This page is meant for the Internet Users to share their views with other on the Himachal Government website.
However, the State Government neither subscribes to the views of the Internet Users nor the topics being put up on Discussion Forum.
In case, the State Government invites views on a topic of particular interest to the State for some policy formulation, it will be
specifically mentioned against the TOPIC. In every case, the views sent by the Internet Users through the interface given below will be
screened for offensive language/ material and put on this page after one week of receiving it.
Select any Topic to view the Internet Users views on that Topic. The Internet Users are also encouraged to suggest topics for this page.
Blocking the rivers\ streams by damming converts it into slow flowing lentil aquatic ecosystem. Benefits of impounding rivers are: flood control, hydro power generation, navigation, water supply, fishery etc. However, major drawbacks of damming which exists in relation to fishery are: blockage to fish migration ,efficiency of fish passes, reduction in flood plain fish production etc. Impacts of damming can be grouped into direct and indirect effects:
1) Direct Effects:-
i. Dams, weirs and barrages act as physical barriers to migrants preventing passage of fish to their usual breeding, rearing, and feeding grounds. This results in massive failure of recruitment and eventual extinction of stock. The blank niche so created may be filled by the undesirable species.
ii. Blocking results in change in physico-chemical and biological parameters upstream and downstream as well as in surrounding environment and also causes fluctuations in plank tonic, crustacean and molluscan fauna(the natural fish food).
iii. Fish passing downstream through structures at a dam can suffer mortality or damage in a number of ways including abrasion against rough surfaces, turbine blade mangling, rapid pressure changes, water shearing effects and nitrogen super saturation in the stilling basin.
2) Indirect Effects:-
i. During warm season the reservoir get thermally stratified which can result in deoxygenation of the hypolimnion. Cool and\or anoxic water discharged from the hypolimnion can severely reduce water quality downstream and negatively impact fish stock and fisheries. Fish may be eliminated from the river as far downstream from the dam as deoxygenation persists.
ii. The sediment released from the reservoir can hasten turbidity which can create severe problems for the downstream flora and fauna.
iii. Sediments trapped in the reservoir may be contaminated with pesticides and industrial chemicals from catchments sources and residues can enter the reservoir food chain and make fish poisonous.
iv. In most cases, blocking the rivers by damming result change in fish biodiversity and stock abundance e.g. auto stocking rate if fish. Usually the number of fish species decline. Stocks of long distance migrating fish species and fast flowing water species decline while stocks of pelagic species and species that prefer slow moving water increase.
v. The clearing or no clearing of trees from submergence can cause important consequences for fish production. Although drowned trees increase the food supply for fish, however trees also readily entangle fishing gears, thus decreasing the catch ability of fish. vi. Extensive deoxygenation and acidification may occur due to rotting of submerged vegetation which may result in the extensive kill of the original riverine population in the lower layers of water.
3) Reservoir And Fishery Management:-
For fishery management in the upcoming reservoir
a) pre impoundment studies shall be done aimed at collecting various information to provide framework for future development policies,
b) post impoundment management practices i.e. prevention or loss of endangered and commercially important fish biodiversity, maintenance of fish stock abundance and regular hydro biological studies of the reservoir should be carried out.
The success of management measures depends on the ability of an aqua-culturist or limnologist to identify the problems to predict both qualitative and quantitative effects of a water body.
Yes its true that fauna and flora of hill areas are very much precious and these dams and barriers are dangerously affecting our natural wealth. But, it is also true that today, to exploit natural resources is very necessary but exploitation should be in virtual way. Therefore, organized and systematic planning is very much required. Pros and cons of each and everything is here. These dams can be cause of destruction but these dams are the cut throat need of the hour.
construction of all these river projects are probably affecting our flora & fauna which is a natural charm or we can say is trademark of our state. so I would say that environment agencies and geographical agencies must be consulted before undertaking any project in himachal because we have lost a bit of our natural heritage. We all should work in a direction to save and let the himachal smile, flourish, smell, look beautiful and charming.
Emergence of River Valley Project vis-�-vis Shrinking and disappearing fishable river/ streams in hill states is right to some extent. But we all know USA, U.K. the devloped countries in the world never let these things to come as obstracle in the path of development. Its the demand of today. If we want to rise we have to compromise to some extent.
we can't let ourself thrown in the 3rd world when the world is ushering towards a new era. Being the small and remote state of india people of himachal have been cutoff from whats going around the world.
Dams, bridges, roads construction, no doubt spoils the environment, but side by side they are providing the employment to number of unemployed youth of the state too. Also this helps in bridging the gap between the people of the remote areas and the world around. Its providing electricity, water etc. If not to the concerned state but to the neighbouring states too.
In the fast pacing world can we let our people suffer because of no roads, suffer our people because of no electricity, because of no dams etc. We shout of environment but hardly think how much loss is there because of the non availability of today's needs.
can't we restore environment friendly atmosphere even after the emergence of river valley projects etc. Yes we can but it needs commitment. We have to go side by side. Nothing should be at the cost of one another. Neither eEmergence of River Valley Project at the cost of fishable river/ streams in hill states nor vice versa.
