Although Ireland is relatively well endowed with water resources, regional shortages can occur at certain times of the year, especially in the east and south east of the country. The rapid expansion of urban areas such as Dublin, Cork, and Limerick, associated with recent economic conditions, is putting an increasing strain on the water supply infrastructure. The increased demand for water comes mainly from the industrial and domestic sectors, with domestic demand increasing both as a result of population growth and rising water consumption per capita. As a result, low flows are becoming more frequent in some areas and it is likely that future climate change scenarios will exacerbate these effects. At the same time, many Irish rivers are prone to flooding, especially those in the west, with the Shannon being a prime example. Increases in winter precipitation over the western part of the island are likely to increase the magnitude and frequency of flood events, and increase the duration of seasonal flooding. The aim of this research, therefore, is to simulate patterns of runoff under baseline and future climate scenarios, at a fine spatial resolution, in order to assess annual and seasonal changes.