Acidification of Surface Water and Its Prediction in Japan

A Japanese nationwide survey was conducted by the Central Reseatch 1nstihte of the Electric Power Indushy (CRIEPI) on stream water quality and soil chemistry in 253 mountainous watersheds in 1991. The result suggests that most of the watersheds have sufficient acid neutralization capacity (ANC) except a few ones with low ANC. These watersheds vulnerable to acid deposition need further reseatth and monitoring in more detail. For the prediction of stream water quality, the Integrated Lake and Watershed Acidification Study (ILWAS) model developed in the United States was well applied to a Japanese watershed in the hydrological and water quality simulations during one year. However, it was found that the estimation of chemical weathaing in the watershed is crusial to the reliability of long-term prediction using the ILWAS model. Therefore, future research is needed for better estimation of chemical weathering in watershed.