JOIN USRestoring W Ghats critical in dealing with water crises
Bengaluru is now receiving 1,350 million litres per day (MLD) of drinking water against the requirement of 1,440 MLD. The supply is likely to reduce further as water remaining in the four Cauvery basin reservoirs, namely the Krishnaraja Sagar (KRS), Kabini, Harangi and Hemavathi is only about 15.8%, 6%, 16.4% and 6.4%, respectively, of the total live storage capacity and monsoon rains are still far away.
Fresh water is a produce of nature. Received as rain and snow, water becomes available for human use from rivers, lakes and underground aquifers. Three environmental factors cause rainfall in the peninsular Indian region. First, land-ocean temperature differential that drives windflow from ocean to land; Secondly, presence of the Western Ghats to obstruct the rain clouds; and thirdly, forests and inland water bodies, as they contribute large quantities of moisture through evapotranspiration to the atmosphere.
According to the Indian Meteorological Department, rainfall in the Western Ghats region has registered a declining trend since 1950. This has implications for the availability of fresh water in the river systems of peninsular India. During 2016 monsoon, the upper catchment area of river Cauvery in the Western Ghats in Kodagu district has received a 34% deficient rainfall.
The demand for fresh water is managed by harvesting surface as well as ground water. Currently, to manage the increasing demand, water-use efficiency measures such as promoting drip irrigation and wastewater recycling are adopted. In extreme cases, even rationing of water and transporting water by railways to water-shortage areas is resorted to. With rise in demand however, such management is likely to become more challenging.
With the demand heading northwards, can we continue to ignore the supply side of water? The answer to this is a clear ‘no’. We understand that the availability (supply) of water in the peninsular Indian region is determined by two factors: one, quantity of rainfall; and two, hydrology-based natural distribution of rainwater. This prompts us to ask some questions. One, can rainfall be enhanced? And two, can hydrology be influenced? The scientific understanding about the role of forests in the terrestrial hydrological cycle suggests that answer to both these questions is in the affirmative.
Forests influence rainfall and hydrological cycle through multiple mechanisms. First, large-scale full-canopy forests such as the Western Ghats forests release enormous quantities of moisture through evapotranspiration and create a low pressure column over forest areas due to rising and condensing moisture leading to suction of moisture-laden winds from ocean.
As a result, additional quantity of atmospheric moisture (rainfall) is appropriated from ocean in favour of land. Secondly, forests emit volatile organic compounds and discharge pollens, which serve as cloud seeds. Thirdly, particularly during the monsoon-receding phase, forests contribute critical moisture to the atmosphere that results in the extraction of additional rain from a sub-critical moist atmosphere. Thus, forests enhance continental rainfall by intensifying the hydrological cycle.
Restoring Western Ghats: The interior Indian peninsular zone is naturally semi-arid. Without the Western Ghats, it could easily be a desert, as the southwestern monsoon winds would crossover to Bay of Bengal without raining. The Western Ghats system not only causes orographic rainfall but also supports extensive forest cover over more than 58,000 km. The river systems and hydrology in peninsular India depend on the Ghats’ ecological wellbeing.
Western Ghats is a large social ecological system (SES), as more than five crore people inhabit and influence the Ghats. The direct socio-economic influence of Western Ghats spreads much beyond the Ghats and covers almost the whole of peninsular region. Recognising this, the Western Ghats states (Kerala, Tamil Nadu, Karnataka, Goa, Maharashtra and Gujarat) as well as the Government of India have taken several measures to preserve the integrity and ecology of the Ghats.
However, the current level of anthropogenic disturbance poses a great challenge to maintain the functionality and water value of the Ghats. Stress from a changing climate would further add to this challenge. Vulnerability assessment shows 30%, 36%, 19% and 15% area of the Western Ghats in Karnataka having low, medium, high and very high vulnerability, respectively.
Vulnerability of Ghats
Vulnerability of the Ghats is likely to exacerbate in a warmer world, which will have implications for yield and availability of water in peninsular India. Biophysical restoration of the Ghats is therefore necessary to reduce their vulnerability and strengthen resilience to climatic as well as non-climatic stresses.
The latest government initiative to adopt eco-sensitive area (ESA) classification expects to establish a development approach for the Ghats that limits disturbance, restores ecology and promotes sustainable development. The draft ESA notification intends to constitute 56,825 sq km area of the Western Ghats (35% of total area) as ESA. It mentions that there would be no displacement of people from the ESA, and agriculture and plantation activity could continue.
However, the following activities would be prohibited within the ESA: mining (existing mining activity to be phased out over next five years), thermal power plants, ‘Red category’ industries, and new buildings having 20,000 sq m or more construction area (no restriction on repairs and renovation of residential houses). ESA in Karnataka spreads over 20,668 sq km in 10 districts.
Restoration of forests and ecology of the Western Ghats is a risk-reduction approach against water shortage in the peninsular India. Restorative management of the Ghats is urgent, as the impact of climate change is aggravating and restoration measures would be useful only before the ecological thresholds are reached.
Deferment of restoration would reduce the manageability of restoration and render the restoration cost prohibitive. Cost effective win-win strategies for people inhabiting the Ghats would be fewer and difficult to evolve with passage of time.
(The writer is an IFS officer working in Water Resources Department, Karnataka)