The conventional freshwater sources available in India are being currently overexploited, leading to widespread environmental degradation and depletion of freshwater resources especially groundwater. To sustain the needs of an increasing population and ecology, our consumption of water far exceeds the rate at which we are recharging water sources. We are faced with water scarcity and will find it hard to meet the future regional demands. We have a situation of relative scarcity, if we take into account the affordability of real costs of water supplies for purposes of irrigation and domestic use.
Integrated water conservation and management
To overcome the problem of water scarcity, considering the serious limitations and the high cost involved in enhancing water supply, a viable option is to prioritise water conservation. India has had strong cultural traditions related to collecting, storing and preserving water for various uses. These are reflected in our social fabric and institutions of community life.
At present, the amount of rainfall received in the country is to the tune of around 4000 billion cubic meter (bcm) in a year. Of this, a major portion of rainfall flows off as runoff, whereas the total water requirement of the country in all sectors such as domestic, agriculture, commercial and industrial is approximately 1200 bcm. If rainfall is collected and managed properly with the help of rainwater harvesting and artificial recharge structures for augmentation of ground and surface water, this can reduce the dependence on groundwater to the tune of about 500 bcm out of the total annual water requirement of 1200 bcm for all sectors.
The need for water conservation, augmentation and preservation was never more pronounced than now. In view of this, the National Water Mission started promoting citizen and state specific actions plans for water conservation through rainwater harvesting structures and artificial groundwater recharge structures.
Further, the National Water Policy 2012 inter-alia, recommends conservation of existing water bodies, rivers, river corridors, etc. From various platforms, Hon’ble Prime Minister has also given a clarion call to citizens to join hands for water conservation and to create a Jan Andolan on the lines of Swachh Bharat Mission. Therefore, a national campaign for creating awareness among every individual on water conservation needs to be initiated and promoted at national level.
“A campaign ‘catch the rain’ has been initiated as part of the “Har Kaam Desh Ke Naam” initiative. It tries to nudge states and stakeholders to develop rainwater harvesting structures before the onset of the monsoon. The government is working on setting up of district level rain centers, where anyone can avail information on rainwater harvesting techniques and expertise,” says Shri G. Asok Kumar, Mission Director, National Water Mission.
Need for robust guidelines on water conservation
To promote rainwater harvesting and artificial recharge structures there is a need to develop robust guidelines on water conservation practices bringing in the overall Indian perspective for regulatory, institutional, financial, technical and other relevant aspects. This is necessary because rainwater harvesting and artificial recharge structures will not be same for different climatic conditions and geological formations. In alluvial formations, aquifer parameters (porosity, permeability) are primary in nature, while in hard rock areas, the aquifer parameters (porosity, permeability) are secondary in nature.
Besides this, the success of rainwater harvesting and artificial recharge structures also depends upon the amount of rainfall received by catchment area, soil strata, geological conditions and number of rainy days. The rainwater harvesting and artificial recharge structures aims at augmentation of groundwater reservoir by modifying the natural movement of surface water utilizing suitable civil construction techniques.
Artificial recharge has become extremely necessary to ensure sustainable groundwater supplies to satisfy the needs of a growing population. Harnessing runoff in catchments by construction of water conservation structures such as gabions, check dams, bhandaras, percolation trenches and sub-surface dykes is essential.
In urban and semi-urban areas, rooftop rainwater harvesting technique is suitable and through this rainwater is captured from the roof catchments and stored in reservoirs. Harvested rainwater can be stored in sub-surface groundwater reservoir by adopting artificial recharge techniques. The urban housing complexes or institutional buildings have large roof area and can be utilized for harvesting roof top rainwater and recharging.
Recharging storm water
It is also observed in the recent past, rapid growth in the urban areas has led to stone slabs or pavers for footpaths and asphalted roads, which has led to high runoff and decline in groundwater recharge. As the roads are built sloped towards the sides, rainwater falling on the road is guided to the side drains. To increase groundwater recharge by percolation and decrease the flooding of storm water drains, infiltration trenches could be built by the side of the drain all along the road, wherever possible.
As the rainwater from the road flows into the infiltration trench, water percolates into the ground. These infiltration trenches may be exposed as walkways or paved with interlocking pavers, specially designed with gaps in between for water to flow into the infiltration trenches. Several technologies have come up to tackle water scarcity and storm water flooding issues in urban areas such as swales, bio-filtration system and infiltration trenches.
For example, Bioswales (Rigofill) system features universal components for infiltration, retention and storage of storm water runoff. It is easy to install, camera-accessible and saves space. It provides a storage volume of 406 liters per day with a gross volume of 422 liters per day. With over 96 percent storage volume, it stores three times more water than gravel swales. This makes them an ideal alternative to gravel swales, which require more space and extensive excavation. This is an innovative technology, which can be used to tackle urban storm water flooding issues and reuse filtered and treated flooded water for artificial groundwater recharge and water storage in huge underground storage tanks for future use.
Mainstreaming rainwater harvesting through regulatory levers in urban areas is a very important aspect. Government schemes such as Atal Mission for Rejuvenation and Urban Transformation (AMRUT), is prioritizing urban reforms, including promotion of rainwater harvesting. This has led many states to incorporate provision of rainwater harvesting in their respective building byelaws.
Delhi Jal Board also started various water conservation initiatives such as promoting rainwater harvesting by giving financial assistance up to Rs. 87 lakhs to 176 institutions for rainwater harvesting system installation and also provisioned for rebate on water bills. Around 439 rainwater harvesting systems have been installed by Delhi Jal Board across Delhi, which has created rainwater harvesting potential of about 18,000 to 366,000 litres depending upon the roof top area.
As a part of Mahatma Gandhi National Rural Employment Guarantee Act (MGNREGA), water conservation and groundwater recharge practices are being undertaken at the rural level to tackle the problem of water scarcity. Gram sabhas are being involved in planning and prioritizing of works focused on improving livelihoods, infrastructure creation and natural resources management. MGNREGA is mainstreaming usage of geospatial tools for field investigation to identify appropriate location of rainwater harvesting and groundwater recharge structures development with their mapping on cloud, and in this regard, has partnered with National Remote Sensing Centre (NRSC).
Strategies that could be adopted for sustainable rainwater harvesting and recharging of groundwater includes outcome-based approach rather than output based, regular monitoring and handholding for water conservation, recognising good water conservation practices and disseminating new conservation practices. There is also a need to explore recycling of wastewater as an alternative source for rejuvenating urban water bodies, as seen in Hauz Khas lake, Delhi.
Qazi Syed Wamiq Ali is a Consultant (Water Resources Engineering), National Water Mission, Department of Water Resources, River Development & Ganga Rejuvenation, Ministry of Jal Shakti, Government of India.