Flood Inundation and Streamflow Changes in the Kabul River Basin under Climate Change

Abstract

The Kabul basin yields around 16% of the total annual water availability in Pakistan. Changing climate will alter the precipitation regime in terms of intensity and frequency, which will affect the water yield and cause flood hazards. Against this background, this study aims to quantify the impacts of changing climate on the water yield, its timings, and, more importantly, the associated flood hazards in the transboundary Kabul basin. For this, we used a rainfall-runoff inundation (RRI) model coupled with the snow and glacier melt routines and drove it for historical and future climates simulated by the atmosphere-only general circulation model (AGCM) at 20 km spatial resolution. The model simulations reveal that rainfall runoff contributes around 50% of the annual flows, and the rest is contributed by glaciers and snow melts. Annual precipitation is projected to increase by 14% from 535 mm, whereas temperatures will rise by 4.7 °C. In turn, the Kabul River flows will only increase by 4% to 1158 m3s−1 from 1117 m3s−1, mainly due to an increase in winter flows. In contrast to a minute increase in the mean river flows, the maximum flood inundation area is projected to increase by 37%, whereas its depth will rise between 5 and 20 cm.

Assessment of Water Resources under Climate Change in Western Hindukush Region: A Case Study of the Upper Kabul River Basin

“…Additionally, compared to the baseline period, there will be an increase in the seasonal streamflow during the rainy season and decreases in the dry season. The studies [42,51,52] also suggest that summer flows will continue to drop in the future, whereas spring and winter flows will increase in the Indus River Basin. The seasonal variation in streamflow can lead to more frequent floods during the wet season and droughts during the dry season due to less runoff and a higher ET in the UKRB.…”

“…It is quite clear that the water regime of the Indus River will have a decisive influence on the tributaries, including the Kabul River, in the future. Sohaib et al [42] found future seasonal shifts in the streamflow and the rainfall shifts at the Nowshera and Chitral watershed of KRB, and Ref. [18] found that the peak hydrograph split into two peaks; one formed in Mar-Apr indicated earlier snowmelt, and the second one in August, which was due to Monsoon rains increased in the Alingar watershed of the KRB.…”

“…The increment of annual surface runoff in the UKRB is due to an increase in the annual precipitation [43], and there are other factors that might offset this increase, for instance, a decrease in percolation and groundwater. Other factors, such as changes in temperature, could also potentially impact the hydrological cycle and contribute to changes in streamflow patterns [42]. Additionally, there will be a decrease in annual percolation and groundwater recharge, which could further reduce the water availability in the summer season.…”