Reservoir de-siltation and its impacts on wetland water quality A case study Joseph Sebastian Paimpillil Center for Earth Research and Environment Management, K.K. Road, Cochin 17, India, psjoseph@eth.net
Introduction There is no doubt that India s water storage reservoirs are silting up and silting up at a rate much faster than either predicted at the time projects were designed and also faster than the rate that authorities are ready to accept. Silt deposits had reduced the water storage capacity in major dams by 30 40%.
Introduction 2 The governments have failed to arrest the siltation due to poor management of catchment area and not implementing the catchment area treatment as required and promised in the environment management plans of these projects.
Dam Desilting As per the preliminary estimate, the desilting could provide sand for the next 10 years. mine sand and silt from the existing water storage reservoirs behind dams to cater to the increasing demands of the construction industry. Selling the sand recovered through desilting would serve a dual purpose: revenue for the government increased storage for the dams. This can also potentially help to reduce the unsustainable mining of the riverbeds for the sand. The sand mining of the riverbeds also destroys the groundwater recharge capacity of the rivers.
Environmental impacts of dredging and removal of sedimentation According to Keri s report, roughly 30 million cu. m of sediment could be removed from an area of around 15 sq. km. (Malampuzha Dam) The desilting of the dams will be carried out only after doing environmental impact studies to avoid serious environmental problems. The sand would be mined 500 m from the dam, with little impact and no damage to the reservoir. The fact that the Malampuzha dam caters to the drinking water needs of Palakkad municipality and six adjoining panchayats is another issue since any silt removal should not affect the water supply qualitatively or quantitatively. Desilting could not only increase the storage capacity of the dam but also fetch the state at least Rs 800 core through the sale of sand, extracted from the sediment.
Revenue utilization Government expected to get 3,00,000 cc of sand from Malampuzha and Chulliyar dams special provision for the development of areas around the dams as a compensation for the hardship they undergo owing to the mining and related activities. one fourth of the revenue from sand mining in reservoirs would be spent on forestation, including prevention of soil erosion in the catchment areas.
The concerns the need to ensure that the desilting does not lead to bank collapse along the rim of the reservoir, to ensure that catchment area treatment is taken on priority so that the reservoir does not get silted up fast again, to ensure that downstream river is indeed protected from unsustainable mining, to ensure the safety of the downstream river to ensure that indeed all these norms are implemented in a credible way. government must 'ensure that sand holidays are declared and enforced in the heavily sand extracted and utilised rivers for minimum five years and ensure that sand mining from the rest of the rivers follows strict scientific norms and regulations
The concerns.. the reservoirs that have over the years accumulated toxic pollutants from the agriculture, industries and towns upstream from the dams could pose the additional hazard of the silt and sand being contaminated with such toxic substances. A proper environment impact assessment would have to look at such issues. Similar is the issue of use of the fine silt that would also be part of the reservoir soil. This can be a rich manure if toxic pollutants have not contaminated it. Such rich soil should not be burned for brick making, which is a likely danger.
River Periyar Periyar is one of the biggest rivers in Kerala it is the source of drinking water for many people who live on its banks. The river Periyar is harnessed at various points in its course for generating electricity and for irrigation purpose. The hydroelectric projects across Periyar and its tributaries are: Mullapperiyar dam, Idukki dam, Idamalayar, Kallarkutty dam, Kundala and Mattuppetty dam.
Rivers and Lakes in Kerala ( South India)
Rapid Mud/Sludge deposition in Periyar river by reservoir de-siltation
Kallarkutty dam
MALAMPUZHA Dam
Dam clean-up State Electricity board of Kerala (KSEB) decided to clean-up one of its hydro-electric project dam at Kallarkutty (Periyar) without studying about the consequences: released a huge amount of sediments from the dam into Periyar The sediments had been in Kallarkutty dam for quite some time (>18 years) The Periyar is already polluted by the industries on its banks and the releasing of sediments proved to be the proverbial last straw. Though the present crisis occurred only on account of the negligence on the part of the officials supposed to clean the reservoir once in two yearsbut such cleaning was never done in the last 18 years resulting in accumulation of sludge, similar openings of the dam shutters can also occur due to heavy precipitations associated with climate changes.
Impacts of sediment discharge The water in the lower reaches of Periyar had changed into red The discoloration occurred at a Bund near Eloor which houses the Udyogamandal Industrial Estate. Due to tidal currents, the discolored water flowed upstream (Eloor is just 17 kms from the Arabian sea) Sediments got into several rural water supply pumping systems downstream. possibly affect the water supply system in the entire Kochi region. Pumping of the muddy water and distributing the same employing the traditional treatment methods using chlorine and alum seem to be insufficient for human consumption due to the presence of high impurities and discoloration.
Discoloration and turbidity It is worthy to examine the water quality changes in the river and the manner in which the 40 lakh people depending on Periyar for potable water reacted to the alarming situations of the spreading of waterborne diseases and to look into the urgent precautionary measures by the authorities. The heavy discharge triggered a color change in the river and water started getting muddier with the turbidity level in the river varied between 58 and 68 ntu (nephelometric turbidity units). Though no toxicological testing was done during this discoloration time for the residents of the region the discoloration of the river and massive fish kills are not a new phenomenon. During the last nine months, discoloration had occurred 25 times and fish kills occurred thrice. The day after the most recent discoloration due to muddy water, fish kill occurred in a neighboring village.
