This paper establishes a comprehensive assessment model to measure the regional impact of climate change on Taiwan¡¦s water resources. Working from future rainfall data simulated by Japan¡¦s high-resolution GCM model JMA/MRI TL959L60 in a SRES-A1B scenario, we first apply climate change to an assessment model of renewable water resources to estimate the volume of renewable water resources on a regional basis. We then conduct a water resources system simulation based on estimates of future water needs, regional reservoir effective capacity and renewable water resource volume. This paper uses three water resource assessment indicators: the annual water utilization ratio indicator, the water shortage indicator and the extreme event occurrence indicator. Through fuzzy comprehensive assessment, we divide the evaluation set into five levels: very good (L1), good (L2), fair (L3), poor (L4) and very poor (L5). Results indicate that, given the effects of future climate change (2080 - 2099) and the increase in water demand, future water resources conditions in northern and eastern Taiwan will not be significantly different from historical levels (1979 - 1998) and will maintain a ¡§good¡¨ level (L2), while the conditions in southern Taiwan will visibly deteriorate from its historical ¡§fair¡¨ level (L3) to ¡§poor¡¨ (L4); and the future conditions for central Taiwan will be ¡§poor¡¨ (L4). The initiation of adaptation options for water management in southern and central Taiwan would be needed by increasing reservoir capacity and reducing overall water use.