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Mylaram Narayana Swamy (MyNaa Swamy )
Social Scientist & Author
No:8,TTD Quarters , Near III Choultry
TIRUPATI - 517 501 A.P. INDIA
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STANDARD DEFINITION OF RAINWATER HARVESTING
The term ‘rainwater harvesting’ appears to have originated from the word ‘harvesting’, used to cover all agricultural activities involving cutting, reaping, picking and gathering of grain of value from any fully-grown crop. Rainwater harvesting may be defined as any human activity involving collection and storage of rainwater in some natural or artificial container either for immediate use or use before the onset of the next monsoon. Runoff farming, microcatchment farming and contour catchment farming are some examples of rainwater harvesting used in irrigation. underlying principle of rainwater harvesting is to ensure direct use of most of the rainfall, this is achieved in certain natural catchments or modified existing catchments to produce maximum surface runoff and minimum evaporation, transpiration and infiltration.
Rainwater harvesting as defined above was followed both at individual and community levels in most countries including India from times immemorial to obtain high-quality water for domestic, agricultural and other uses. The best example of rainwater harvesting comes from the house at Porbandar in Gujarat where Mahatma Gandhi (the Father of the Nation) was born. The terrace on the top floor of that house, thoroughly washed before the first monsoon showers, served as the rainwater catchment and an underground reservoir with a capacity of around 91 cubic metres served to store water for drinking and other domestic purposes throughout the year, while a pipe having a heap of lime at its mouth served to convey filtered water from the terrace into the reservoir.
The ancient rainwater harvesting methods of water supply declined in most parts of the world when the civilised governments in most countries including India took over the self-appointed task of supplying centralised and energised systems of piped water from long distances. Despite this, rainwater harvesting continued to exist at some places all over the world, including Israel, Caribbean, Middle East, Australia and Japan.
There has been however a revival of rainwater harvesting all over the world around 20 years ago through the dedicated efforts of certain committed individuals, private companies, institutions and professional associations because of various reasons such as, higher incidence of drought, increased population, increased pollution of both surface water and groundwater bodies, and high cost of piped water supplies. Although India has also taken a very active lead in rainwater harvesting in recent years, no much water for direct use could be obtained through those practices owing to a tendency to give priority for taking up various other water conservation and management practices including groundwater recharging in the name of rainwater harvesting. The only exceptions are with the states of Mizoram and Lakshadweep, where there was a long tradition for such practices. There has been however some effort going on to take up rainwater harvesting even in several other parts of India on a very small scale by some committed individuals, architects and funding agencies, which knew the real value of rainwater harvesting as revived in the rest of the world. People particularly from several places in Rajasthan and Gujarat have realised the need to revive their age-old traditional rainwater harvesting systems as standby sources of water supply whenever centralised water supplies failed to provide adequate water (Agarwal et al., 2001).
The credit for the first definition of rainwater harvesting comes from the high-level committee and a working group comprising of experts from various organisations all over India appointed by the National Drinking Water Mission (NDWM) of the Department of Rural Development, Ministry of Agriculture, Government of India (NDWM, 1990). As per that, the term ‘water harvesting’ refers to collection and storage of rainwater and also other activities aimed at harvesting surface water and groundwater, prevention of losses through evaporation and seepage, and all other hydrological studies and engineering interventions aimed at conservation and efficient utilisation of the limited water endowment of a physiographic unit such as a watershed or geomorphic basin.
The credit for the second definition of rainwater harvesting comes from the Central Ground Water Authority (CGWA), which was established by the Government of India in 1997 to regulate and control groundwater development and management in India, besides taking care of the alarming decline of groundwater levels. It has launched through its official website www.cgwaindia.com vigorous movement involving all water users including ordinary citizens, industries, offices, hotels, educational institutions and hospitals to take up groundwater recharging by letting roofwater to quickly reach the aquifer through abandoned dug wells, abandoned/running hand pumps, recharge pits, gravity-head recharge wells, recharge shafts, defunct bore wells and trenches/pits around injection wells. This movement has gained such a momentum in recent years that people started believing that rainwater harvesting is nothing but groundwater recharging and disbelieved that rainwater could be collected and stored for some direct use such as drinking. Extensive research work has been taken up by voluntary and research organisations and private companies on topics such as first flush systems to improve the quality of rooftop water injected into wells to prevent contamination of groundwater and to improve the quality of existing groundwater.
The government departments, which are concerned with the supply of domestic water to urban and rural areas, should have encouraged people to develop a standby source of water supply through rainwater harvesting to take care of any water deficiency caused by inadequacy or failure of their centralised water supply systems. But these agencies also advocated the use of rooftop water for groundwater recharging despite people not getting any direct water when there is deficiency of water from the centralised water supply. Pending legislation by the central and state governments, many of the authorities of the city councils have started issuing permits for construction of new houses only if the building plans incorporated provision for using rooftop water for groundwater recharging. Advocacy institutions such as the print and electronic media, industrial and business houses, and non-governmental organisations including certain clubs have been making an all out effort to popularise use of rooftop water for groundwater recharging.
People’s participation in groundwater recharging on a large scale has its own problems. Most of such structures were taken up more as a ritual rather than to really augment groundwater. Groundwater in India particularly in urban and industrial areas has been already heavily polluted owing to untreated wastewater joining groundwater. There has been already a high incidence of water-borne diseases owing to drinking contaminated groundwater. If non-technical people are allowed to take up groundwater recharging on a massive scale, there can be further deterioration of groundwater quality leading to a still higher incidence of water-borne diseases. For example, the high incidence of fluorosis in India has been traced to groundwater picking up appreciable fluoride from rocks and soils under conditions of high alkalisation caused due to mismanagement of water (Jagadiswara Rao, 1976). Outbreak of polio in over a hundred children has been reported near Ratlam in Madhya Pradesh due to drinking contaminated water from a bore well around which a large pit was constructed to artificially recharge groundwater (Personal communication from Dr. R.K. Jain, 2001).
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