INTRODUCTION

Water supply is usually taken for granted in the humid tropics and perceived as stable, i.e. it is assumed that water availability will not change over a relatively long period. It is also often believed that water is an unlimited resource, hence water-related policies (if any) are seldom reviewed and adjusted. In reality water resources in the humid tropics are getting more and more depleted in terms of both quantity and quality (Bruijnzeel, 1990, 1998). The economic losses due to water shortage or excess result mainly from a lack of adjustment and responses in the public policy-making process regarding the use of resources. Water scarcity in particular and, hence, insecurity is a growing issue in areas where population pressure and rates of environmental degradation are high. Moreover, water scarcity is increasingly causing political and social tensions between upland and lowland communities and between neighbouring districts or countries or other political and administrative boundaries. Conflicts between the riparian states in the Lower Mekong Basin and within the Greater Mekong Subregion are classic examples. Controversy over the impacts of navigation and hydroelectric power projects is widespread through the region because three-quarters of the population of the Lower Mekong Basin, mainly farmers and fishermen, earn their living by utilising natural resources directly. Therefore an integrated management plan that involves the various stakeholders is necessary to avoid conflicts (Dubash et al., 2001).