More than 160,000 miles of rivers across the world have lost their free-flowing status and over 260,000 km of rivers, including the Amazon, Congo, Irrawaddy, and Salween mainstream rivers, would lose their free-flowing status if new hydropower dams were built, according to a new study.
The study published in Global Sustainability says only about one-third of rivers that comes to less than 1000 km remain free flowing. The study says that the total stretch of free-flowing rivers at risk is longer than six times the distance around the Earth.
The study also states that dams and associated reservoirs have historically been a cornerstone of economic development in numerous countries. They provide several benefits like water supply for human populations and agriculture, flood risk reduction and hydro power production. However, the study shows that dams also fragment rivers, inundate habitat, disrupt sediment and nutrient transport, alter flow regimes, and block migration and dispersal routes for numerous species and can be a source of social and geopolitical conflict.
The researchers say that alterations of water and sediment flows can affect the shape of riverbeds, which can in turn trigger increased vulnerability to floods and droughts, especially in densely populated large tropical deltas.
The study maintains that reconciling dams with freshwater system health remains one of the world’s greatest conservation challenges and is fundamental to the maintenance and recovery of freshwater biodiversity and vital ecosystem services.
Solution
- A better balance between economic development goals and sustaining healthy rivers and the communities that depend on them can be achieved through expansion of existing policy and finance mechanisms at national, regional and basin scales.
- Numerous types of protection mechanisms for high-conservation Value Rivers exist around the world – from inclusion of rivers within national parks to designated Ramsar sites, water resource protection areas or water reserves.
- Wherever they are designated as protected, dam construction should be avoided
- Avoid fragmenting the water bodies by instating formal protections of rivers or by exploring alternative development options, such as non-hydro power renewable energy, like solar and wind. Early, system-wide planning is the best solution to meet development needs and keeps rivers and the benefits that they provide connected and flowing.
- Restoring rivers through dam removal, an increasingly popular option in the U.S. due to the high costs of dam maintenance and the negative impacts on surrounding ecosystems.
- Offsetting the negative impacts of dams. If one river is severed by a dam, there may be options to protect another river to ensure that similar values are maintained in the region.
