By Biplob Chatterjee
Water is a natural resource that is highly vulnerable to climate change and uncertain weather patterns. Complex water-related disasters, such as drought, groundwater depletion, pollution, and non-availability of safe drinking water, are growing in numbers and urgency. A 2018 report by NITI Aayog cautioned that India is facing its worst ever water crisis, with the demand for potable water projected to outstrip supply by 2030. Given this urgency, the government and stakeholders need to work at building water resilience and prepare India’s citizens for supply threats in the long term. However, devising a coherent strategy and policy framework for India’s complex federal structure is a daunting challenge, mostly due to differing cultural perceptions around water. For example, each watershed is different and must be treated based on the scientific characterisation of the watershed. Geovale Services recently carried out detailed hydrological – hydrogeological investigations in the Chikkaballapur district in Northern Karnataka, which illustrated the water management challenges in the region for stakeholders.
Chikkaballapur is a rich horticulture region of India with approximately 500 km2 area for growing fruits, vegetables, spices, flowers, and aromatic plants; this crop is worth more than rupees 800 crores annually. Thus, an enterprising horticulturalist can earn upto ten to fifteen lakhs rupees annually, for every acre of cropping.
However, the happiness of a rich farming community is under threat. Farmers are finding groundwater — their only water source – to be depleting rapidly. In response, they are desperately drilling deeper and deeper, and at newer locations, but failing. Water levels in groundwater aquifers — which used to be at 20 m below the surface circa 2000 — have now fallen to more than 300 to 350 m from the surface in discrete narrow zones and running dry thereafter. This is devastating, as earlier, every farmer was told that the use of highly acclaimed drip irrigation technology would be a panacea. Instead, they now find their water sources nearing exhaustion.
Chikkaballapur, by virtue of being close to Bangalore, is also attracting large real estate developers, farm houses, resorts and others interested in wealth creation. All are scrambling to stake out the last drops of available groundwater.
The annual groundwater consumption of a grape farm (as an illustration here) is about 3000 m3 per acre for a double crop of approximately 20 tonnes of grapes (Bangalore blue, Arnab e Shahi and Seedless varieties are grown here with variable yields). The water footprints for other horticulture produce are similar. A simple calculation provides the water balance of the area. Chikkaballapur recieves an annual rainfall of about 750 mm, 85% of which precipitates in 60 rainy days during a normal monsoon. However, nature allows a recharge of only about 3% — or less than 100 m3 — of water into the hard rock aquifers of the region annually. All the remaining water either evaporates or drains down as surface run-off. Horticulturalists who use drip irrigation technology are thus overdrawing ten to twenty times the natural groundwater recharge rate. The overpumping of water, especially in last couple of decades, has resulted in a near complete exhaustion of aquifers — storage reservoirs for a large amount of water underground. It’s also notable that since 2012, Chikkaballapur has actually been receiving 20 – 30% rainfall than normal, with the exception of a normal year in 2017.
Globally, acquifers can hold an estimated 1000 times more water than surface storage. The water holding capacity and permeability can, however, vary significantly depending upon the pore space in the rocks making the aquifer. Chikkaballapur’s hard granite rocks have a loose weathered regolith capping above a zone of horizontally and vertically fractured rocks going down to about 100 m below the surface, thus defining the top aquifer. The top aquifer also holds the dynamic groundwater resource, where a 3% annual recharge contributes to water replenishment. Below this zone, the lower aquifer is defined by multiple narrow or isolated zones of widely spaced and steeply dipping fractures down to depths of about 350 m. These have extremely slow water recharge from the top aquifer, which make them static resources.
The active conservation of aquifers should ideally be a significant part of our climate resilience measure for potential draught years, or for a time like a Cape Town Ground Zero condition. In Chikkaballapur, the top aquifer with dynamic resource has mostly dried up due to overpumping. Farmers are now mining out the static water resource from the bottom aquifer, which has negligible recharge potential. The indiscriminate tapping of these groundwater storages at a rate that is higher than it can be replenished, without a real emergency, is a gross irresponsibility on part of all the stakeholders – from the farmers to irrigation technology suppliers, to the ground water survey departments who failed to warn statutory agencies about the dangers of their actions.
In order to develop resilience, and prepare for any future water-related crises, a collaborative Water Stewardship is the need of the hour. Water conservation programs can consider an optimum sized sub-watershed as a unit, which must be hydrologically – hydrogeologically mapped out in detail. Watershed management programs should be based on detailed aquifer characterization for engineering interventions in order to create sustainable aquifers over the next five to ten years. Stakeholders must collaborate to ensure sustainable ground water abstraction for the next few years. Statutory interventions including monitoring of abstraction through use of modern IoT based technologies may be considered and if required, end user taxation for extraction above a pre-determined allocated water quantity should become the norm. All farmers must be educated about water supply constraints and the need for water demand optimisation.
India needs to be a good example in Water Stewardship, and allow other regions to emulate its success. Since Chikkaballapur shares so many similarities with Bangalore, a successful project here could lead to the rejuvenation of Bangalore’s aquifers as well. With many farming communities in India that dependent on ground water irrigation reporting continual falling water tables, Chikkaballapur has the potential to be a role model in water resilience .