Grow trees to make check-dams work
The drought has given a rude jolt to the Gujarat government and the people, for them to wake up from the slumber of neglecting water and other natural resources. The recent statement by the minister of water resources Narottam Patel, claiming to have constructed 10,000 check-dams is not an achievement that one should be proud of.
The construction of check-dams across any rivulet requires careful technical planning and design. Taking into account the slope, run-off, type of soil and vegetation and the biotic influence in the catchment area is important while designing any check-dam. The news item that in next 50 days, 2,000 check-dams are to be constructed in Rajkot district, appears to be a tall order.
The hurried construction of a check-dam without proper compacting of soil, improper design of spill-way, failure to ensure safe delivery of excess water, may all cause unnecessary expenditure of time and money since the aim of the effort may not be realised. The survival rate of a check-dam is more important than the construction of a large number of them. Outright sanction of projects is fraught with the danger of wasting public money.
TO catch water where it falls is the slogan to be followed. There is no doubt that check-dams have proved their efficacy' but not without treating the slopes that contribute water to the check-dam. If slopes are not treated, the check-dam would fill with silt in one or two good seasons of rainfall.
In this, the role of trees has not been given due importance. Trees and vegetation play very important role by helping rainwater to percolate and remain in the soil. Since rainwater stops only for a short duration, the fastest means to stop water from being wasted as run-off and to maximise the rate of percolation in the soil are trees or forests.
Well-managed forests have ground water recharge and a higher water table in wells. It has been observed in experiments conducted in Europe and other countries from 1900 to this date, that run-off from forests varies from one per cent to 10 per cent depending on the type of vegetation, soil and slope. Similarly, soil loss due to erosion in well-protected forests is nil to one ton per hectare per year while it is two tons to 40 tons/ha/year.
Experiments conducted in USA and other countries confirm that without proper vegetation, it is difficult to maintain stream flows in a period when it is not raining. When rain falls, there is a need to intercept the water from running off as surface flow, then there is a need to percolate the water in the ground. Roots of trees and other vegetation can do this. It is estimated that three parts of the water is stored in soil, one part goes down to form subsurface flow and one part goes still further down to form base flow. It is actually this base flow which charges the acquifiers below the ground. Each check-dam therefore needs a good tree cover both in the upstream and downstream.
Thus it is necessary to emphasise that the number of trees in catchment of check-dams needs to be increased. This will not only ensure good ground water recharge but also ameliorate climatic conditions and provide fuel, fodder and timber.