In Shivalik ranges starting from Ispur towards Hosiarpur, Gagarate there are chos that can be blocked at suitable places near the foot hills and there would be enormous water storage at every village. The small Dams can be built and all rain water stored like harvesting of water and the flooding of Sawaon [MAIN STREAM OF RAIN BASED BRIVERS] can be avioded and this stored water near foothills can be used for fish growing. I can name pandoga, loharly, there would be more such places. Dams like Gobind Sagar on very low level would be worthwhile and better than tobbas which are non existants.
Dam construction, channelization and diversion of water disrupt natural biological cycles of aquatic species viz. seasonal migration of fish & various insects with aquatic larval stage and other aquatic species as well as ethnic fauna of various riparian plant species. The denial of migration may result into permanent and irreversible reduction of fish stocks ranging from lower level of abundance to complete extermination. The niche so vacated will be later filled by coarse & undesirable species. The most radical effect is on aquatic flora and fauna from hydropower development of rivers it is usually due to reduction or elimination of the seasonal variations in water level. Considerable reduction of flow in the residual various tailing below the dam may completely dry up the fish spawning/ breeding grounds, shallow areas are formed which impede fish movements.
In Himalayan upland the development activities have threatened the existence of many species particularly native fish mahseer & schizothorax.
The blockage of fish movements upstream can have a very significant and negative impact on fish biodiversity. Many findings reveals that large no of aquatic fauna have been lost as a consequence. In the Columbia River, USA, more than 200 stocks of anadromous, Pacific salmonids became extinct.
Sturgeon populations in the Caspian Sea rely on hatcheries, mainly in Iran, since Russian dams block natural spawning migrations. Hydroelectric dams in the Amazon basin have halted the long distance upstream migration of several species of catfishes and interrupted the downstream migration of their larvae. On the Araguaia-Tocantins River basin, Brazil, several species of migrating catfish have been drastically reduced in abundance as a result of dams; catches in the downstream fisheries have been reduced by 70%. Artificial barriers also lead to the dramatic decline of the endangered cyprinid fish, Anaecypris hispanica in Iberia.
In general, a river is a one-way system for molluscs, as many molluscs can only move downstream by drifting or being dislodged by flood events and moved downstream. But some species with a larval form can move significant distances upstream with the aid of a third party, e.g. host fish during the larval stage. A single dam and more significantly multiple dams along a given river interfere with the genetic bridging function of the main stem.
Water quality, flow and seasonality of flow are not normally disrupted in the upstream area above the reservoir so impacts are generally less than for the reservoir and downstream areas. Nevertheless, the dam and the reservoir affect migratory movements of species into and out of this upstream area. The genetic exchange with downstream segments is reduced or prevented. A study was made of molluscs upstream in a braided river that enters a reservoir on the River Inn in Austria (Foeckler et al. 1991). Data shows that there was a decline of 10 species upstream of the reservoir.
In the construction of reservoirs, the clearing of vegetation, movement of earth and rock, the presence of humans and machinery, bringing in construction materials, use of explosives, noise, and reducing or cutting off river flow and increasing turbidity, will affect biodiversity. Removal of forests or other vegetation over a wide area, excavation, earth and rock movement and reduction in river flow are the most significant. Some of the on-site activities are mirrored in off-site disturbances such as the mass displacement of earth and rocks and road building. During reservoir filling the river and any associated wetland areas become inundated. Riffles, runs and pools of the river are lost beneath the rising waters, leading to the extirpation (or extinction) of habitat sensitive riverine species with tightly defined niche requirements. Fishes in rivers are generally well adapted to flowing water. Similarly molluscs are often restricted to specific habitats within the river system, e.g. some species are bottom-dwelling filter feeders, others live in weeds at the edge of the channel. The construction of reservoirs converts lotic (running) into lentic (still water) habitats. Species dependent on running water will diminish or disappear. In almost all cases, the diversity of fish species will drop (McCully 1996).
The changed or fluctuating conditions in the reservoir may lead to opportunities for weed or exotic species e.g. the water hyacinth, Eichhornia crassipe. Increases in the number of mollusc-borne diseases following dam construction in various countries. For example at least four genera of mollusc-borne human diseases have increased as a result of impoundments in Thailand (Woodruff & Upatham, 1992).
In the downstream segment, most of the impacts of a dam are negative. In a preliminary assessment of 66 case studies of the impact of dam construction on fishes, based on qualitative information, 73% of the impacts were negative and only 27% were positive. About 55% of the impacts were below the dam and linked to fish migrations and to floodplain access.
Reference: Don McAllister; John Craig; Nick Davidson; Dianne Murray and Mary Seddon. Biodiversity Impacts of Large Dams. On behalf of IUCN - The World conservation Union
River valley projects have been planned most unimaginatively. The infamous North Bihar River Project has proved to be devastating to the State. Miles long embankments, silted sluice gates, stagnation of water, rise in soil salinity has resulted in damage to agriculture, ceasation of auto stocking of fish seed in north Bihar ponds, damage to fish breeding grounds, reduction of flowing waters affecting the fish fauna and loss of biodiversity - a loss of national heritage. We should concentrate on small projects at many places, which are being planned in great hurry. We must take into account long-term effects and hold serious and prolonged brain storming sessions with hard field level evidences. Water crises have been allowed to occur causing a number of problems. Each river valley has different problems. No rule of thumb can be applied. Location specific case studies are very essential. There are no instant solutions please.