rivers are losing water storage capacity why (10 standard)
Answers
Answer:
Changes in weather cause the natural flow of streams and rivers to vary greatly with time. Periods of excess flows and valley flooding may alternate with low flows or droughts. The role of water-storage reservoirs, therefore, is to impound water during periods of higher flows, thus preventing flood disasters, and then permit gradual release of water during periods of lower flows. Simple storage reservoirs were probably created early in human history to provide water for drinking and for irrigation. From southern Asia and northern Africa the use of reservoirs spread to Europe and the other continents.
Reservoirs ordinarily are formed by the construction of dams across rivers,but off-channel reservoirs may be provided by diversion structures and canals or pipelines that convey water from a river to natural or artificial depressions.
When streamflow is impounded in a reservoir, the flow velocity decreases and sediment is deposited. Thus, streams that transport much suspended sediment are poor sites for reservoirs; siltation will rapidly reduce storage capacity and severely shorten the useful life of a small reservoir. Even in larger reservoirs, sedimentation constitutes a common and serious problem. Because removal of the deposited sediments from reservoirs is generally too costly to be practical, reservoirs on a sediment-laden stream are characteristically planned to provide a reserve of storage capacity to offset the depletion caused by sedimentation. Despite this, the life expectancy of most reservoirs does not exceed 100 years at present sedimentation rates.An associated problem is erosion of the stream channel below a reservoir when water is released. Because the sediment load is deposited in the reservoir, the released water has renewed transporting capacity, and channel erosion results.
Explanation:
Answer:
Factors responsible for loss of river water are:
1. ground water loss
2. agriculture
3. conversion of forests into farmland
4. climate change
Explanation:
There are so many factors responsible for the water losses in river but the most significant factor is agriculture.
- Crops require large amount of water from the river and it is then lost through evaporation.
- The second factor responsible for the water loss of the river is groundwater status. Groundwater in India is deteriorating at an alarming rate. According to the data of 2011, 30% of the India's district showed over-exploited groundwater status. Ground water nourishes rivers but when it is lost river recieves no nourishment and hence dries up. Furthermore, when the groundwater is lost, the river water seeps into the earth which results in further loss of river water.
- Another reason is the conversion of forest into farmland or wasteland. As a result, the earth absorb less rainwater and the rain that falls on the ground evaporate immediately.
- Climate change is also one of the factor. with the increase in temperature, there is increase in river water evaporation.