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Recharging aquifers — a solution to water scarcity

India is the highest user of groundwater, but with only 8% of rainwater being captured.

We begin with some hard-hitting facts: though India is the highest user of groundwater in the world with consumption of over 70 per cent of what is available, only eight per cent of rainwater is captured.

A common reason for water over-exploitation is the geometric increase in population. People are migrating to cities and hence, the population is not uniformly distributed. Economic and social changes triggered by rapid urbanisation have altered water requirements and consumption patterns in areas with hard and impervious surfaces. This is the urban scenario.

Absence of ponds

In villages, till a few years back, ponds were vital water resources that were very efficient, as the same water was used time and again. Unfortunately, these have now dried up or have been converted into wastewater collection pits, rendering them not only useless but also as a breeding ground for diseases. In the absence of these resources, water supply crunches are inevitable. Since the groundwater in villages have also become contaminated over time, villagers are left dependent on water sources away from the village.

Consider the agriculture scenario in India: water-intensive crops have always been preferred by farmers, as they are more remunerative. This is despite dependency on water resources or rain, low productivity of the land, and other vulnerabilities. Societal and economic pressures cause the continuation of this trend. Another irony: India is an exporter of water-intensive crops/produce, while it imports pulses (among others). This means we are basically "exporting" water on one hand, while struggling with water scarcity on the other. Another factor that adds to these woes is India’s political system, which responds to the needs of the farmers through generic, "mass-tailored" solutions (monetary support schemes to farmers) without considering the implications.

For example, in a few States electricity supply is free or highly subsidised for agriculture. Some of the implications of this are the continued cultivation of water-intensive crops, and the extensive irrigation of land, depleting land and/or crop productivity. Broad solutions include careful observation of water-usage patterns, understanding how the water consumed is "fed back" whenever and wherever possible, use of better and efficient irrigation systems, and technologies such as hydroponics or aeroponics.

Coming to the industrial sector, the usage of water is not very high comparatively. Additionally, this sector boasts of being organised and productive, which means that it has the potential to produce, recycle, and reuse water without loading the environment. Some industries in water-scarce areas have not only created their own sources of water supply, but have also shared this resource with neighbouring communities. In drastic comparison are some industries located in water-sufficient areas that mine the groundwater, contaminating not only the water, but also the soil and the air. This is indeed food for thought, as there is a solution within the problem itself just waiting to be applied.

Rainwater harvesting

In India, over 90 per cent of the rural water supply, over 50 per cent of the urban water supply, and over 70 per cent of the agricultural water supply are sourced from aquifers, In layman’s terms, aquifers are porous and permeable layers of the earth that are capable of storing and transporting water. As we keep exploiting water resources, the need for a proportional recharge of the aquifer stands. If this does not happen, the dry zone created above the water table deepens.

Let us understand how water percolates down and recharges the aquifer. The earth’s crust comprises of layers of soil. When it rains, the top layers are saturated with water, expelling air from the voids between the particles. If the supply of water sustains, it will be transmitted to the underlying layers, saturating them too. However, if it is short-duration, the sun will dry the upper layers and the water from the lower layers will travel back to the upper layers via capillary action; and the aquifer remains depleted.

Because of climate change, rainfall (especially in semiarid regions) is becoming intense and short-spanned with a huge run-off, affecting the recharging of aquifers (no recharge is possible due to low retention of rainwater on the soil, and the resulting low rate of percolation). This indicates that we need to replace the "layer-by-layer saturation" for recharging the aquifer with a more sustained method: recharge through rainwater harvesting. This can be done easily by constructing recharge shafts/wells within geographic proximities in order to benefit the water levels locally, through harvesting, collecting, and recharging. We must minimise water drainage and direct water to the aquifer as soon as possible (especially in areas where there is less or no contamination of water). In urban areas, where land is scarce and precious, parks can be constructed a level below the ground or road level to allow the direct drainage of rainwater into a constructed aquifer recharge system.

There are solutions available to tackle over-consumption of water. What is most important is the cost-effective, timely, and sustained implementation of such solutions to recharge aquifers directly. Therein lies the key!

(Lalit Mohan Sharma is Director, Adaptive Technologies, Sehgal Foundation.)

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Printable version | Feb 23, 2020 2:23:10 AM | https://www.thehindu.com/opinion/op-ed/recharging-aquifers-a-solution-to-water-scarcity/article24269547.ece

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