One of the vilest things of human nature is that we often tend to take for granted that which comes easy to us. Rain is one such resource that we all rejoice in but never make an extra effort to capture for the future. Most of it drains into the oceans leaving behind a huge swathe of the population starving for water. With the recent forecasting of NITI Aayog regarding most of the Indian cities being on the brink of hitting Day-zero very shortly, the rainwater harvesting mechanism has gained traction in recent years. Though rainwater harvesting isn’t a modern mechanism, its need has been felt in the present day more than at any other point of time in human history. Before dwelling on the reasons behind this, let us first understand what Rainwater harvesting means.
What is Rainwater harvesting?
It is a technique or strategy for the collection and storage of rainwater, intended to be used for future practical purposes. The rainwater could be collected from any source, such as, from rooftops of buildings, ground surfaces, hill slopes, etc. In most cases, the rainwater is collected from rooftops and hard ground surfaces. Then this collected water is stored in a dedicated storage system which are exclusively built for the same purpose. The stored water could either be used for direct consumption or could be used to replenish the underground aquifers, depending on the purpose for which they have been built. Rainwater harvesting is regarded as one of the most socially accepted and environment-friendly strategies to preserve the water resources on the earth.
Types of Rainwater harvesting systems:
- Storage of rainwater in collection tanks: It is generally preferred in areas with moderate rainfall, as size of storage tank has its own limits. There are two sub-types under this category, which are as follows.
- Roof-top run off: In this, adequate piping channels are setup to collect the roof-top run off and are channelised into the storage tank setup below. These are increasingly becoming common in residential buildings.
- Surface run off: When the underlying stratum of the surface is impermeable, the surface run off rainwater is channelised into a storage tank that is built appropriately. These are built at both buildings and public places.
- Recharging ground water aquifers from rainwater: This is usually practised in areas which receive abundant rainfall, to the extent that exceeds the limits of storage tanks. This is again of two types.
- Roof-top run off: Rainwater that is collected on the roof top of the buildings is channelised by drainpipes into a filtration tank from which it flows into the recharge wells or soak pits.
- Run off from ground areas: The rainwater that is collected from the open areas is channelised by drainpipes to a recharge dug well, and from there water reaches the underground water table.
Historically speaking, the Water harvesting technique has been an age-old practice. The practice of storing and collecting rainwater for later use can be traced back to ancient times, the Neolithic Age, more specifically. Almost all the ancient civilizations of the globe have evidently been practising one or other form of such techniques. The first such archaeological evidence was traced from West Asia, where cisterns attached to the floors of houses to collect rainwater were found in Jerusalem and Israel.
Coming to the sub-continent, the history of rainwater harvesting can be traced as far back as the Harappan water-harvesting system. Rainwater harvesting structures were found beneath the ground along the Manhar river in Khadirbet of the Kutch district of the Harappan civilization. Another such example can be traced from around 300 BC when farming communities from present-day Pakistan, Afghanistan, and northwest India were found to be practising harvesting of rainwater. Ancient rainwater collection networks can be found at Karle Buddhist caves, the Shivganga tank in Thanjavur, the Veeranam tank in Cuddalore, etc.
India bags the notoriety as the highest extractor of ground water in the world as it annually draws 251 billion cubic meters of groundwater. India banks on ground water to meet more than 80% of its water demand. Estimates say that 85% of the rural and 50% of the urban population in India are dependent on groundwater for fulfilling their needs. As a result,
- As per the 5th Minor Irrigation Census, the groundwater level in India has declined by 61% between 2007 and 2017.
- It also reported that more than 1,000 blocks in India have become water stressed.
- According to the NITI Aayog’s composite water index, 54% of India’s groundwater wells are depleting.
- It further observed that about 40% of India’s population possibly would lose the access to drinking water by 2030.
- Many of the Indian metro cities are on the brink of reaching Day zero in the immediate future.
