---

ABSTRACT

As we all know water is essential, but too many of us think it is unlimited .In reality, fresh water is a finite resource that is rapidly becoming scanty. The best way to conserve water is its judicious use. Water conservation is a key strategy that aims to improve the water crisis in India. With changing rainfall patterns, the Indian government has started looking at means to restore the traditional systems of water harvesting in the country. Community based rain water harvesting is gaining popularity in different agro-climatic zones of India backed up by public or private support. Rain water harvesting not only provides the most sustainable and efficient way of water management but also opens the prospect of several other economic activities leading to empowerment of people.

With rapid climatic changes, increase in global temperature and population expansion, there is a scarcity of potable water in many countries across the world. The receding groundwater table is a serious concern around the world. Nearly 65 percent of the India’s reservoirs were running dry in June 2019. Six of the 17 water reservoirs of Maharashtra had dried out in summer 2019. The city of Chennai took the worst hit regarding potable water shortage over the years. Apart from causing an acute water shortage for industrial, agricultural and drinking uses, this water crisis also leads to imbalance in soil salinity. This acute water shortage is the result of excessive unchecked water use in for the above mentioned processes in the past few decades, fuelled by rapid industrialization, urbanization, and deforestation. A sustainable water management is urgently needed in today’s scenario, which requires understanding the value of rain, and to make optimum use of rainwater at the place where it falls. In this scenario, Rain Water Harvesting (RWH) can contribute considerably to tackle water crisis. The best option is to harvest the rainwater where we get it and store it appropriately (on surface or into the aquifer) for eventual recovery and use at times of need.

Rainwater harvesting:

Rain water harvesting defined as collection and storage of excess amount of rain water received during rainy season. For meeting the drinking water needs of rural areas particularly during the periods of drought presently rain water harvesting is used. It depends on the amount and distribution of rainfall, soil type, soil depth, topography and slope of the catchment area etc. The rainwater if not harvested and stored, mostly runs off the land surface and gets wasted. Places where the rains are intense and continuous over some days, the runoff turns into flood inundating vast tracts of land and damages life and property. Under scanty rainfall condition, part of it gets lost by interception by tree canopy, evaporation and run off leaving very little of it for storage and future use. Although water is renewable, it is a limited commodity. Therefore rainwater harvesting and storage become crucial in either case, for productive use by people, livestock and nature.

 

The Rising Global Concern on Rain Water Harvesting:

Fast population growth along with industrialisation, urbanisation, and agricultural intensification and water intensive lifestyles is resulting in a global water crisis. Rainwater harvesting is considered among the most appropriate technologies for efficient use. Things have changed over the past few decades and since 1980’s there have been mushrooming growth of grass-root level initiatives supported by enlightened government and donor agencies promoting and implementing rainwater harvesting technologies. Several international conferences were conducted worldwide to spread awareness among people to save water resources and practice rain water harvesting. The very first conference took place in 1979 in Honolulu, Japan on the use of rainwater cisterns for domestic water supply was held in Honolulu, Hawaii in 1982 attracting mainly academic participants. Adding momentum to international conferences, many regional, national, and local meetings and initiatives took place reinforcing the suggestion that the technology is now being given more attention globally than at any time prior to 1980. These counted in the efforts by the New Delhi based Centre for Science and Environment to revive traditional rainwater harvesting practices in India (Agarwal & Narain 1997); the establishment of a rainwater harvesting forum in Sri Lanka; setting up of People for Promoting Rainwater Utilisation (PPRU) in April 1995 in Tokyo, Japan and new initiatives such as the encouragement on rainwater application in modern mega cities such as Tokyo. In parallel direction, the Millennium Development Goal (7) of ensuring environmental sustainability has set out the target of reducing the proportion of people without sustainable access to safe drinking water to half by 2015. Currently, the Sustainable Development Goal 6 ensures access to clean water and sanitation for all. While significant progress has been made in enhancing access to clean drinking water and sanitation, billions of people—mostly in rural areas—still lack these basic services. Shortfall in freshwater resources by 2030 coupled with an escalating world population has the world careening towards a global water crisis. Recognizing the mounting challenge of water scarcity the UN General Assembly launched the Water Action Decade on 22 March 2018, to mobilize action that will help transform how we manage water.

 Techniques of Rain Water Harvesting

A. Run-off water harvesting

(i) Short term storage

(ii) Long term storage

B. Flood water harvesting

C. Rooftop water harvesting

 A. Run-off water harvesting

(i) Short term Storage

This method comprises the bunds construction on the contour of the catchment zone. These bunds grip the flowing surface runoff in the area situated between two end-to-end bunds. This type of structures consists of an earthen impartment. Such kinds of structures are typically used for irrigation of grasses, fodder, shrubs, trees etc.

