Large Dams, barrages, reservoirs and canals

Dams have often been regarded as man’s response to nature’s vagaries, to mitigate flood and drought by containing water and releasing it as per demand and supply. Lately, dams are seen more as hydropower generators with flood mitigation, irrigation and drinking water supply only being additional benefits. This can be because of the increased acceptance that dams and canals, as awe inspiring as their structures might be, fail to deliver water to more than half of their commands. However, data and experience tell us that even the hydropower generation is also falling way below the promised numbers.

History and extent of dams in India

India’s first dam is the Kallanai built on the Cauvery river by King Karikalan of the Chola dynasty around 2,000 years ago. The dam, which is still functional and irrigates millions of acres, spans 329 m in length and 20 m in width. However, it was only post-independence that India’s love for big dams became more intense with the commissioning of a slew of projects including the Hirakud (1957), Gandhisagar (1960), Bhakra-Nangal (1963) and Nagarjuna Sagar (1967). Since then, the country has been continuously working on reining in its rivers for want of power, irrigation and domestic and industrial water supply needs. Almost half of the large dams in the country were built in the two decades of 1970-90. Maharashtra has the maximum number of large dams in the country (1845) followed by Madhya Pradesh (905) and Gujarat (666).

Map of major dams in India

A multi-purpose dam project includes one or more dams, infrastructure for generation of hydropower, infrastructure for housing of workers and for offices, a distribution network of canals and pipe systems, and access roads. All these have their individual and cumulative impacts on the river and the surrounding environment. Here also lies an opportunity to minimise the 'collateral damage' caused by dam projects by minimising the footprint of these adjuncts.

Dams as power generators

Hydropower is often billed as a renewable, economic and non-polluting source of energy and hence there is an increased emphasis on building dams especially in the hydrologically-rich but geologically-fragile Himalayan states. An assessment study put the hydroelectric power potential of the country at about 84,000 MW with maximum schemes envisaged on Brahmaputra basin (226) followed by Indus basin (190) and Ganga basin (142).

Possibility of revenue generation through sale of power units to other states and private players remains the main draw for state governments to invite project developers. However, reports suggest that poor financial conditions of discoms make it a poor proposition. Average generation per MW of hydro capacity in India in 2014-15 was over 20 per cent less than that in 1993-94.

Dams and canals for irrigation

Canal system of irrigation had been prevalent in India for centuries but it was the Ganga Canal that laid the foundation for large scale diversion of water to farms.

Number of dams in various statesThough the work was undertaken under the leadership of British Colonel Proby Cautley, it was the traditional acumen of local villagers that made the vast network possible. The canal was commissioned in 1855 irrigating around 5,000 villages. Today, the system irrigates nearly 9,000 km² of agricultural land in 10 districts of Uttar Pradesh and Uttarakhand.

The start of the Green Revolution in the mid 1960s put the spotlight on canal irrigation as the new hybrid crop varieties bred on heavy dose of chemical fertilizers and pesticides demanded assured irrigation. However, the increased investment and network expansion dealt little benefits. The World Commission on Dams in its year 2000 report found that the contribution of large dams to increased food grains production in India was less than 10 percent.

Loss in seepage, huge demand-supply gap, diversions under political pressures and comparatively easier and local availability of groundwater through pervasive use of borewells are the reasons for decline in efficiency trend.

Between 1996-97 and 2002-03, the area under canal irrigation declined by 2.4 million ha (13.8 per cent), the area under tank irrigation fell by 1.4 million ha (42.4 per cent), and the area irrigated by all other sources declined by 1 million ha (28 per cent). The only irrigation source that increased its share was groundwater wells, by 2.8 million ha (more than 9 per cent).

A study of 210 major and medium irrigation projects by SANDRP used the data supplied by the Ministry of Agriculture to show that after investing Rs 130,000 crore, these delivered 2.4 million ha less irrigation during 1990-1 to 2006-7. This means, the governments have to invest twice as fast in canal irrigation projects every year just to keep their command areas from shrinking

The study said that around Rs 1,00,000 crore was wasted in the name of improving irrigation. Feasibility studies were fudged in the case of most of the projects with huge investments, over-optimistic predictions were made and very little money was earmarked for basic maintenance such as desiltation. In some cases, political interests ensured that water was diverted to unviable areas at the cost of needier regions.

