The AWCI countries represent a wide variety of geographical, climatic and hydrological conditions and thus various tools and methods are required for climate change impact assessment. This article introduces some of the tools developed as a part of the AWCI activities. A hydrological model for cold regions was developed by incorporating a multi-layer energy-balance based snowmelt scheme into the Water and Energy Budget Distributed Hydrological Model (WEB-DHM). A method was developed for estimating snow depth spatial distribution in mountain areas using a radiative transfer model and microwave radiometer observations (AMSR-E satellite data) and validated in the Puna Tsang basin in Bhutan. Moreover, an improved statistical method for GCM precipitation output bias correction was developed that covers extreme rainfall, normal rainfall and frequency of dry days, and was validated in the Pampanga basin in the Philippines. In addition, the bias correction method and WEB-DHM model were employed in a climate change impact assessment study in the Philippines, focusing on flood peaks and droughts. Results showed future flooding trends are virtually certain to increase while drought trends are likely not to increase in the uplands but very likely to increase in the flood plains.