Impacts on turbidity levels The turbidity levels was 1 ntu before the problem began. The turbidity level in the river varied between 58 and 68 ntu. After treatment with alum and lime, the water quality level reached to the acceptable limits between 4 and 7 ntu. One anticipated after-effect of the inflow of silt and decomposed organic matter seems to be `eutrophication. Experts had estimated the time for the water to clear-up to be 2-3 months. This was one of the worst blunders to happen and an environmental catastrophe. The effects of this careless act will slowly unfold in the coming months and people have to pay a hefty price for this. Apart from the drinking water problem, there was no idea about what all will be the ill-effects of this.
Discoloured Periyar
Reactions of NGO and LAEC With the pollution in the river crossing all limits, local NGOs and LAEC after waiting in vain for some help to come by from the authorities concerned had to approach the judiciary to release water from another dam to remove the muddy water in the Periyar and to seek a direction to the government to constitute a high-power monitoring committee to take appropriate action and to release sufficient funds to meet the situationand for initiating action against the officials for their failure to carry out periodic cleaning of the dam. Growing public discontent over the muddy waters issue had forced the Government to take steps to ensure the quality of drinking water by the release of clean water from two other dams to check the increasing levels of turbidity.
Reactions of NGO and LAEC.. The voice raised by NGOs and LAEC had forced the government authorities to think about the mitigation plans to deal with dam shutter openings in the event of flooding and heavier monsoons envisaged with ongoing global warming. Growing public discontent over the muddy waters in the Periyar has forced the Government to take steps to ensure the year round quality of drinking water supplied to lakhs of Kochiites. A Cabinet sub-committee recommended the release of water from Edamalayar to check the increasing levels of turbidity in the river. The LAEC, NGOs and State Pollution Control Board are keeping a watch on the water quality level following fears that industrial units might dump toxic effluents into the river.
People's Right Declaration Convention The residents of industrial region held a People's Right Declaration Convention at Eloor for asserting their right to live, food security, safe water and healthy environment. The People's Charter of Demands adopted at the convention called for immediate implementation of an integrated and comprehensive process for decontamination of the river and the surroundings It also called for issuing medical cards to all those affected for free medical aid; stoppage of production of DDT and endosulfan by the public sector Hindustan Insecticides Limited (HIL) and payment of compensation by the Centre government and World Health Organization (WHO), as the government had set up the HIL on a request by the WHO. While the sale and use of endosulfan are banned, production is not. The convention-attended by politicians, trade union leaders, legislators, scientists and environmental activists
14 point action plan of LAEC The Kerala State Pollution Control Board (KSPCB) and LAEC proposed a 14-point action plan to police the river and to check dumping of chemical effluents. These included: setting up of an online water contamination monitoring system on the lines of the one set up for Philips Carbon company to monitor air pollution building of roads along the banks of the river in the industrial area provision of a speedboats to patrol the river the setting up of a common effluents treatment plant for the nearly 200 small-scale industries in the Edayar area.
Save Periyar initiative and River Protection Authority The State Government is planning to launch a `Save Periyar' initiative after consultations with all the stakeholders and users of the river including local residents, environmental activists and nongovernmental organisations Apart from officials of the departments concerned and technical experts, people concerned about the current health of Kerala's longest river will be invited to express their views and suggestions. The Government wants the campaign to be a coordinated effort with the involvement of all sections of people affected by the plight of the river. A River Protection Authority with the powers to prosecute river abusers, was on the anvil under Water Resources Ministry.
Participatory scheme for protection of river Encouraged by the success of community involvement in river protection programmes in the country the Kerala state government proposes to involve local people in restoration of the Periyar. The Government is setting up an independent river authority for the Periyar. Under the proposed plan, Local residents, fishermen and farmers would be encouraged to monitor the river to spot incidents of pollution. Local residents would be appointed as environmental surveillance wardens.
Action plan As a part of the action plan, a survey of the river basin would be carried out to find sewage outlet points. The plan of action also included a proposal for consistent monitoring of ambient water quality and steps to restore fish habitat found in the Periyar. Aforestation programs are also introduced in the catchment s areas to maintain the summer flow in the river and also to increase the flow rate throughout the year. Under this program, trees and riverine vegetation be increased with aforestation program along the riverbank and stonewalls of the banks to be replaced with natural vegetation.
Conclusions The de-silting in any reservoir in the region is to be carried out only during the south west monsoon times as the water flow in the rivers would be high, the silt would get flushed down to the sea quickly. The environmental groups and many others have been vociferous against large dams and wanted only small local water harvesting structures to harness the monsoon flows. However the storage requirements indicate that even to hold half of the available monsoon flows (i.e. about 30 bcm), at least a million tanks would have to be in position. But, when the rains fail, these tanks submerging about two million hectares would also dry up, negating the very purpose for which they are built. Hence a combination of major, medium and minor storages has to be further constructed to utilize the available monsoon flows.
Conclusions The Local Area Environment Committee (LAEC) set up for restoring the life of the Periyar River worked satisfactorily in its initial period. It had audited many industries on the river banks and identified the illegal effluent discharges into the river. The Pollution control board on the advice of the LAEC had given instruction to the industries to install proper treatment facilities or close down the industries. But it was not achieved as the court had stuck down the order on certain legal formalities.
Conclusions The Kerala government proposal to desilt the reservoirs for sand mining, if successful, can then open up the potential to make the desilting of the reservoirs an economically viable activity for providing sand for justifiable demands. It has the potential to provide a useful example for reservoirs all over India and possibly elsewhere.
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