The Ganges Water Diversion: Environmental Effects and Implications

Water is the most powerful agent in shaping the earth’s surface through the processes of rivers, glaciers, ground water, weathering, mass movement, and oceans. Water is also an important element that played a pivotal role in the development of the world’s civilizations. Since the dawn of civilization, humans have harnessed water in many different ways for their physical existence and the sustenance of the environment. They have devised ways of capturing, storing, purifying, and diverting freshwater resources to reduce their vulnerability to highly variable river flows and precipitation. Early agricultural civilizations developed in regions where precipitation and river flows were abundant and could be easily and reliably harnessed. Humans extended their river water-based transportation systems to sea travel and trade. With the growing need of goods, commodities and a safer environment, humans altered the natural hydrological cycle through massive engineering projects for water diversion, flood control, urban and rural water supply, hydropower, navigation and irrigation. The development of water resources served human societies in many positive ways as well as generated adverse effects. This book presents an analytical account of the effects caused by water diversions by major engineering works such as barrages1 and other structures built on the Ganges River (Figure 1.1) in South Asia.

The Ganges is an international river shared by China, Nepal, India and Bangladesh. With regard to the distribution of the 109.5 million hectares (ha) basin area, India shares 79%, Nepal 14%, Bangladesh 4% (this is equivalent to 32% of Bangladesh) and China 3%, respectively (Table 2.1). The river has great importance for the socio-economy of the co-basin countries. It is estimated that about 451 million people (based on 2001 census reports of China, Nepal, India and Bangladesh) are directly or indirectly dependent on the Ganges River.

The Farakka barrage (Figure 3.1 and Box 3.1) was constructed in 1971 across the mighty river Ganga (Ganges) to divert part of the main river flow from Ganga to its tributary, the Hooghly (Figure 3.1). With gradual silting of the Hooghly off-take near Jangipur in the Murshidabad District of West Bengal, upland discharge to the Hooghly was being reduced drastically (Mookerjea, 1974). The problems of the Hooghly are high salinity, heavy siltation, poor navigability and the increasing frequency and intensity of tidal bores (Abbas A.T., 1984). Depth of the Hooghly was reduced due to the deposition of sediments carried by the high tides from the Bay of Bengal. Accelerated sedimentation, usually observed in the zone of saline and freshwater interface, has very high spatial and temporal variation. Annual dredging costs increased to Rs. 315 million (unadjusted) in 2001 from Rs. 75 million in 1973 to permit the navigability of the river where the port of Kolkata is situated (The Hindu, 2001). Model studies at Central Water and Power Research Station (CW and PRS), Pune, as well as at River Research Institute, West Bengal, were carried out to determine the amount of Ganga flow that must be diverted to the Hooghly for flushing out the sediments and restoring its navigability. From these model studies as well as some analytical studies conducted by the hydraulic experts Dr. Hansen from Germany and Engineer Joglekar from India, it was finally decided to divert 1,134 m³/sec (40,000 ft³/sec) of flow. Accordingly, the Farakka Barrage and the feeder canal linking the Ganga with the Hooghly River were constructed at an approximate cost of Rs. 2,000 million (1971 price).

Channel morphology adjusts in the different time-scale — long, medium and short — to changing water and sediment discharges (Richards, 1982). Long-term influences — climate, hydrologic and gradual tectonics — cause gradual, progressive adjustment of the alluvial channels. Medium-term adjustments are often caused by human activities. Natural hazards like earthquakes and volcanic eruptions are also responsible for medium-term adjustment. Several studies have assessed the medium-term adjustment due to human activities and natural hazards (Kondolf et al., 2002; Yang et al., 2002; Goswami et al., 1999; Simon, 1989; Burnett and Schumm, 1983; Galay, 1983). In these cases, the change in sediment transport is the triggering agent. On the other hand, short-term channel adjustment is caused by individual extreme events, like a catastrophic flood.

The diversion of Ganges water in India by the Farakka Barrage and other engineering structures has resulted significant changes in the hydrology of the Ganges River system in Bangladesh. The system is comprised of the main Ganges River; the Mahananda, an important tributary; and the Mathabanga and Gorai, two distributaries. The analysis of discharge data of the Ganges and Gorai Rivers discussed in Chapter 2 demonstrate a significant reduction of water supply in the dry season and a considerable increase in the monsoon. Reduction in dry season discharge in the Ganges system in Bangladesh has generated a series of hydro-environmental implications.

River Ganga (Ganges), the most important river system in India and one of the largest (2,525 km) in the world, drains about one fourth area of the country. It has an annual runoff of about 493 km³ and carries 616 × 10⁶ tonnes of suspended solids to the Hooghly Estuary (Qasim et al., 1988). River Ganga is considered as the second major river of the world in terms of suspended load and is the main contributor of sediments to the Bengal fan, which is the largest deep sea fan in the world (Lisitzin, 1972).

