Rain Water Harvesting

WATER CONSERVATION THROUGH RAIN WATER HARVESTING

The undulating terrain of Jharkhand provides excellent opportunities for Rain Water Harvesting and its conservation for use after monsoon. Storage of rain water may be on the surface in form of water reservoirs or underground – which call ground water recharging. Storing rain water underground has many benets. For example- it does not evaporate, it does not submerge surface area, it is least affected by surface pollutants like human and animal excreta and nally it is available on decentralized pattern at low cost. Water is the most precious gift of nature for survival of all living beings and a crucial commodity in new development. Only a fraction of total water on earth is fresh and accessible for us.

WATER WEALTH DISTRIBUTION

Water on earth -1.4 million cubic kilo-meter. It's distribution :
  • In the form of ocean 97%
  • In the form of Ice caps 2%
  • Fresh water (Surface + Under ground) 1%

DISTRIBUTION OF 1% FRESH WATER

  • 80% goes to sea
  • 20% for various uses
Further – distribution of 20% Fresh Water :
  • 80% for irrigational use
  • 20% for domestic, industrial and other minor uses.

Inform of surface water only 0.052% of total water wealth is available on earth-which is facing threat of water pollution. Thus human life is in danger.

CAUSES OF WATER CRISIS

  • Fresh water sources are being heavily exploited to meet the ever increasing demand of urban population.
  • Rapid urbanization reduce the availability of open surface for natural recharge of rain water.
  • Failure of monsoon makes the situation worse. Dependence on ground water increase during low rainfall
  • Large scale extraction results in depletion of water table and nally the wells become dry.

SOLUTION TO THE WATER CRISIS

  • Rain water is the ultimate source of fresh water.
  • Potential of rain meet water demand is tremendous
  • Rain water harvesting helps to overcome water scarcity
  • To conserve ground water –the aquifers must be recharged with rain water. Rain water harvesting is the ultimate answer

CONCEPT OF RAIN WATER HARVESTING

The only permanent source of water that is available to human kind today is conservation. The days of wasteful ow of water are over. Now is the time to reduce, recycle and reuse. Rain Water Harvesting is a simple, economical and eco – friendly technique of preserving every drop of water by guiding the rain water for its storage for further use. Use of rain water, resource of water supply, is probably the only source that will gain more and more importance in the coming years. Rain Water Harvesting is neither a costly process nor a cumbersome constructional scheme. It is neither energy intensive nor labour intensive. It can be cost – effective and alternative to other water accruing methods, such as desalination of sea water and diversion of rivers. Rain Water Harvesting builds inland water tables. Rain Water Harvesting will also increase the soil moisture content which will make the soil fertile and hence, conducive for agriculture, water availability, controls human concentration and growth of industrialization. At the same time excessive w i t h d r a w a l s o f g r o u n d w a t e r r e s u l t i n environmental imbalance. The conjunctive use of surface water, ground water and rain water is the need of hour. As huge quantity of rain water nds its way ultimately to sea through canals and rivers, the only alternative is to harvest and conserve this precious gift of nature by implementing Rain Water Harvesting Schemes.

Eminent meteorologist, Shri P.R.Pisharoty point out that in most parts of the country, there is a precipitation during not more than 50 days. Even on days when rainfall does occur, it does not fall over the entire period of four hours. Heavy showers of short duration are common. Most of the places of the country therefore receive rainfall for just 100 hours in a year. The remaining 8660 hours in a year, there is no rain. Therefore, if the rain is not harvested in those 100 hours, in a year when it fall in these few hours, when the river and streams swell up, then there is little water to capture to meet human need.

Every time in rainy season only about 5 – 20% of the total rain is recharged into the ground depending upon the terrain, top soil condition, subsurface formation, rainfall pattern etc.

The top soil can hold only a fraction of water that falls on it and the rest gradually percolates down, depending on the type of soil and joins the aquifers. In such case looking to rocky terrain – steep slopes and undulating topography – of Jharkhand – maximum 5 to 10% total rain is recharged in to the ground. When the rain is falling at very slow rate without impact, mostly all water is inltrated in ground. In case of heavy rains by impact less quantity percolates in ground and more water goes as run – off to the streams. Inltration directly depends on the porosity of the soil. If the soil is more porous and has more percentage of sand more will be inltration. On the other hand if the soil is of clayey nature with the ne particles, less will be inltration. It should be noted that porosity in percent is not as important as the size of pore.

In addition to above – the top cover of soil is very important, because it protects the soil from the compaction by rain and detains rainwater for more time, there will be more inltration. Therefore, the inltration depends on the density of cover. If there is dense forest on the top of soil it will detain rain water for more time. Similarly roots of trees make the soil porous. The percolating water passes downward until it reaching impervious stratum. After reaching impervious stratum it begins to move in a lateral direction towards some out let. The entrance of rainwater in to ground is known as inltration and the movement of water after entrance is known as percolation. Similarly precipitation may be dened as the fall of moisture from atmosphere to the Earth surface in any form – such as rainfall, snow fall etc.

The entire phenomenon of Hydrology is well explained in the water cycle in Map No. - 1. Whereas conned and unconned aquifers is shown Map No– 2. Before designing Rain Water Harvesting System for any project the all factors as mentioned above should be kept in mind. Rain Water Harvesting is the only feasible solution to solve the water crisis of Jharkhand.

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