ABSTRACT
The image of irrigation often conflicts with that of the Mekong River Basin – a monsoonal region with a wet climate and periodic floods. In the countries of the Lower Mekong Basin (LMB), however, the wet season that runs roughly from June to October is, in many places, followed by a dry season for the rest of the year. The rain-fed uplands in Laos and Cambodia receive the most rainfall (3000mm) and the Korat Plateau in northeast Thailand receives the least, between 1000mm and 1600mm (MRC, 2003a). In the LMB countries, irrigation is a key means of securing monsoon crops – shifting from a single crop (mainly rain-fed wet season rice) to multiple cropping systems – and increasing crop yields. It is estimated that water abstraction for agriculture accounts for around 90 per cent of all water diversions (Cambodia: 94 per cent; Laos: 82 per cent; Vietnam: 86 per cent; and Thailand: 91 per cent) in the region (MRC, 2003a). Thailand and Vietnam have extensively developed their irrigation infrastructure; while investments have declined in the last few years, hydropower development is going rapidly ahead (especially in Vietnam and Laos; see Chapter 2 in this volume). Laos, because of its sparse population, and Cambodia, due to the recent history of war and political turmoil, still have a low degree of infrastructure development; but more investments are expected in the coming years.