Above statistics spell a doom and are indicative of the imminent crisis that India is slipping into. To arrest the further worsening of the crisis, its high time India should formulate strategies to restore its fast-depleting water tables. Rainwater harvesting is one of the most inexpensive, efficient, and sustainable techniques to achieve the goal of replenishing underground aquifers.
How much Rainwater can be harvested?
Below, we shall see illustrative theoretical calculation that underlines the massive potential for rainwater harvesting in any place. This procedure can be replicated to calculate the potential for any plot of land or roof top area, factoring-in the rainfall data for a particular area. For example, let’s see Chennai’s case. Consider a plot of size 100 sq. metres. The average annual rainfall in Chennai is approximately 44 inches or 1100 mm.
Area of plot = 100 sq. metres
Height of rainfall = 1.1 m (1100 mm or 44 inches)
Total volume of rainfall over the area of plot = Area of plot X Height of rainfall =
100 sq. metres x 1.1 m = 110 cubic metres (1,10,000 litres)
Even if we assume that only 60% of the rainwater could be harvested, that amounts to 66,000 litres of water being collected over that plot. This volume is about four times the annual drinking water requirement of a 5-member family. Now, we can comprehend the potential of rainwater harvesting if it could be effectively implemented across the nation.
- Reduces flooding and erosion: It reduces the surface runoff of rainwater and thereby reduces the volume of peak water flow into the river channels, creeks, streams, etc. This reduces the intensity of floods, thereby saving valuables lives and property. Similarly, the reduced water flow on the surface and in water channels reduces soil erosion, which, if left unchecked, would be detrimental to the ecosystem.
- Reduces water bill: Storage of rainwater in the domestic collection tanks would obviate or lessen the need to draw underground water or to buy water. This would save costs incurred on water extraction. Also, in agriculture, the water drawn from storage tanks would lessen the water costs.
- Easy to install: The infrastructure required to setup harvesting system is quite simple, easy to operate, and maintain. All it needs is a network of pipes, filter, and a storage tank.
- Replenishes ground water: Harvesting rainwater for daily needs would lessen the pressure on groundwater. As India is already slipping into the water crisis with water tables decking in more than 50% of its areas, reducing the dependency on its ground water by harvesting rainwater is an imperative. Rainwater harvesting not only disburdens ground water but also helps rejuvenate the water tables through recharging the aquifers.
- Reduces water wastage: It saves millions of gallons of water from going down the drains. Most of the rainwater in India often ends up in seas, especially during the monsoons. Harvesting techniques could prevent this wastage of water resources.
- Can be used for gardening and agriculture: Instead of sucking underground, the harvested water can be effectively used for home gardening and agricultural purposes. As we all know that agriculture is the prime culprit behind depleting water tables, this could alleviate the looming crisis partially.
- Can be used for non-drinking purposes: It can cater to the needs like washing purposes, cleaning, bathing, etc.
- Unreliable rainfall: India’s rainfall is highly dependent on monsoons, which are notorious for being erratic and unpredictable. Moreover, Indian monsoons have unequal distribution in terms of both spatial and temporally. As a result, it isn’t a reliable source of water.
- Installation costs: It incurs some initial costs to build the piping and storage network.
- Storage limits: The size storage tanks are constrained by the available space and hence they can only store limited amounts of water.
- Unsuitability: The second category of water harvest system that we have discussed earlier, aren’t conducive in areas with irregular surfaces. There should be constant slope or plain surface to setup such harvesting networks.
- Lack of awareness: Still, majority of Indian’s aren’t aware of the advantages and know-how of rainwater harvesting mechanism. Lack of concern for depleting water resources is another factor.
- Periodic maintenance: Its infrastructure demands periodic interventions in terms of maintenances, which incurs fair amount of costs, which dissuades people.
- Treatment of rainwater: The runoff rainwater couldn’t be utilised for human consumption like drinking, bathing, etc., as they are riddled with dirt and several undesirable components. Hence, it must be treated using any one of the techniques, like subjecting it to chlorination, boiling, direct sunlight, etc.
