Saturday, September 6, 2003
M A I N   F E A T U R E


Why are we not harvesting rainwater?

Excessive exploitation of groundwater is a major reason for the acute drinking water shortage in many districts of Punjab and Haryana, write Vishal Gulati and Sunil Kumar

THE story of depleting watertable is being scripted by human beings themselves. It is a story of shortsighted planning, government indifference and peopleís ignorance.

Although on the face of it seems that more than 70 per cent of the earthís surface is covered by water and there cannot be any shortage of water whatsoever. But when we carefully analyse our hydrosphere, we find that 97 per cent of the water on the earth, found in oceans, is saline and cannot be directly used for human consumption. Out of the remaining 3 per cent, 2 per cent is in the form of glaciers, ice caps and moisture in the atmosphere. What actually remains available for human consumption is only 1 per cent of the total water. Out of this, about 0.66 per cent is available in the form of groundwater, and the remaining is present in the form of freshwater in rivers and lakes.

 


Since it is not possible to supply water to all places from rivers and lakes and it is relatively easier and less costly to draw water from underneath the earth surface, the dependence on groundwater has been increasing sharply, both for irrigation and human consumption. Out of these two, irrigation takes the lionís share. According to rough estimates, in 1970-71, about 41 per cent of the total irrigated area got water from canals and rivers, while 14 per cent was being irrigated by tubewells. But in 1997-78, the area under canal irrigation went down to 31 per cent, while the area under tubewell irrigation went up to 34 per cent. This was due to the reason that there is no policy that puts any price on the use of groundwater itself. Moreover, some states have been providing electricity free or at nominal charges for running tubewells. All these factors have put the aquifers under severe stress.

In the case of Punjab, Haryana and even Uttar Pradesh, the dependence on tubewells has increased immensely. In these states, the tubewell-irrigated area is about 61.6, 50.8 and 65.5 per cent, respectively, while the canal-irrigated area is only about 38.3, 48.9 and 30.1 per cent, respectively.

Excessive exploitation of groundwater is a major reason for the acute drinking water shortage in many districts of Punjab and Haryana.

The watertable in 66 per cent area of Punjab and 33 per cent area of Haryana has declined drastically during the past 25 years, say studies conducted by the Chandigarh-based Central Ground Water Board, North-Western Region.

At present, there are 16 lakh tubewells in Punjab and Haryana, says the boardís Regional Director, M.D. Nautiyal.

In Punjab, in the districts of Patiala, Sangrur and Moga, the watertable is falling at an alarming rate of about 40 cm per year. In Ludhiana and Jalandhar districts, the decline is between 30 cm and 40 cm per year, whereas in Amritsar district the decline is 20 cm per year.

In Haryana, the fall in southern parts is more than 40 cm per year, whereas in central parts it is between 20 and 40 cm per year. However, in northern parts it is up to 20 cm per year.

The situation is alarming in Amritsar, Jalandhar, Ludhiana and Karnal as there are groundwater troughs in the central parts of the cities. This has resulted in flowing of groundwater from the surrounding areas to the centre of these troughs.

The studies further reveal that the fall in watertable is more in cities than in rural areas. In the city areas of Amritsar, Jalandhar, Ludhiana, Patiala and Dera Bassi, the watertable is declining at a rate of more than 50 cm per year.

Nautiyal says over-pumping from aquifers through a large number of tubewells has caused a significant decline in the watertable. In cities, where the dependence on groundwater has increased sharply, the rate of groundwater recharge has taken a plunge. The reason being that more and more area in the cities is coming under construction, for erecting residential or commercial buildings, laying roads and pavements. This leaves little open space for the rainwater to seep in to replenish the groundwater reserves.

The board has sent proposals to the Central Groundwater Authority to declare Jalandhar, Patiala, Dera Bassi tehsil, Moga (Blocks 1 and 2), Sangrur block, Mahal Kalan block and Ahmedgarh block in Punjab as notified areas for registration of tubewells. In Haryana, Shahbad, Narnaul, Nangal Chowdhary, Samalkha, Karnal and Khol blocks have been identified as over-exploited areas. Ludhiana and Amritsar have already been declared notified areas, he adds.

In August 2002, a proposal was sent to the authorities concerned to make harvesting of rainwater mandatory in Amritsar, Jalandhar and Dera Bassi tehsil. In Gurgaon and Faridabad, it has already been made mandatory.

In Chandigarh, the shallow water level is increasing in southern sectors. In the monsoon, it reaches up to 2 m, while in northern sectors it is between 30 and 35 m below ground level.

Recent studies have suggested that rainwater harvesting is imperative for tackling the impending crises. Water can be collected on rooftops, compounds, rocky surfaces, hill slopes or artificially prepared impervious or semi-pervious land surfaces.

For the common man the easiest way to tap rainwater is by rooftop harvesting. For this, one needs to channelise water to a recharge structure or a storage tank, says D.S. Saini, Senior Scientist with the board.

The harvested water in the storage tank can be used for irrigating lawns and domestic purposes. The surplus water, which cannot be stored, can be used to recharge the groundwater by adopting various artificial recharge techniques. Based on the sub-surface lithology, type of aquifer system, availability of water, depth of water-bearing zones to be recharged, different types of artificial recharge structures can be constructed.

The concept of rainwater harvesting is catching up in many states of our country, but there is a need to make it a mass movement.

Mumbai, Chennai and New Delhi have made it mandatory for builders to adopt rainwater harvesting measures. Since October 1, 2002, it has been made mandatory in Mumbai that any new building coming up on a plot of more than 1,000 sq m should have a rainwater harvesting structure. The state government is also planning to rope in owners of existing buildings in rainwater-harvesting efforts.

Under its Budget for the year 2003-04, the Karnataka Government has earmarked 50 per cent of the funds for water projects. It has also decided to introduce a Bill in the Legislative Assembly to ensure better management of water projects and schemes in the state, which has about 10 lakh borewells.

Even HUDA has made it mandatory that newly constructed buildings, with a rooftop area of more than 100 sq m, should have a provision for harvesting rainwater.

Although the design of one recharge structure may differ from that of the other, the basic principle behind all these structures is the same. Each such structure aims at collecting rainwater or other run-off by passing it through a filter arrangement and finally making it reach the aquifer.

The filter arrangement generally involves percolation of harvested water through layers of fine gravel, coarse gravel and boulders. A very important thing to be kept in mind is that the water being used for artificial recharge should not be contaminated. As rainwater is the purest form of water found in the hydrosphere, its use for artificial recharge of groundwater is recommended. Setting up of such projects is not recommended on the premises of chemical units.

It is not at all difficult to harvest rainwater; the only requirement is to understand the gravity of the situation and take some remedial measures before the situation goes out of control. The time has come to make sincere efforts to arrest the fall of watertable.