Abstract
The present study explored the changes in monthly streamflow in the Hindukush–Karakoram–Himalaya (HKH) region within Pakistan using the recently developed trend analysis method known as innovative polygon trend analysis (IPTA). The monthly streamflow data of 34 gauging stations installed in the HKH region was analyzed, and the Pettitt test was applied to check the homogeneity of the time series. The entire study area was divided into 13 sub-basins, and then changes in monthly streamflow of each sub-basin were explored using the IPTA method. The streamflow of high elevated glaciated and snow/ice-covered sub-basins (e.g., Shyok, Astore, and Chitral) have increased in high flow months (June–August), where there is a downward trend for the Hunza sub-basin in these months. In the Gilgit sub-basin, a transition occurred from no trend in May to a decreasing trend from June to August. The upstream gauges of Swat and Kabul sub-basins showed an increasing trend throughout the year, while downstream gauging stations in the same sub-basins exhibited a strong decreasing trend only in high flow months (June–August). The upper reaches of the Indus part in the Upper Indus Basin (UIB) showed increasing trends in high flow months (June–August), however the downstream gauges of UIB showed decreasing trends throughout the year. Overall, only the glaciated and snow/ice-covered sub-basins experienced increasing trends, while most other sub-basins faced decreasing trends in high flow months and increasing trends in low flow months (October–March). The enhancement of the seasonal pattern of streamflow in the upper reaches of UIB is possibly due to the melting of snow and ice that potentially influence floods and hydropower generation. The results of this study can result in a better understanding of the hydrology of the HKH region and support sustainable water management.
Highlights
The Indus System of Rivers (ISR) consists of three western rivers (Indus, Jhelum, and Chenab) and three eastern rivers (Ravi, Sutlej, and Bias)
The variations and changes in monthly streamflow in the sub-basins of the HKH region within Pakistan were analyzed using the recently developed trend analysis method known as the Innovative Polygon Trend Analysis (IPTA) method (Sen et al 2019)
Ul Hussan et al (2020) and Sharif et al (2013) reported that the streamflow increased for glacier and snow-fed sub-basins in the HKH region of Pakistan during December-June, whereas in our study, there is an increasing trend for all months in the glacial and snow-fed sub-basins Shyok and Astore of HKH. This contradiction is due to differences in the design of classical Mann Kendall trend test used in these studies and the recent assumptions free IPTA trend analysis method used in this study
Summary
The Indus System of Rivers (ISR) consists of three western rivers (Indus, Jhelum, and Chenab) and three eastern rivers (Ravi, Sutlej, and Bias). The five rivers (Jhelum, Chenab, Ravi, Sutlej, and Bias) join the Indus River at Panjnad Barrage, located in Punjab, Pakistan. The western rivers are fed by snow and ice melt runoff from the HKH region. Immerzeel et al (2010) stated that more than 50% of the Indus river water is contributed by glacier and snowmelt runoff from HKH, whereas the contribution of summer precipitation is relatively small (Immerzeel et al 2009). The Upper Indus Basin (UIB) is the Indus basin upstream of Tarbela and Mangla reservoirs, and these reservoirs are the primary source of irrigation and hydropower generation for Pakistan (Nie et al 2021; Rashid et al 2018). The changes in air temperature and humidity speed up the ablation of glaciers in this region (Harpold and Brooks 2018; Immerzeel et al 2010)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