Dams and flood control

The efficiency of dams to withhold floods has always been put to question. Critics have also termed dams as harbinger of floods claiming that the essential scientific assessment for consistent release of water to avoid build up is rarely done.

Absence of a standard operating procedure for releasing water from the dam gates was evident in 2014 when 24 students picnicking in a river were swept away due to sudden release of water from Larji dam in Himachal Pradesh

Similarly, area downstream of Hirakud dam in Odisha has witnessed 14 floods in recent past with nine caused by sudden release of water from the dam. A major reason is that the dam has not changed its flood control strategy for 23 years while the rainfall pattern has undergone major changes in local areas. Lack of a coordination mechanism between neighbouring states about water flow also leads to emergency situations like one in 2011 when sudden release of water flow from upstream dams in Chhattisgarh led to breaching of danger mark in Hirakud.

In Gujarat, sudden release of large quantities of water from Ukai dam led to the biggest flood of 34 years in Tapi river submerging over 80 per cent of Surat, killing 150 persons and stranding over 20 lakh. Similar examples have been reported from other states.

Problem with 'training rivers'

Dams cause a disruption in the flow of a river by transforming it into a series of pools separated by dry stretches. The environmental impacts can be felt on the landscape, water resources, forest cover, and biodiversity. The Himalayas are almost equally distributed between zones 4 and 5. While a series of dams are being constructed in a seismically vulnerable and ecologically fragile zone, not only is optimisation of the planned development not considered, but the cumulative effects of the dams also are not considered. On a local level, blasting increases the possibility of landslides, and causes air and noise pollution. Quarrying on hill slopes and in the riverbed causes pollution and destabilisation of the slopes.

The large scale construction that is an inescapable part of hydropower development leads to deforestation. It has been observed that construction leads to the inadvertent loss of much more forest than has been accounted for. The presence of a dam on a river also impacts the ecosystem by bringing about a drastic change in the species composition. Invasive species tend to appear and flourish while suppressing endemic species and even causing some to become extinct. 

An affidavit filed by Ministry of Environment and Forest in the Supreme Court admitted the role of hydropower projects in Uttrakhand disaster in 2013. It said that “the maximum damage sites in the disaster affected areas (were) located either upstream or immediately downstream” from hydropower projects.

According to a paper by the United Nations Environment Programme, dams and their associated reservoirs permanently impact on freshwater biodiversity by several processes. Climate change has also been linked with dams. Studies show that large dams cause anoxic decomposition which leads to the formation of methane gas. This ‘greenhouse gas’ produced by dams may contribute to global warming to an appreciable extent. According to a study, dams contribute about 24 per cent of the total methane emissions in the world. Of these emissions, India contributes slightly under 28 per cent.

Submergence and displacement

Though the benefits of a dam are often exaggerated, the estimates related to land submergence and possible displacement of people are invariably kept low to paint a positive picture.

From Hirakud to Bhakra Nangal to Tehri and many more, scores of affected families were not rehabilitated at all. Those rehabilitated also complained about lack of livelihood opportunities and poor living conditions. Narmada Valley project, around which a big people's movement was built, remains the most controversial irrigation and hydropower plan. Envisaging around 30 irrigation and hydroelectric multipurpose dams, the project's environmental and social costs vis-a-vis the benefits have been cause of much debate and litigations. Sardar Sarovar dam, the largest structure on Narmada river, is believed to have displaced over 3 lakh families and is expected to displace additional 2.5 lakh families if its height is further increased by recently-approved 17 metre.

The World Commission on Dams in its report says: “While dams have delivered many benefits and made a significant contribution to human development, in too many cases the price paid to secure those benefits, especially in social and environmental terms, has been too high and, more importantly, could have been avoided.”

Political issues around dams

Shortage of water is increasingly being felt resulting in conflicts across the world. For the same reason India is facing disputes both within and outside its boundaries. While Punjab, Haryana and Rajasthan are fighting over water sharing from Bhakra Nangal, Kerala and Tamil Nadu went to court on diversion of water from Mullaperiyar dam.

On the other hand, Pakistan claimed that design of Baglihar project in Jammu and Kashmir violated the Indus Water Treaty whereas India is wary of China's plan to tame Brahmaputra waters through a series of dams. Similar are the concerns of Bangladesh which lies further downstream over India's attempt to build dams.

