Introduction Climate change analysis indicates that one of the most notable impacts will be felt through modification of the hydrological cycle. Impacts on both natural and human systems will be particularly severe in developing countries, areas where a large number of inhabitants (many of whom are already marginalized) are those with primary-resource-dependent livelihoods. While levels of vulnerability to climate change determine the adaptation options available to individuals and communities, the ability of individuals and communities to act collectively deter­ mines their resilience and hence capacity to adapt to a changing climate (Kes­ kinen et al. 2009). In this sense, individuals and communities have interdependent relationships “with each other, with the institutions in which they reside, and with the resource base on which they depend” (Adger 2003: 388). In such interdependent relationships, vulnerabilities are often created by the under­ lying distribution of power, which determines the fairness of the rules upon which resource­ managing institutions base their decisions (Adger et al. 2005). Critical elements of vulnerability analysis – in effect, analyzing the extent of human security – therefore include how inequality and differential political and economic power increase the vulnerability of poor and marginalized groups (McLaughlin and Dietz 2008) and are shaped by social, economic and political trends and characteristics (Adger et al. 2005). The Lower Mekong Basin (LMB) is a case in point. It is home to approxi­ mately 65.7 million people (Sukhsri 2009) who reside within areas of four ripar­ ian countries: Lao PDR, Thailand, Cambodia and Vietnam and rely largely on subsistence agriculture based on rice and fish. Covering 77 percent of the overall Mekong River Basin (MRB), the LMB is regarded as the most important part of the MRB, environmentally and economically (Aerts and Droogers 2004). While the Mekong River provides the MRB with abundant water resources, the monsoon rainfall pattern dictates the wide variability in water availability within it. The livelihoods of those living off the floodplain ecosystem, where productiv­ ity is sustained by the flood pulse generated by annual monsoon floods together with the mainstream water level, are thus dependent on variations in climatic conditions.