

How is Ground Water Level Measured:

Central Ground Water Board (CGWB) examine the groundwater on a periodical basis. The measurement is done with the help of multiple sensors that measure the water level at different aquifers. The Ground Water level module provides data four times a year, i.e, according to four seasons,
January to March (Post Monsoon Rabi),
April to June (Pre Monsoon),
July to September (Monsoon) and
October to December (Post Monsoon Kharif).

The pie charts below show the number of wells in all the states of India and Maharashtra. (Post Monsoon 2016).

According to the central ground water board, the total numbers of groundwater monitoring wells as on March 2017 are 1850 in Maharashtra.

Consequences of Groundwater over-exploitation:

According to the World Bank, about 15% of the food production in India is dependent on groundwater. This has led to the extensive use of groundwater. The increase in population and thus competition within the farmers has resulted in deepening of the wells.

Groundwater is directly or indirectly linked to the ecological and hydrological systems. It balances the flow of the river, sustains springs, etc. Its exploitation not only affects everything in terms of water availability but also in terms of water quality.

A Solution to save Groundwater:

Groundwater is a critical resource that is declining at a high rate. This is because the natural replenishment rate of groundwater is slow as compared to its exploitation. Hence there is a need to supplement the natural supply of groundwater. This can be done through Artificial Recharge of groundwater.

The term Artificial Recharge may be defined as the transfer of surface water to the required aquifer by human interference. That is, the artificial recharge method helps in accelerating the natural process of recharging the aquifer with the help of stored water. Injection well is an example of AR ( A process in which water is allowed to flow or pumped into the ground through a vertical pipe).

In India, rainfall is limited to three months a year i.e only during the monsoon season, and so the natural groundwater recharge is restricted to the monsoon period only. The Artificial Recharge technique extends this period to about two or three months post monsoon. According to the CGWB report on Artificial Recharge, some of the main criteria that need to be taken into consideration are;

I) Availability and assessment of the source/surplus water –
The source water availability may include the precipitation in the area, nearby stream or spring, reservoirs located nearby the area, treated municipal water, etc.

II)The storage space of the aquifers, geological boundaries, porosity, etc.

According to the Interim Report 2016 of Central Groundwater board CGWB, a number of Artificial Recharge (AR) project has been Implemented in various cities across the country. For example, in Maharashtra, one AR project is implemented in Raj Bhavan area, in Nagpur.

The water conservation and AR structures built here are successful in enriching the soil moisture content and recharging the groundwater

The concept of artificial recharge has many more advantages apart from just recharging the groundwater. These include environmental friendly solutions like controlling soil erosion, providing abundant moisture to the soil even during the dry season, making the stored underground water free from man-made or natural calamity, maintaining the quality and purity of water and reducing evaporation.

Conclusion:

With the increase in population, the demand for water will increase and the water available to us will decrease. For this there is an urgent need for the government to take some actions like groundwater monitoring and data collection, integrating strategic solutions where there is an over-exploitation of groundwater, imposing some strict regulations, etc. In short groundwater governance that is highly efficient and robust in the need of the hour. Also, more methods and techniques like Artificial Recharge, Rainwater harvesting, etc. must be implemented to improve and preserve the groundwater.