Despite living in the 21st Century, it is bemusing to note that in a country of more than 1.3 billion people and 4100 towns and cities, only two cities- Thiruvananthapuram and Kota, could avail continuous, 24×7 water supply, and all those mega-cities with a population greater than 1 million, get water for only around 3-4 hours a day. This worrisome picture could be attributed to many factors ranging from natural phenomena to anthropological negligence. As the alarm bells are ringing louder, governments at both levels have formulated several initiatives to address the crisis.
Union government’s efforts
- Catch the Rain campaign: It is a joint effort of National Water Mission(NWM) of Ministry of Jal Shakti and Nehru Yuva Kendra Sangathan (NYKS) of Ministry of Youth Affairs and Sports. Its key aims are,
- Encourage all the stakeholders to develop Rainwater Harvesting Structures (RWHS) that are appropriate for the climatic conditions and sub-soil strata to collect and store rainwater.
- Effective campaigning through awareness generation, using information technology, communication, etc.
It involves scores of activities like construction of harvesting pits, rooftop RWHS and check dams, removal of encroachments and desilting of tanks to increase their storage capacity; removal of obstructions to decongest the channels which bring water from the catchment areas; repairs to traditional storage structures to recharge the aquifers; opening Rain Centres in each district, which will act as a technical guidance centre to the district.
- Mahatma Gandhi National Rural Employment Guarantee Act: Its activities include improving groundwater harvesting and building water conservation and storage mechanisms.
- The Rainwater (Harvesting and Storage) Bill, 2016: In 2016, the Rainwater (Harvesting and Storage Bill) was introduced in Lok Sabha, as a private member’s bill, by the then Member of Parliament- Dr. Kirit Prembhai Solanki, to provide for compulsory rainwater harvesting in every government, residential, commercial, and institutional buildings. Some of its provisions includes,
- construction of rainwater harvesting structures on properties having an area greater than or equal to 1100 square meters to meet a part of its total requirement of water.
- The government to formulate an action plan & strategies to educate the public about rainwater harvesting through various forums like the internet and other relevant campaigns; encouraging and providing financial assistance to Non-Governmental Organisations and other agencies actively engaged in rainwater harvesting.
- It also proposed a penalty of imprisonment up to two years and/or a fine up to Rs. 10 Lakh for violation.
However, even after the lapse of five years and one general election since its introduction, the Bill still languishes in parliament awaiting to see the light of the day.
- The government is planning to construct about 23 lakh artificial recharge and rainwater harvesting structure in rural areas and 88 lakhs in urban areas.
- Model Building Bye Laws, 2016: The Ministry of Housing & Urban Affairs has notified the Model Building Bye Laws, 2016 for guidance of the States/UTs on ‘Rainwater Harvesting’.
- Aims to regulate the over-exploitation and consequent depletion of ground water through some of the techniques that include rainwater harvesting.
- It would enable States/UTs to enact suitable ground water legislation, which also includes provision for rainwater harvesting.
- 33 States/UTs have adopted the rainwater harvesting provisions.
- As per Model Building Bye Laws- 2016, provision of rainwater harvesting is applicable to all residential plots above 100 sq. metres
State governments initiatives
Different state governments have formulated different strategies, basing up on their geographical and socio-economic factors.
Himachal Pradesh: All buildings, both existing and new, residential and commercial complexes, spanning over 1000 square meters should mandatorily have rainwater harvesting systems and storage units, proportional to the area of the terrace. All toilet flushes are to be connected to this storage unit.
Tamil Nadu: According to the Tamil Nadu Municipal Laws (ordinance) of 2003, the state government made it compulsory for all public and private buildings in the state to build and install rainwater harvesting systems, or the municipal authorities would build them and recover the costs from the property holder as property tax.
