GANGA 47th Issue | Page 8

deposition in the reservoir and leading to systems. Channel erosion of rivers has its downstream erosion of these sedimentary own set of consequences. The eroded depositional environments. While the rate of channel could create a lower water table sedimentations varies for each dam and each level in the affected area. reservoir, eventually all reservoirs develop a © Effects on Humans:- reduced water-storage capacity due to the Whilst reservoirs are helpful to humans, exchange of storage space for sediments. they may also be harmful as well. Reservoir Diminished storage capacity results in can decreased ability to produce hydroelectric mosquitoes’ particularly in tropical region power, reduced availability of water for where irrigation, and if left unaddressed, may advantage of the slow flowing water to ultimately result in the expiration of the breed. dams and rivers. Dams and reservoir require relocation of (b) Riverine & Coastal erosion:- potentially large human populations, if they As all dams, results in reduced sediments are constructed close to residential areas. load downstream, a dammed river is said to Breaking of dams due to natural disasters be “hungry” for sediment. Because the rate like earthquake may cause catastrophic of deposition of sediments is greatly reduced damage to the downstream communities. since there is less to deposit, but the rate of Dams & Reservoirs may impact on earth’s e rosion nearly constant, the water flow climate. Warm climate reservoirs generate erodes the river shores and river bed, methane, a greenhouse gas, when the threatening shoreline ecosystems, deepening reservoirs are stratified in which the bottom the river bed, and narrowing the river over layers are anoxic (i.e. they lack oxygen), time. This leads to a compromised water leading to degradation of biomass through table, reduced water levels, homogenization anaerobic processes. Hydroelectric dams are of the river flow and thus reduced ecosystem the number one source of methane gas variability, reduced support for wild life, and emissions caused by humans which impact reduced amount of sediment, reaching more to climate change than carbon dioxide. become mosquito breeding and grounds snails can for take coastal plains and deltas. This prompts coastal erosion, as beaches are unable to replenish what waves erode without the Editor- Sujit Choudhury, Published by IRBMS (© Integrated River Basin Management Society) sediment deposition of supporting river 8 Integrated River Basin Management Society