Read the passages given below carefully and answer the questions that follow:
Water plays a versatile role in the functioning of the biosphere. The water cycle has two distinct branches – the atmospheric branch and the terrestrial branch. In the atmosphere, water exists mainly in gaseous form. On the earth, liquid forms and solid forms (ice/snow) predominate.
Water is important to the biosphere in that it is from water that the biosphere draws its most, abundant element, hydrogen. Hydrogen in the form of carbohydrates constitutes a very important source of energy for all living things. Although we have a plentiful supply of water in the oceans, it is not of direct use to use. We have to depend upon a small stock of water - less than $1\%$ - contained in our rivers and fresh water lakes and in the subsoil. Even this small proportion can cause havoc to life if it is not properly managed: the reference here is to floods.
While relief measures are undoubtedly important, attention has to be focused on long-term flood control measures. In the past, we had constructed flood moderation reservoirs across catchment’s areas of rivers, and built $19,260$ km of embankments and $27,850$ km length of drainage channels. Besides $18,900$ villages have been raised above the flood level up to March $1997$.
The fact is that long-term flood control measures, to be effective, should include both traditional methods and a forestation measures. The intensity of floods may be reduced by keeping the drainage channels clear and removing the accumulated silt from reservoirs and riverbeds. In fact, the dams built have trapped silt coming from the hills and prevented its large accumulation in riverbeds downstream. Hence the new emphasis on building more dams in the northern rivers should be welcomed. The embankments also need to be reinforced. In many places, they are just made of mud and sand and easily breached by a little gush of water. Other improvements should be in the regulation of water discharge from filled reservoirs and in the flood forecasting system. Even the present warning system, though inadequate, has helped to save many valuable lives and property. Since the states have been lethargic in implementing flood control schemes and since most rivers flow through many states, it would be better if flood control is handled by the Centre. The mighty Himalayan rivers are unlikely to be tamed unless we have a basic understanding as to how floods originate. Since $1947,$ Indian and foreign scientists have been repeatedly emphasizing that the volume of water in the Himalayan rivers in the monsoons is the combined effect of rainfall, snow melt and glacier discharges. Even the first expert committed set up by Nehru had opined that a serious study of the snow melt and glacier discharges is essential for avoiding flood disasters in the north. But efforts in this direction during the last $50$ years have been very inadequate. Now that satellite pictures are available detailing the snow-cover in the Himalayas over large areas it would do well to initiate measures to obtain the relevant data from such pictures. Field studies in the Himalayan region would also help flood control measures.
The author welcomes building dams in the northern rivers because they:
- Prevent trapping the silt coming from in hills
- Store water for power generation
- Store water for irrigation
- Store water for navigation