Way forward

It is evident that instead of focusing on building new dams, we need to attend to underperformance of existing projects. Decentralised solar, wind energy and small hydroelectricity projects with local communities as their managers as well as consumers can offer sustainable alternatives to big dams. This will not only mitigate ecological and social impacts of power generation but also reduce cost of power generation and distribution.

For irrigation purposes, revival of traditional community-managed networks like kuhls of Himachal Pradesh, phad irrigation of Maharashtra and recharging of underground aquifers through rainwater

The World Commission on Dams lists seven steps as a remedy to issues arising from dams. These include gaining wide public acceptance, exploration of alternatives to dams, optimal usage of existing structures, protection and restoration of ecosystems at river basin level, recognising entitlements of the affected people, compliance with applicable regulations and regional co-operation on trans-boundary rivers.

A few of the western countries, having realised the futility of large dams, are trying to help rivers reclaim their territory. Dams that no longer serve a useful purpose, are too expensive to maintain safely, or have harmful impacts are facing the axe especially in United States where the rate of decommissioning of large dams has overtaken the rate of construction since 1998.

The provision of adequate environmental flow releases from dams is an important means of achieving a compromise between overt exploitation of our rivers and a non-practical cessation of all use. Attempts have been made towards the assessment of these flows for the Ganga, and an ongoing project aims to achieve implementation of these flows in the Ramganga. The successful process of e-flows in India may indicate that it is going to be mainstreamed into water resource management policy.

 

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Development of operation policy for Tawa dam – A research report by National Institute of Hydrology
The study deals with the development of an operation policy for the Tawa da, Madhya Pradesh, which adopts rule-curve based policy for conservation regulation of the dam. Posted on 30 Jul, 2010 07:57 PM

The study deals with the development of an operation policy for the Tawa dam. It adopts rule-curve based policy for conservation regulation of the dam developed for three levels viz. upper rule level, middle rule level (critical for irrigation) and lower rule level (critical for water supply and upstream use). The generated simulation model developed by the Water Resources System Group at the National Institute of Hydrology is used to simulate the system operation and to refine the rule curves.

Environmental flows: Free-flowing rivers around the world
The other side of the story: Free-flowing rivers around the world Posted on 30 Jul, 2010 11:56 AM

This is the first in a new series of articles that IWP will host on various aspects of Environmental Flows. We welcome your comments and original articles for this series, please mail us at portal@arghyam.org


The other side of the story: Free-flowing rivers around the world

With around 5100 large dams, India ranks third in the world with regards to the number of large dams. The ongoing debate over the economic, social and environmental costs of large dams has indicated many times that these costs are not commensurate with their benefits. Although we have dammed all our major rivers, (except Brahmaputra and plans to dam its major tributaries are on way, some like Ranganadi have already been dammed), profoundly changing their hydrological, ecological, social and cultural systems, we are yet to form a policy which states that environmental flows in rivers are a necessity. It is more than clear now that environmental flows relate to well being of not only ‘birds and fishes’, but also of the entire human society . Take an example of fisheries, lack of flows in rivers and contractor-owned reservoir fishing has affected the livelihood of hundreds of thousands of small fishermen . Environmental flows also dilute pollution load, so let us not hide behind the fact that pollution is wiping out our riverine fish, not the absence of flows. It is also clear that environmental flows do NOT mean a decommissioning of all the present dams, nor do they mean any random figure like 60% or 10% of MAR . Eflows require reaching a wise compromise through science and local negotiations, for each river.

While many countries have put in place policies and laws for maintaining environmental flows in their rivers, there is also a rarer category: Rivers which have not been dammed yet, rivers which retain their connection from the source to the sea, nurturing myriad ecosystems and communities in their wake! These are known by many names like Free flowing rivers, Wild Rivers, Pristine/ Virgin rivers, Heritage Rivers, etc., each indicating their rare character and value. In ecological and cultural terms, the value of these rivers is immense and as more and more rivers are being dammed the world over, this value is increasing steeply. Unfortunately, in today’s economic terms, these rivers are still waiting to get their due recognition, but as human systems evolve, they will surely be seen as ‘invaluable’ service providers with phenomenal use and non use values.