Similarly, many other states like Maharashtra, Madhya Pradesh, Haryana, Karnataka, etc have their own statutes to implement rainwater harvesting schemes in their respective states.
Success stories: Rainwater harvesting is considered the answer to India’s water woes. The practice has been fruitful in most parts of the country. However, some states have experimented with telling effect.
Tamil Nadu: The Rainwater Harvesting (RWH) scheme of the state was a brainchild of the then Tamil Nadu chief minister J Jayalalitha and was launched in 2001 with an aim to replenish water sources and improve ground water levels in the crisis-ridden state. During the launch, the scheme met immense resistance from the people as it mandated all the residential buildings to have rainwater harvesting structures. But two decades down the line, the tables have turned as the scheme had succeeded in increasing the water tables of the Chennai metro significantly.
Rajasthan: With a population of 70 households, Bajeena is a hill village situated 14 km away from Ranikhet in Rajasthan. A traditional water spring, locally called ‘Naula”, is located in the peripherals of the village. Due to the drying up of the water spring for myriad reasons, villagers in Bajeena have been facing an acute shortage of water, especially during the dry season. To find a solution, the women folk of the village have embarked on a mission to construct minor reservoirs on the hill slope to collect and store rainwater flowing down the hill slope. These reservoirs in turn recharged the traditional “Naula”. The next monsoon, this indigenous mechanism worked wonders for the village, and they overcame the water shortages, thanks to the replenished Naulas. (This study conducted by TERI)
The following measures would go a long way in effectively implementing the rainwater harvesting in India and there by evade the impending crisis.
- Collaboration of efforts: There should be a synergy between efforts of individual ministries, i.e., ministry of drinking water, ministry of rivers, ministry of rural development, etc. The fragmented efforts of various agencies should be consolidated so that resources could be utilised efficiently.
- Decentralisation: The ground level initiatives like rainwater harvesting, demands active participation of the stake holders and devolution of powers to the grass-root levels. Panchayats should be assigned a greater say and role in formulating plans and in constructing rainwater harvesting structures.
- Honest efforts from states: Since, water is a ‘State’ subject, centre could do little in terms of the implementation of RWH (Rainwater harvesting) schemes and programs. It need sincere and dedicated efforts from the states for the actual ground implementation of the schemes formulated by the centre.
- Civil societies: Governments should take the civil society organisations onboard to disseminate technical knowledge and awareness to the people and thereby help them install RWH structures in their households and villages.
- Subsidies: Government should mull over providing subsidies to the RWH equipment to encourage public to compliment the efforts the government.
- Effective laws: Strict laws should be legislated at all three levels of the governance. Offenders should be penalised or brought to the book, which unfortunately isn’t the case so far. The laws so far have met only lax implementation. Most of the public are not even oblivious of the laws regarding RWH in their respective state governments. Onus lies up on the government to generate awareness among the public regarding the RWH.
- Incentivising the states: Union government should ponder over adding RWH performance of the states as an additional criterion for performance-based grants, released by the Finance commission.
With the clock ticking at alarming & unprecedented pace and most of the Indian cities increasingly getting closer to Day-Zero, it is imperative to look for the sustainable methods of water replenishment. Rainwater harvesting proves to be an excellent strategy in this regard. Since it is simple, affordable, and sustainable, governments and the citizenry should embrace the ancient wisdom & techniques and combine them with modern scientific advancements to make the best use of rainwater. With the per capita water availability falling below 1,700 cubic metres, India cannot afford any more laxity.
- (PDF) Success Stories in Water Harvesting from Bajeena and Naila Villages, Almora District, Uttaranchal (researchgate.net)
- The Plight Of Depleting Groundwater In Urban Areas | Go Smart Bricks
- Rainwater harvesting in India – iPleaders
- India Soon to Face Day Zero; Bengaluru, Hyderabad And 20 Major Cities to Run Out of Groundwater by 2020: NITI Aayog | India.com