25. Water resources. Altered precipitation patterns will lead to less reliable and reduced river flows during dry periods. Further pressure on the water supply will come from the projected increases in evaporation from paddy fields that are brought on by climate change. The agriculture, industry, and energy sectors will be negatively impacted at times of reduced water availability, and they will be forced to compete for limited water supplies. In 2020, water use is expected to increase to 120 billion m3 from 2008 consumption of about 80 billion m3 (ADB 2009). Upstream–downstream water management issues will become acute with climate change. For example, the development of upstream hydropower
can affect flow and sediment deposition patterns for downstream irrigation and agriculture, especially in the Mekong and Red river deltas. There are increasing but poorly understood effects on agricultural productivity due to constraints on water access for irrigation during the dry season and reduced sediment deposition on agricultural lands from irrigation and floodwaters.