(ii) Long term storage

The long term runoff harvesting is done for building large water storage for irrigation, fish farming, electricity generation etc. It is done by constructing reservoirs and big ponds in the area. The major factors affecting the construction of farm pond are selection of site, soil depth and soil type.

 1. Dug out Pond

The dugout ponds are constructed by excavating the soil from the ground surface. These ponds may be recharged by ground water or surface runoff or by both. Construction of these ponds is limited to areas having land slope less than 4% and where water table lies within 1.5-2 meters depth from the ground surface. Dugout ponds involve higher construction cost, therefore these are normally recommended when embankment type ponds are not economically feasible.

 2. Surface Pond

Surface ponds are constructed by partly excavating with an embankment and fed by surface run-off. Depression areas are considered to be suitable site for surface pond and its construction cost is also less.

 3. Spring or creek fed ponds:

This pond is fed by a spring or ground water. It keeps the pond’s water level fairly consistent, regardless of rainfall, but the moving water created by the spring could cause dangerous conditions – even if the aeration system is shut down for the season.

 4. Off stream storage ponds:

Off-stream reservoirs are created by partially or completely enclosed waterproof banks. Usually concrete or clay is used to build the embankments around an off-stream reservoir. The size of an off-river reservoir depends on excavated area and height of embankment.

 Lining of farm pond

To prevent seepage and percolation losses farm pond should be lined with certain material likebricks, stones, paddy husk with cow dung, cement with soil mixture, fly ash mixture, benitonite, agrifilm etc. Seepage and percolation loss is high in light soils than heavy soils. Lining reduces water loss by percolation and seepage by 95%. It also prevents upward movement of salts and stretches the time period of water availability. Farm pond with an apt lining can be used in pisci-culture and irrigation economically.

B. Flood water harvesting

The purpose behind floodwater harvesting is to store flood water in artificial, closed ponds made of different materials. 

 C. Rooftop Rainwater Harvesting

Rooftop rain water collection is the first step in this method. Rain water from the rooftops to a designed sump is transported by a network of drain pipes. The sump houses a filter unit. Hence, when the rainwater moves into the sump it first gets filtered and then remains in the sump. Then with the help of a pump the water can be pumped to an overhead tank for future use.

 Advantages of Rain Water Harvesting:

Rainwater harvesting delivers the long-term answers to the problem of water scarcity. Rainwater harvesting offers an effective strategy in areas receiving sufficient rain but inadequate ground water supply and surface water resources are either lacking or are insufficient. Overall, rainwater harvesting is perceived as a socially adoptable and environmentally sustainable practice having many advantages viz. 

·       It provides self-sufficiency to water supply in both developed and developing countries by supplementing the main supply.

·       It reduces pumping cost and overdependence on groundwater.

·       Rainwater harvesting in urban water system offers significant benefit for water supply  by reducing the need for clean water in water distribution systems.

·       It Improves quality of surface water by reduction of storm water runoff polluting freshwater bodies.

·       Rainwater harvesting systems can be employed as simple and effective methods to reduce soil erosion, flood and water stagnation.

·       It is an excellent source of water for plants and landscape irrigation since it has no chemicals viz. fluoride and chloride.

·       In addition to the above the RWH structure helps in awareness creation on the overall concept of RWH.

 

Cases of Community Based Rain Water Harvesting:

 

A. Rain water harvesting in low rainfall area: a case of Umaid Heritage housing complex, Jodhpur, Rajasthan

The Birkha Bawari is planned as a monumental RWH structure, in Umaid Heritage Township of Jodhpur which is based on the idea of both ‘Kunds’ and ‘Baoli’ which were the age old practices of RWH in Rajasthan. Jodhpur located closer to the Thar Desert is having public piped water supply distribution in the city. The city stores raw water coming from Rajiv Gandhi Canal into two impounding reservoirs. The city has recorded high ground water level with mostly brackish water. But Umaid Housing Complex area is having a low ground water level. Hence, initiative was taken to harvest and store the rainwater than restore as alternate source of water supply. In order to collect run off by gravity flow the lowest part of the site has been planned and designed as RWH storage structure Despite the fact that the traditional baolis and kunds were used to extract ground water, Birkha Bawari is mainly used to store rainwater from the site catchment zone.

