Flooding and hydropower: missed opportunities in the Koshi Basin?

Source(s): Water Science Policy
  • The Koshi River is one of the largest river systems in South Asia and has a lot of potential for development
  • Development activities in a river system often take place with a very narrow-minded perspective, undermining the impacts that occur downstream
  • ">">
  • Massive flooding in the downstream area could be avoided if adequate and appropriate water-based infrastructure is implemented upstream as this can barricade the water for a period of time
  • ">">

By Pratik Poudel

The Koshi Basin supports many livelihoods in the South Asian region. The areas surrounding the Koshi River (found within the Koshi Basin) are home to nearly 10 million people upstream and more than 30 million people downstream, covering many parts of Nepal, India and a small proportion of China. The water resource of the Koshi region is largely untapped. For instance, a study showed that there is potential to build eleven hydropower and water storage projects in the region. 29,733 GWh of hydropower could be generated annually and 8382 million m3 of water could be stored.  However, the region is constantly faced with a lot of difficulties. The people living along the Koshi River live in one of the most impoverished and overcrowded regions in the world.  40% of the population of the Nepalese part of the Koshi Basin live below the poverty line, with the national average being 25%.

Why are upstream-downstream linkages in a river system important?

In order to effectively manage a river system, it is important to understand the complex upstream-downstream interlinkages. A glacier-fed river like Koshi, which flows from mountainous areas of Tibet to the downstream plains of Nepal and India and finally joins the Ganga in the Kursela region of India, connects upstream and downstream areas across extensive spatial scales. Along its journey, the river meanders not only through gorges and valleys but also across sharp changes in social and legislative territories. The problems and complexities that take place in the upstream areas such as Glacial Lake Outburst Flood (GLOF), spring depletion, and deforestation, naturally affect the flow of the river and its surrounding communities downstream.

Understanding upstream-downstream linkages in hydrological processes is essential for water resource planning in river basins. It is particularly critical in basins that combine extreme changes in both climatic and geological conditions and different legislations. The Himalayan region is a clear example of this. Upstream, many river basins that emerge from the Himalayan plains are very sparsely inhabited, poorly accessible and widely glaciated with fragile ecology. Downstream, major rivers like the Ganges are the cultural centre of entire civilizations and home to one fifth of the world’s population

Why is Koshi so important?

The Koshi River is one of the most at-risk rivers in South Asia. For example, out of the 38 districts in Bihar, 28 are flood prone. The area experienced major floods in 2007, 2008, 2011, 2013, 2016 and 2017, causing severe loss of life and property, including damage to crops, roads and other vital infrastructure. To some extent, the occurrence of floods is connected to the dynamics of upstream-downstream linkages, demonstrating that their management therefore requires joint actions at various levels of governance.  

There is limited research available with regards to the upstream-downstream linkages in the Koshi Basin. During a consultation program organized by ICIMOD in the Bihar region of India, almost all of the participants agreed on a basin-wide approach to reduce flood-related disasters in the region, which includes challenges associated with upstream-downstream linkages, erosion and sedimentation, and climate change. This emphasizes the significance of linking upstream activities with downstream impacts as those most affected are already calling for this sort of holistic governance, even with incomplete information.

Additionally, vulnerability from these hazards varies according to where one finds themselves in the basin. A study found that populations in mountainous regions are the most vulnerable, followed by mid-hill and Terai regions. Each area also faces its own type of vulnerability. For example, the mountain and mid-hill regions are more stressed in terms of resource strains and ecological security, while plain areas suffer from human development pressures. While each area has its own challenges, these are all interconnected through upstream-downstream linkages, and pressures in one region may eventually lead to the generation of different types of pressures in other regions. 

The potential of hydropower and the role of upstream-downstream linkages

The Koshi Basin has a hydropower potential of 23,000 MW, out of which 10,000 MW is economically viable. In 1985, the Japan International Cooperation Agency (JICA) identified 11 potential hydroprojects (seven run-of-the-river and four storage types) along different tributaries, and various surveys have suggested that more than 6,000 MW of hydropower could be generated. However, current hydropower generation is less than 200 MW. Out of the proposed projects in the Koshi Basin, JICA gave high importance to the Saptakoshi High Dam Project, which has a storage potential of 8500 million cubic meters (MCM). Similarly, the proposed large reservoir in Chatara could supply year-round irrigation in the downstream areas. A proposed barrage in the Nepalese Saptakoshi region at about 8 km below the dam would regulate water for irrigation and navigation. This water storage in Saptakoshi could store more than one-fourth of the total annual water flow. Monsoon flow constitutes 70.8% of the total flow and provides around 34 km3 of water storage, which means that almost 40% of the monsoon water could be stored (dependent on whether the reservoir is emptied before the onset of the monsoon), which would have significant impacts on flood moderation downstream. Similarly, development of a 165 km navigation canal from Chatara to Kursela would link Nepal to India’s National Waterway 1 along the Ganges, consequently lowering both countries’ import and export prices through the use of water as transport. 

During the Jure Landslide in 2014, caused by erratic rainfall in the Sunkoshi river, various infrastructures along the river, such as roads and hydropower projects, were damaged and around 150 people lost their lives. The losses due to flashfloods in the downstream area had the potential to be huge. However, this  was minimized when the excess water was inundated in time from the Sunkoshi dam. Therefore, as a result of upstream-downstream linkages the flood’s potential losses were minimized. Water-related infrastructure can help to intensify upstream-downstream linkages, both in terms of blocking water flow during intense flooding in the upstream regions or sending stored water for irrigation in the downstream areas during dry seasons. In a developing context such as the Koshi Basin, structures like dams and reservoirs can store water during flood periods, which can be available during dry seasons and provide necessary water for irrigation,  power supply and also aid inland navigation. While considerations around (downstream) environmental impacts of hydropower must inform any project, the benefits to the impoverished and flood-prone population along the banks of the Koshi river seemingly greatly outweigh the costs. Integrated and equitable transboundary upstream-downstream investment and management of such hydropower projects has the potential to benefit millions.

Please note: Content is displayed as last posted by a PreventionWeb community member or editor. The views expressed therein are not necessarily those of UNDRR, PreventionWeb, or its sponsors. See our terms of use