Dr Mandeep Singh Azad, Dr Manmeet
Even as moderate to heavy rainfall on Monday brought relief from the scorching heat, cloudbursts in different parts across Jammu and Kashmir triggered flash floods causing damage to residential houses and crops. Meanwhile, a cloudburst in Chuntwaliwar area of Lar in central Kashmir’s Ganderbal district in the wee hours on Monday triggered flash floods causing damage to several residential houses and roads. The irrigation and drainage system in the area has also been affected.As many as nine families were evacuated from Kalka Colony of Jammu City after their houses were partially damaged by the flash flood triggered by heavy rains.The flash floods wreak havoc across Jammu city damaging houses, boundary walls, uprooting roads, a bridge and submerging police post, Government Primary Health Centre, a tube well in low-lying areas at Gadi Garh falling in Satwari area. Water in our country follows its own rules sometimes affecting lives because of no or low water availability and sometimes it is flooding. Every year agriculture production is affected either by increased or no rains. It is very important to come up with some technologies and initiatives to use the rain water for use so that this natural and most essential resource can be exploited fully.Monsoon rains that meet nearly 80 percent of India’s water needs arrive only in June. Large parts of the country face water shortage in summers from March till May. The country’s dams can store only 200 cubic meters per person of water, according to a World Bank report. That compares with 5,000 cubic meters in the U.S. and Australia, and 1,000 cubic meters in Mexico and China. India can store only about 30 days of rainfall, compared with 900 days in major river basins in arid areas of developed countries.Rainfall deficiency has been accumulating over the last few seasons, due to which the temperature will be running above normal.
Of all the water in the world, only 3 percent is fresh. Less than one third of 1 percent of this fresh water is available for human use. The rest is frozen in glaciers or polar ice caps, or is deep within the earth, beyond our reach. To put it another way, if 100 litres represents the world’s water, about half a tablespoon of it is fresh water available for our use.As our population grows, more and more people are sharing this limited resource. Also, the more water consumed the less there is available for the environment. Therefore, it is important that we use water wisely and do not waste it.Water is probably the most important substance for preserving life. In fact, scientists looking for evidence of life on other planets regard the presence of water as a vital clue. In developed nations we tend to take water for granted because it flows easily out of the tap. But we are rapidly depleting the global supply of fresh water, and this reality could potentially have dire consequences.
Despite water being an existential need for humans, it’s also one of the most under prioritized but over abused commodity. Water is central to our lives but has not been the central point of focus in our planning while we rapidly evolve into an urban society. India world’s oldest civilization grew around the Indus and the Ganges and is still thriving. But not for long. Post-independence, due importance was given to harnessing the power of water by way of controlling and storing of water through large Dams. That was the need of the hour. However, our cities and towns have subsequently grown without planning for water need vs water availability.
In rural areas, rain water harvesting is taken up considering watershed as a unit. Some of the simple techniques which can be used in villages for water harvesting are:
Gully plug-Gully plugs are built using local stones, clay and bushes across small gullies and streams running down the hill slopes carrying drainage to tiny catchments during rainy season.Gully Plugs help in conservation of soil and moisture.
Contour bund-Contour bunds are effective methods to conserve soil moisture in watershed for long duration.These are suitable in low rain fall areas where monsoon run off can be impounded by constructing bunds on the sloping ground all along the contour of equal elevation.
Gabion structure-This is a kind of check dam commonly constructed across small streams to conserve stream flows with practically no submergence beyond stream course.A small bund across the stream is made by putting locally available boulders in a mesh of steel wires and anchored to the stream banks.
Percolation tank-Percolation tank is an artificially created surface water body, submerging in its reservoir a highly permeable land, so that surface runoff is made to percolate and recharge the ground water storage.Percolation tank should be constructed preferably on second to third order steams, located on highly fractured and weathered rocks, which have lateral continuity down stream.
Check dams / cement plugs / nala bunds-Check dams are constructed across small streams having gentle slope. The site selected should have sufficient thickness of permeable bed or weathered formation to facilitate recharge of stored water within short span of time.The water stored in these structures is mostly confined to stream course and the height is normally less than 2 m and excess water is allowed to flow over the wall. In order to avoid scouring from excess run off, water cushions are provided at downstream side.
Recharge shaft-This is the most efficient and cost effective technique to recharge unconfined aquifer overlain by poorly permeable strata. Recharge shaft may be dug manually if the strata is of non-caving nature. The diameter of shaft is normally more than 2 m.
Dugwell recharge-Existing and abandoned dug wells may be utilized as recharge structure after cleaning and desilting the same.The recharge water is guided through a pipe from desilting chamber to the bottom of well or below the water level to avoid scouring of bottom and entrapment of air bubbles in the aquife
Ground water dams or sub-surface dykes-Sub surface dyke or under-ground dam is a subsurface barrier across stream which retards the base flow and stores water upstream below ground surface. By doing so, the water levels in upstream part of ground water dam rises saturating otherwise dry part of aquifer.The site where sub-surface dyke is proposed should have shallow impervious layer with wide valley and narrow out let.
Dr Mandeep Singh Azad, Dr Manmeet