 

B. Rain water harvesting in high rainfall area: a case of Goa University Campus, Taleigaon, Goa

In order to check the shrinking ground water levels and restore the aquifers to cut down the dependency on municipal water supply in Goa university campus, a rain water harvesting project was initiated in 2007. The University campus meets its water needs from municipal water supply and bore wells. Problem arises during the month of summer when bore wells dry up due to over exploitation of water. Although Goa belongs to high rainfall zone but because of its geological placement most of the water is lost to the sea. So, to find solution, they started using the technique of roof top rain water harvesting. The RWH has been contributing considerably to recharge of the local aquifer resulting an improved yield and sustainable addition of groundwater. The reduced pressure on the public water supply system and improved recharge has a positive environmental impact. At small scale, the system contributes toward the resource conservation. This activity can also gain carbon credit in terms of energy conservation for in-situ water rise instead of sourcing water from distant site of water supply.

 

C. Rain water harvesting in rural areas: an initiative by DHAN Foundation

Unlike urban areas, rain water harvesting practises are basically undertaken in rural areas for the purposes of irrigation, dry land agriculture, horticulture, ground water recharge, domestic, livestock, inland fisheries, duck rearing and for multifarious other similar purposes. DHAN Foundation is a development organisation working mainly in rural areas with a focus on water resources development and their local management. The organisation comprises highly motivated, well qualified and experienced professionals, who live in and work from the grass root levels, with a deep concern for poverty alleviation through developmental activities, and build people to become self-reliant. The rain water harvesting structures in villages are mostly beneficial for the small and marginal farmers who don’t have access to large reservoirs. DHAN Foundation set forth to re-establish the traditional rain water harvesting tanks in the villages to their original design, standard and performance efficiency and had undertaken the programme by organising the concerned people, listing their active participation, building their capacity and making them contribute a part of the cost of restoration in Tamil Nadu and Andhra Pradesh. DHAN Foundation had undertaken the rehabilitation programme of minor irrigation tanks on a participatory mode in three stages. During first three years on pilot basis, DHAN workers focussed on restoring the already existing structures, next three years emphasised on regeneration of farmer’s management and third phase concentrating on popularizing tank fed agriculture among the farmers of that region. This great initiative by DHAN foundation not only helped in restoring traditional rain water harvesting systems in the village, but also triggered confidence among villagers to take initiative and go for community based management of these structures.

In the present day, several parts of the world, counting Hawaii and the entire continent of Australia, encourage rainwater as the principal way of supplying household water. Similarly, on many Caribbean islands where rainwater is the most feasible water supply choice, homes, public buildings and resorts all amass rainwater to meet their needs. In Hong Kong, rainwater collection is done from skyscrapers to supply water requirements. It is a very effective and traditional technique to collect rainwater to the surface. Tamil Nadu is the leading Indian state to make rainwater harvesting mandatory. Tamil Nadu state government had stated on 30^th of May 2014 to establish around 50,000 rainwater harvesting structures at various places in the Chennai.

 

Conclusion and recommendation

Since rainwater harvesting leads to water supply which ultimately is connected to food security, this will prominently contribute to revenue generation. It has wide application in urban and semi-urban areas also where the reliability and quality of piped water is increasingly being questioned. Rain water harvesting not only offers the most viable and efficient way of water management but also unlocks the prospect of several other economic accomplishments and activities leading to empowerment of people at grass root. For this Government should come out with appropriate incentive structure and logistics support to make it a real success. To promote these public-private partnership and convergence approaches can be useful (Mukherjee and Maity 2015; Mukherjee et al. 2012).

 References

 Agarwal, A. and Narain, S., (1997). Dying Wisdom: Rise and fall of Traditional Water Harvesting Systems, Centre for Science and Environment. New Delhi, India: Centre for Science and Environment.

Mukherjee, A., Bahal, R., Burman, R.R., Dubey, S.K., Jha, G.K., (2012) Conceptual convergence of pluralistic extension at Aligarh District of Uttar Pradesh. Journal of Community Mobilization and Sustainable Development, 7(1), pp. 85-94. 

Mukherjee, A., Maity, A., (2015). Public–private partnership for convergence of extension services in Indian agriculture. Current Science, pp. 1557-1563.

http://cgwb.gov.in/documents/AR/SUCCESS%20STORIES%20OF%20AR.html

http://lists.goanet.org/pipermail/goanet-goanet.org/2007-June/144337.html

https://www.indiawaterportal.org/articles/rwh-tale-two-successful-states

https://www.un.org/sustainabledevelopment/water-and-sanitation/

---

Rain Water Harvesting A Viable Way to Combat Water Crisis_compressed_compressed.pdf