The upper Mekong and upper Salween basins
The Ganges basin
The Indus basins
Rainfall Rainfall projections in summer show an increasing trend over both upper basins, with an increase of about 5–10% over the southern areas where the normal precipitation is low. In the upper part of these basins where the normal precipitation is higher, the projected increase ranges from 10–25%. Rainfall projections in winter also show increasing trends of about 10% over most parts of the basins. However, a small area over the southern part of the central area of the basins shows a decreasing trend by up to 5%. Temperature Future warming in the summer season is projected over the entire upper Salween and Mekong basins, mostly in the range of 1.5–2.5°C, although it may exceed this in some pockets. RCP 8.5 shows a greater area with warming of between 2–3°C than RCP 4.5. Greater warming is projected in the winter than the summer, although the scenarios differ: RCP 4.5 results in projections of warming between 1.5–3°C, while RCP 8.5 results in projections of warming of 2–3°C or higher.
Rainfall In the summer, both scenarios project a 10–25% increase in rainfall over most of the basin, and exceeding 25% over the central north of the basin. RCP 8.5 results in projections with pockets of lower increase of up to 10% within the central and eastern parts of the basin. In the winter, both scenarios project a decrease in precipitation over the mountain range of up to 10%. RCP 8.5 shows a decrease extending south through the central and eastern parts of the basin. The rest of the basin will see an increase in precipitation ranging from 5–25%. During monsoon season rainfall is projected to increase by 15% and 14% for RCP 4.5 and RCP 8.5, respectively. Temperature Overall, the Ganges basin is projected to become warmer in the summer by about 2°C, with a higher increase projected in the north along the mountain range of up to 3°C. In winter, a projected increase of 2–3°C is widespread across the basin, and of up to 4°C along the mountain range. RCP 8.5 generally results in projections of higher temperature changes.
Rainfall Precipitation is projected to increase in summer over the northern, central-eastern and southern parts of the Indus basin, while over the central-western part of the basin it is projected to decrease. In the regions of highest rainfall along the mountain range, the increase is projected to be between 10–25%. Winter precipitation is also projected to decrease in the central-western part of the basin, as is summer precipitation. Whereas in the northern and southern parts of the basin, it is projected to increase between 5–10%. In terms of extreme rainfall events, a study by Rajbhandari et al. (2014) 105 suggests an overall increase in the number of rainy days over the northern part, and a decrease over the southern part of the basin. However, it also projects a decrease in the number of rainy days accompanied by an increase in rainfall intensity in the border area between the upper and lower basins, where the rainfall amount is highest. Temperature In summer, a major part of the basin is projected to warm by 2–3°C and up to 5°C under RCP 4.5 – and even more under RCP 8.5 in some pockets in the northern part of the basin. The southern part of the basin is projected to warm by a lesser amount, ranging from 1–2°C. Winter is projected to warm by 2–4°C across the basin in both scenarios, with very few areas either exceeding 4°C or lower than 2°C.
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