Predicting the effect of atmospheric pollution on soil and surface water acidification in the Middle Hills of Nepal

Rapid population growth and the expansion of South East Asian economies have lead to recent concerns regarding the effects of anthropogenic pollution on the environment. The RAINS-ASIA source-receptor, atmospheric transport model, is used to produce scenarios of future anthropogenic sulphur deposition. This is used as an input to the MAGIC model for prediction of future changes in the hydrochemistry of two catchments of the Likhu Khola watershed in the Middle Hills region of Nepal. Since much of this region is under intense cultivation and the application of mineral fertilisers may be contributing to soil and surface water acidification and loss of soil fertility, a best- and worse-case scenario for fertiliser application are incorporated to assess the overall anthropogenic influence upon soil and surface water acidification. The results indicate a decrease of soil base saturation and streamwater ANC, especially under the worst-case scenario of increased acidic deposition and increased fertiliser use. However, the pH status of soils and surface water are predicted to decrease only marginally as a result of the abundant supply of base cations from the highly weathered bedrock and deep soil. The problem of increased acidification of soils and water at a regional scale, however, should be addressed.