Comparative Assessment of Spatial Variability and Trends of Flows and Sediments under the Impact of Climate Change in the Upper Indus Basin

Abstract

Extensive research of the variability of flows under the impact of climate change has been conducted for the Upper Indus Basin (UIB). However, limited literature is available on the spatial distribution and trends of suspended sediment concentrations (SSC) in the sub-basins of UIB. This study covers the comparative assessment of flows and SSC trends measured at 13 stations in the UIB along with the variability of precipitation and temperatures possibly due to climate change for the past three decades. In the course of this period, the country’s largest reservoir, Tarbela, on the Indus River was depleted rapidly due to heavy sediment influx from the UIB. Sediment management of existing storage and future planned hydraulic structures (to tap 30,000 MW in the region) depends on the correct assessment of SSC, their variation patterns, and trends. In this study, the SSC trends are determined along with trends of discharges, precipitation, and temperatures using the non-parametric Mann–Kendall test and Sen’s slope estimator. The results reveal that the annual flows and SSC are in a balanced state for the Indus River at Besham Qila, whereas the SSC are significantly reduced ranging from 18.56%–28.20% per decade in the rivers of Gilgit at Alam Bridge, Indus at Kachura, and Brandu at Daggar. The SSC significantly increase ranging from 20.08%–40.72% per decade in the winter together with a significant increase of average air temperature. During summers, the SSC are decreased significantly ranging from 18.63%–27.79% per decade along with flows in the Hindukush and Western–Karakorum regions, which is partly due to the Karakorum climate anomaly, and in rainfall-dominated basins due to rainfall reduction. In Himalayan regions, the SSC are generally increased slightly during summers. These findings will be helpful for understanding the sediment trends associated with flow, precipitation, and temperature variations, and may be used for the operational management of current reservoirs and the design of several hydroelectric power plants that are planned for construction in the UIB.

Sustainable water resources development and management in large river basins: an introduction

“…The annual runoff of the Indus Basin is about 207 billion m 3 , originating mainly from the melt water of glaciers (Gascoin 2021 ). Global warming has accelerated the melting of Himalayan glaciers, raising the river runoff in a short period of time, but the amount of river water resources will be greatly reduced in the next few decades (Hussan et al 2020 ). Study has found that the rate of temperature rise in the upper Indus Basin is higher than that in the lower Indus Basin, and the river flow in the sub-basin is positively correlated with the average temperature and rainfall (Ashraf and Hanif-ur-Rehman 2019 ).…”

Spatiotemporal variations in runoff and runoff components in response to climate change in a glacierized subbasin of the Upper Indus Basin, Pakistan

“…There are two climatic fronts responsible for the precipitation in this region; the monsoon (which originates from the Bay of Bengal in summer) and the westerlies (which originates from the Caspian Sea and Mediterranean region during winters and springs). Most of the annual precipitation falls in winter and spring in the form of snow because of westerly disturbances (Hewitt, 2011;Ul Hussan et al, 2020).…”

Innovative polygon trend analysis of monthly precipitation (1952–2015) in the Hindukush‐Karakoram‐Himalaya river basins of Pakistan

“…Numerous studies have been conducted in the last two decades in the HKH region of Pakistan to evaluate the impacts of climate change on streamflow and the mass balance of glaciers (Immerzeel et al ., 2010; Tahir et al ., 2011; Ashfaq et al ., 2014; Palazzi et al ., 2015; Rahman and Shaw, 2015; Mahmood et al ., 2016; Greene and Robertson, 2017; Muhammad et al ., 2019; ul Hussan et al ., 2020; Ashraf et al ., 2021; Latif et al ., 2021). For example, Archer and Fowler (2004) analysed the seasonal and annual variation in precipitation during 1961–1999 and concluded that there was an increase in winter, summer, and annual precipitation.…”

“…Most researchers (Khattak et al ., 2011; Sharif et al ., 2013; ul Hussan et al ., 2020; Yaseen et al ., 2020) investigated the variations in temperature and precipitation in the Upper Indus Basin (UIB) with a different number of climatic stations and data durations utilizing conventional detection methods such as Spearman ratio and Mann–Kendall. All these tests consider assumptions such as serial independence of the given time series, prewhitening, normality of the data, and nonexistence of serial comparison among different sections of the same record (Şen, 2017a; 2017b; Sen et al ., 2019; Ceribasi and Ceyhunlu, 2020).…”