Scarcity of water, methods of conservation-rain water harvesting and watershed management, ground water management

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Scarcity of water

 

Water scarcity is possibly to pose the greatest challenge on account of its increased demand coupled with shrinking supplies due to over utilisation and pollution. Water is a cyclic resource with abundant supplies on the globe. Approximately, 71 per cent of the earth’s surface is covered with it but fresh water constitutes only about 3 per cent of the total water. In fact, a very small proportion of fresh water is effectively available for human use. The availability of fresh water varies over space and time.

According to the United Nation Developement Program ,occurrence of water availability at about 1000 cubic meters per capita per annum is a commonly threshold for water indicating scarcity.

Krishna, Cauvery, Subernarekha, Pennar, Mahi, Sabarmati, Tapi, East Flowing Rivers and West Flowing Rivers of Kutch and Saurashtra including Luni are some of the basins, which fall below the 1000 cubic meter mark- out of which Cauvery, Pennar, Sabarmati and East Flowing rivers and West Flowing Rivers of Kutch and Saurashtra including Luni facing more acute water scarcity with per capita availability of water less than or around 500 cu m.

The need of the hour to change the condition of water scarity are as follows:-

  • The need to change cropping patterns based on scientific advice,
  • use of drip and sprinkler irrigation,
  • fertigation for increasing water use efficiency,
  • community participation, especially women, for better water management
  • Use of treated urban waste water to be used for farming in the adjoining areas
  • desilting of rivers
  • recharging of rivers,
  • check dams and other water storage mechanisms.

Rain water harvesting

 

Rain water harvesting generally means collection of rain water. Its special meaning is a technique of recharging of underground water. In this technique water is made to go underground after collecting rain water locally, without polluting the same.

Rain water harvesting is a low cost and eco-friendly technique for preserving every drop of water by guiding the rain water to bore well, pits and wells. Rainwater harvesting increases water availability, checks the declining ground water table, improves the quality of groundwater through dilution of contaminants like fluoride and nitrates, prevents soil erosion, and flooding and arrests salt water intrusion in coastal areas if used to recharge aquifers.

Rainwater is relatively clean and the quality is usually acceptable for many purposes with little or even no treatment. The physical and chemical properties of rainwater are usually superior to sources of groundwater that may have been subjected to contamination. Rainwater harvesting can co?exist with and provide a good supplement to other water sources and utility systems, thus relieving pressure on other water sources. Rainwater harvesting provides a water supply buffer for use in times of emergency or breakdown of the public water supply systems, particularly during natural disasters.

Watershed management

 

The term watershed refers to a “contiguous area draining into a single water body or a water course” or “it is a topographical area having a common drainage”. This means that the rainwater falling on an area coming within a ridgeline can be harvested and will flow out of this area thorough single point. Some refer it as a catchment area or river basin.

Watershed management is an efficient management and conservation of surface and groundwater resources. It involves prevention of runoff and storage and recharge of groundwater through various methods like percolation tanks, recharge wells, etc. However, in broad sense watershed management includes conservation, regeneration and judicious use of all resources – natural (like land, water, plants and animals) and human with in a watershed.

Integrated Watershed Management Programme  is to restore the ecological balance by harnessing, conserving and developing degraded natural resources such as soil, vegetative cover and water.  The outcomes are  prevention of soil run-off, regeneration of natural vegetation, rain water harvesting and recharging of the ground water table.  This enables  multi-cropping and the introduction of diverse agro-based activities, which help to provide sustainable livelihoods to the people residing in the watershed area.

The main benefits of watershed management are:-

  1. Supply of water for drinking and irrigation.
    2. Increase in bio-diversity.
    3. Loss of acidity in the soil and free for standing water.
    4. Increase in the agricultural production and productivity.
    5. Decrease in the cutting of forests.
    6. Increase in the standard of living.
    7. Increase in employment.
    8. Increase in personal get together by participation of local people.

Ground water management.

 

Scientific management of ground water resources involves a combination of

  1. A) Supply side measures aimed at increasing extraction of ground water depending on its availability and
  2. B) Demand side measures aimed at controlling, protecting and conserving available resources.

The rainfall occurrence in different parts of India is limited to a period ranging from about 10 to 100 days. The natural recharge to ground water reservoir is restricted to this period only and is not enough to keep pace with the excessive continued exploitation. Since large volumes of rainfall flows out into the sea or get evaporated, artificial recharge has been advocated to supplement the natural recharge.

Ground water resources management requires to focus attention on the judicious utilization of the resources for ensuring their long-term sustainability. Ownership of ground water, need-based allocation pricing of resources, involvement of stake holders in various aspects of planning, execution and monitoring of projects and effective implementation of regulatory measures wherever necessary are the important considerations with regard to demand side ground water management.

 

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