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The report deals with estimation of evaporation losses from water surface in Tawa reservoir in Hoshangabad district of Madhya Pradesh. The study is third in the series of evaporation studies to assess the adaptability of different methods for estimation of evaporation from free water surfaces in semi-arid areas. The estimates of evaporation from free water surface obtained by four methods namely Penman, Kohler, Van Bavel and Morton are compared with observed pan values on monthly, seasonal and annual basis.

Analysis of surface runoff and baseflow at Tambarapani basin – A research report by National Institute of Hydrology
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The report presents the analysis of surface runoff and baseflow carried out for the Ariyanayakipuram anicut, Tambarapani basin, Tamil Nadu for a period of 13 years (1983-95). The hydrological behavior of catchments is a very complex phenomenon and is controlled by a large number of climatic and physiographic factors that vary in time and space. The analysis shows that the contribution of baseflow at Ariyanayakipuram anicut was observed to be more.

Estimation of infiltration rates in the Suddagedda basin of East Godavari, AP – A research report by National Institute of Hydrology
The report on Suddagedda basin, a representative basin of the east flowing rivers, presents the outcomes of the infiltration tests carried out using Double Ring Infiltrometer. Posted on 24 Jul, 2010 06:01 PM

The report on Suddagedda basin, a representative basin of the east flowing rivers of medium sized basins in the east coast of India, presents the outcomes of the infiltration tests carried out using Double Ring Infiltrometer. The basin soil is mainly grouped into three types viz clay loams to clay, sandy loams and forest & loamy skeletal. A total of twenty-eight infiltration tests have been conducted using double ring infiltrometers.

Daily rainfall-runoff modeling of Brahmani river at Rengali reservoir, Orissa – A research report by National Institute of Hydrology
The report presents a hydrologic simulation model, HYSIM for modelling the daily flows of the Brahmani river at Rengali reservoir in Orissa. Posted on 24 Jul, 2010 05:50 PM

The report presents a hydrologic simulation model, HYSIM for modeling the daily flows of the Brahmani river at Rengali reservoir in Orissa. Considering the large catchment area of 25,250 sqkm at Rengali reservoir, for modeling purposes the basin has been divided into two sub-basins viz, Upper Sub-basin and Lower Sub-basin. The Upper Sub-basin having a catchment area of 16,900 sqkm up to Bolani gauging site is treated as a nominal sub-basin since the daily flows from this sub-basin as recorded at Bolani gauging site are available.

Derivation of Geomorphological Instantaneous Unit Hydrographs for small catchments in hard rock regions - A research report by National Institute of Hydrology
In this study, Clark model parameters to geomorphological characteristics has been used to develop Geomorphological Instantaneous Unit Hydrographs for two hard rock catchments. Posted on 24 Jul, 2010 10:31 AM

In the study, the methodology developed at the National Institute of Hydrology to relate Clark model parameters to geomorphological characteristics has been used to develop unit hydrograph for two hard rock catchments, Barchi nala and Malaprabha up to Khanapur. This model has already been successfully implemented for simulation of flood events in small catchments of Upper Narmada and Kolar sub-basin of Narmada river as well as the Tapi sub-zone.

Proposing a National River Authority of India (NRAI)
In hope of a better river management Posted on 23 Jul, 2010 04:29 PM

Intervening at the urgency of the water situation of the country and need in larger interest of the people and nation from political, legal, social, administrative, commerce,trade,cultural, world tourism angles, apart from agricultural and drinking water angle; annual devastation by floods,and loss by drought. One single Authority, with P.M. as Chairman may hopefully bring expected and good results in river management; riverine rejuvenation - National River Authority of India

Here is a draft proposal for such an authority to be created.

We are looking for collaborations on making this a reality.

Please post your comments.

Watershed prioritization of Ukai dam catchment in Gujarat using remote sensing and GIS – A research report by National Institute of Hydrology
In the present study, watershed prioritization of the catchment immediately upstream of the Ukai reservoir has been carried out using the Watershed Response Model. Posted on 20 Jul, 2010 08:29 PM

In the present study, watershed prioritization of the catchment immediately upstream of the Ukai reservoir has been carried out using remote sensing technique. The Watershed Response Model (WRM) has been used for this purpose. This model utilizes the Normalized Difference Vegetation Index (NDVI) and the Soil Brightness Index (SBI), the two important parameters responsible for soil erosion.

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