9) Match the pro or con with the correct method for accessing fresh water. 1. fl
ID: 235983 • Letter: 9
Question
9) Match the pro or con with the correct method for accessing fresh water.
1. flood control ____________
2. generally cheaper source of freshwater than surface water ____________
3. potentially the largest resource ____________
4. most expensive in terms of energy and maintenance ____________
5. disrupts ecosystems, especially spawning fish ____________
6. Subsidence can occur if overused ____________
7. Can initially supply large amounts of water using tunnels and canals ____________
8. can greatly increase salinity of lakes or inland seas ____________
method - desalination, dams and reservoir, groundwater well, water transfer
Explanation / Answer
1. flood control _____Dams & Reservoirs_______
A- Dams & Reservoirs have the capacity to absorb the floods caused due to torrential rains in the upstream catchment area of a river albeit to a limited extent.
2. generally cheaper source of freshwater than surface water _____Groundwater well_______
A- It is easy to tap Grouundwater, especially if blessed with conducive geology (alluvial soil, soft sandstones etc) in the region of drilling. One-time investment is required and benefits last for a very long time if used sustainably.
3. potentially the largest resource ______Desalination______
A- Desalination offers the entire ocean for water usage.
4. most expensive in terms of energy and maintenance ______Desalination______
A- Desalination methods are energy intensive and expensive to maintain. Corrosion due to various types of salts of ocean damage the instruments which in turn increase the maintenance requirement.
5. disrupts ecosystems, especially spawning fish _____Dams and reservoirs_______
A- There are certain species of fishes known as Anadromous and Catadromous fishes. The former are those fishes that migrate from the oceans up the rivers to spawn and the latter are the ones which do the reverse. Salmons, lampreys, sturgeons etc are Anadromous fishes whereas American Eel, Inanga, Long fin eel are catadromous fishes. These fishes find Dams as obstacles in their life-cycle. Their spawning centres are cutoff due to this man-made structure. Some Potamodromous fishes (Inter-riverine migration for spawning) also find dams as obstacles.
6. Subsidence can occur if overused _____Groundwater well_______
A - Groundwater is filled in the minute pores of the rock formations in the sub-surface geological formations. This water exerts a certain amount of pressure (known as pore-pressure) on the overlying formations. As the water is gradually sucked out without regular recharge, the pores disappear due to overlying rock burden that enforces consolidation on the formations. This process results in subsidence.
7. Can initially supply large amounts of water using tunnels and canals ______Water transfer______
A- Water linking has the potential to transfer water from water-surplus to water-deficit regions with the help of tunnels and canals. Initially the supply is phenominal, but gradually it reduces due to water losses due to evaporation, absorption etc.
8. can greatly increase salinity of lakes or inland seas ____water transfer_______
A- Water transfer or diversion of water from one river to another or to another basin altogether has the potential to stop the fresh water supply to the water body which the river originally drained into. The best example of this is the Aral Sea where the waters of Syr and Amu Darya (Oxus & Jaxartes) have been diverted for anthropological uses. This ultimately leads to increase in salinity of the fresh-water body and its gradual disappearance.
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