This e-book collates information on watersheds and watershed management in the South Asia Region (SAR) in order to guide the planning and prioritization work of World Bank teams, clients, and development partners in the region. Watersheds are an appropriate and effective unit for managing ecological assets given the interconnected nature of activities and management impacts within a watershed both locally and regionally as well as upstream and downstream. In the SAR as elsewhere, watershed management practices in upstream countries can impact social, economic and environmental conditions in downstream countries within these watersheds. For example, land management practices within a watershed (e.g., deforestation and forest degradation; road and other infrastructure construction) can increase sediment load at downstream hydropower facilities. Road construction practices can also contribute to landslides, further increasing sediment load in waterways. The unsustainable overuse of water supply for consumption and irrigation and dam construction and use in upstream countries may impact the quantity and quality of water available in downstream countries. Overall, upstream land degradation and deforestation and large-scale water development schemes mid- and downstream can and have adversely impacted downstream watershed communities in South Asia.
Watersheds provide a variety of ecosystem services and economic benefits that can be leveraged through sustainable watershed management.Evidence has shown that managing a watershed sustainably can generate multiple benefits, including socio-economic and ecological gains. Sustainable watershed management maintains critical ecosystem services including improving water quality through filtering pollutants, nutrient cycling, and sediment retention; flood control and increased resilience to the impacts of climate change; habitat provision for biodiversity; carbon sequestration and storage; and the provision of critical goods such as food or timber. Other economic benefits afforded by watersheds include reduced costs for providing drinking water, maintaining infrastructure; flood prevention and damage recovery; and hydropower production. Well managed watersheds can also offer health benefits, such as lower rates of illness where water is cleaner as a result of the filtering service of the watershed.
Investing in the maintenance of healthy watersheds has many economic benefits. Many ecosystem services such as carbon storage, nutrient cycling, water filtration and storage, air filtration, and soil formation are often under-valued when making land use decisions. Assigning monetary value to these ecosystem services is essential for encouraging conservation and its associated economic benefits for the local communities. Maintaining riparian connectivity and natural processes in the landscape ensure sustainable and cost-effective provision of clean water over time. Investing in the maintenance of healthy watersheds can significantly lower costs associated with water treatment and flooding.
Managing sediment in South Asia, particularly in the mountainous Himalaya, is a critical aspect of watershed management in the region. Erosion and sedimentation result from deforestation, agricultural practices that leave soil exposed after harvest, and road and building construction. Excessive erosion and sedimentation have detrimental impacts on livelihoods and infrastructure through reducing agricultural yields, hydropower capacity, water quality, resilience of roads, and triggering landslides. The ramifications of these impacts in SAR and in other areas highly prone to erosion and sedimentation are enormous.
Nature-based solutions (NBS) can reduce erosion and sedimentation, with multiple cross-sectoral benefits. Managing erosion and sediment through NBS such as afforestation, soil and water conservation measures, and improved agricultural practices can reduce risks and economic losses to costly infrastructure while also improving livelihoods and resilience in the landscape. Importantly, disruptive technologies, evolving at an accelerated pace, promise to bring new opportunities for better decision-making by generating and analyzing larger quantities of data; new ways of producing things or operating systems; and new platforms through which stakeholders can engage and share knowledge.