Rivers and streams with their associated flood basins and upland areas form complexly linked ecosystems in which land, water, plants, animals and humans interact and evolve in response to the interactions of the components of the system. Thus changes in any component of the system will impact the physical, chemical, and biological process occurring within the river system. River systems normally function within the natural ranges of flow, sediment movement, temperature and other variables, in what is termed “dynamic equilibrium.” When changes in these variables go beyond their natural ranges, dynamic equilibrium may be lost, often resulting in adjustments that are detrimental to the integrity of the ecosystem, which includes ecosystem structure, ecological process, regional and historical context, and sustainable cultural practices.

The Ganges basin in Bangladesh has a humid climate, but it is vulnerable to drought in the summer as well as during the monsoon months. Mean annual rainfall ranges from 1,270 mm in the Western part of Raj shahi to about 3,000 mm in the coastal region in the South, meaning that the climate of the Western Ganges basin is naturally unfavorable for agriculture. Agricultural activities are largely dependent on the water supply from the Ganges River and its distributaries. The Ganges-Kobadak (G-K) project (Figure 9.1 and Box 9.1), one of the country’s largest surface water irrigation projects based on the water supply from the Ganges River was planned in the 1950s.

Planned measures on shared rivers and lakes have long been a source of enormous tension between riparian states.¹ The environmental dimensions of such measures are also recognized in comparatively recent reports and documents. The World Commission on Dams, in its Report of 2000, observed that large dams and diversion projects can lead to the loss of forests and wildlife habitat, aquatic biodiversity, and can affect downstream flood plains, wetlands, riverine, estuarine, and adjacent marine ecosystem.² The Commission therefore underscored the necessity of “identifying the legitimate claims and entitlement” involved in such projects.³

The environmental impacts caused by the water diversion at Farakka Barrage are significant. In the last five decades it has generated a lot of debates among politicians, bureaucrats, academics and has affected dwellers of lower catchment areas of the Ganges River. The Farakka Barrage was built primarily to serve the twin purpose of regulating the amount of Ganges (Ganga) water to flow out from the Indian territory into Bangladesh (erstwhile East Pakistan); and to ensure that sufficient water (as much as 1,134 m³/sec or 40,000 ft³/sec) could be diverted to the Bhagirathi-Hooghly River through a feeder canal to enable regular flushing of silts at Kolkata Port. This arrangement has tangled the Farakka Barrage often in controversy as India and Bangladesh have been disagreeing over the sharing of the Ganges water between the two countries. In the recent past, some efforts have been made to resolve this contentious dispute between the two nations, including the signing of a 30-year Ganges Water Treaty (see Annex I), but no serious thoughts have been granted or furnished to reach a meaningful and lasting solution to the problem.

Diversion of water from the Ganges River through major engineering structures has caused significant environmental effects in the downstream and upstream parts of the basin. In Bangladesh, major impacts are observed in: water supply, river morphology and regulation, navigation, salinity, forestry and ecosystems, agriculture and land degradation and fishery. However, areas (upstream and downstream) adjacent to the Farakka Barrage are also impacted by the increased flood hazards, reduction in fisheries and erosion. Water diversion through the Farakka Feeder Canal to the Bhagirathi-Hooghly River (Figure 12.1) positively benefited Kolkata Port by increasing draft for vessels. Water supply to the Kolkata City has also improved. Table 12.1 summarizes the impacts of diversion on various sectors in the upstream and downstream areas of the Ganges River.

Sharing of the Ganges water was a subject of bilateral dispute between Bangladesh and India for more than three decades. Before the emergence of Bangladesh in 1971 as an independent nation, Pakistan and India wrangled over it for 20 years. The sharing problem seriously arose in 1974 when India had completed a barrage on the Ganges River at Farakka (18 km from the West border of Bangladesh) to divert 1,134 m³/sec of water to the Hooghly-Bhagirathi River, in order to make the port of Kolkata navigable by flushing down the silt that deposited over the centuries in the riverbed (Figure 13.1) (for details see Chapter 1). It was discussed at a meeting Head of the States of India and Bangladesh in 1974 (Abbas A.T., 1982).

Equitable sharing of common resources among all co-sharers is now a well-established principle. In the context of water resources, for example, clear and forceful codification of this principle is available in the Helsinki Rules (ILA, 1992) and the 30-year Ganges [Water-Sharing] Treaty between Bangladesh and India signed in December of 1996. Also, common resources are usually best developed and utilized for maximum possible mutual benefit under the cooperative arrangement among the co-sharers. Several studies (e.g. Ahmad et al., 1994; Adhikary et al., 2000; and Ahmad et al., 2001) have shown that the benefits derivable-in terms of, for example, irrigation, hydropower generation, flood mitigation, and freshwater supply to stem salinity ingress — from water resources development and utilization in the Ganges-Brahmaputra-Meghna (GBM) basins will be much larger, on a win-win basis for all, under a cooperative regime involving all co-riparians, compared to what may be possible under separate national approaches, pursued by the countries sharing the basins: Bangladesh, India, Nepal, and China (Tibet). This study focuses on Bangladesh, India and Nepal, through which the Ganges River systems mostly flow, having originated in China (Tibet).