Water resource developments

This page provides an overview of the potential benefits and adverse impacts of planned water resource developments.

Potential benefits

+ Hydropower makes up almost half of the growth potential of the four sectors (hydropower, fisheries, agriculture and navigation) combined.

+ Hydropower development can increase electricity security. Increased access to electricity from hydropower or other energy sources has the potential to improve the livelihoods of rural communities and reduce costs in the agricultural sector; e.g. for sprinklers and water pumps.*

+ Expansion of agricultural areas in combination with increasing irrigation capacity contributes to food security, increasing rice production and reducing production variability.

+ Increased flow of the Mekong River during the dry season due to discharges from hydropower may be beneficial for irrigated agriculture in certain river reaches and reduce sea water intrusion in the Mekong Delta.

+ River stretches with sufficient water depth created by hydropower dams improve navigation and reduce the need for dredging, allowing larger vessels to navigate year-round.

+ Development of navigation enhances the low-carbon waterway transport of cargo and passengers and may enhance river tourism.

+ Flood and drought issues may be better managed through responsible and joint operation of those hydropower dams that are able to store water during the wet season and assist in the management of flood peaks downstream.

+ Flood protection works in the areas at most risk can offset the predicted increase in future flood damage.

* Common knowledge, not specifically assessed in the Council Study.

Potential adverse impacts

The developments proposed are likely to reduce resilience and increase vulnerability of rural communities in the Mekong impact corridor, with the main benefits going to power companies and consumers mainly outside the corridor at the expense of fishing and rural households.

The connectivity related impacts of mainstream and tributary hydropower dams, such as trapping of sediment, disruption of fish migration paths and alteration of flow regimes, are substantial and far-reaching, and overshadow those of all other planned water resource developments in the LMB.

Trapping of bed and suspended sediment in tributary and mainstream dams of the Mekong Basin, including China, significantly increase river erosion in the LMB requiring significant expenditure on bank protection in Cambodia and Viet Nam’s Mekong Delta, and reduce the deposition of nutrient-rich sediment on floodplains with low soil fertility.

Reservoirs created by mainstream hydropower dams, the construction of bank and flood protection structures, and barriers to fish migration have wide-ranging ecosystem impacts, especially on Mekong fish species. However, deeper lake-like habitats are beneficial for others such as bivalves, frogs and snails.

Reduction in the wet season flood pulse limits the duration, depth and extent of inundation of floodplain habitats and therefore reduces productivity, particularly of the Xe Bang Fai floodplains in Lao PDR, the Cambodian flood plains, the Tonle Sap system and the Mekong Delta.

Agricultural expansion comes at the cost of losing forests and wetlands, accelerated soil erosion, increased use of agro-chemicals, land degradation and reductions in the stocks of natural capital, and associated flows of ecosystem services.

Navigation-related channel improvement activities, their maintenance, the construction of infrastructure such as ports and operational activities can potentially affect the environment and fisheries.

Rapid industrialization and urbanization tends to result in the pollution of water bodies adjacent to development areas, where untreated wastewater is discharged into natural water systems or leached into soils.