Characterization of interannual and seasonal variability of hydro-climatic trends in the Upper Indus Basin

Muhammad Usman Liaqat,Giovanna Grossi,Shabeh Ul Hasson,Roberto Ranzi

doi:10.1007/s00704-021-03850-3

Abstract

High-resolution seasonal and annual precipitation climatologies for the Upper Indus Basin were developed on the basis of 1995–2017 precipitation normals obtained from four-gridded datasets (APHRODITE, CHIRPS, PERSIANN-CDR, and ERA5) and the quality-controlled high- and mid-elevation station observations. Monthly precipitation is estimated through the anomaly method at the catchment scale, and then, it is compared with the observed discharges over the 1975–2017 period for verification and detection of changes in the hydrological cycle. Running trends and spectral analysis on the precipitation gridded dataset were performed. The Mann–Kendall test was employed to detect the significance of trends whereas the Pettitt test was used to identify change points in precipitation and discharge time series. The results indicate that the bias corrected CHIRPS precipitation, followed by the ERA5, performed better in terms of RMSE, MAE, MAPE, and BIAS against the rain gauge observations. The running trend analysis exhibits a slight increase in annual precipitation, but it shows significant increase in winter precipitation. A runoff coefficient greater than one, especially in the glacierized sub-catchments of Shigar, Shyok, Astore, and Gilgit, indicates that precipitation is likely to be underestimated and glacial melt provides excess runoff volumes in a warming climate. Streamflow variability is found to be pronounced at the seasonal rather than at the annual scale. The annual discharges at Shyok, Gilgit, and Indus at Kachura gauges are slightly significantly increasing. Seasonal discharge analysis reveals more complex regimes, varying in different catchments, and its comparison with precipitation variability favors a deeper understanding of precipitation, snow-, and ice-melt runoff dynamics, addressing the hydroclimatic behavior of the Karakoram region and some weaknesses in the monitoring network at high altitude.

Highlights

The hydrological cycle change at the regional and global scale is a focus of current research, being the water cycle impacted by both climatic and anthropogenic factors not easy to identify
The mean annual bias corrected CHIRPS precipitation for the study domain was estimated as 536 mm yr-1 which is closer to the results obtained by (Cheema and Bastiaanssen 2012; Reggiani and Rientjes 2015; Rizwan et al 2019; Shafeeque et al 2019) who suggested corrected precipitation 523, 675+100, 550 and 593 mm yr-1 respectively in Upper Indus Basin (UIB) using various methods
The driest area is located over the South-Western part of the study domain along the Shingo and Zanskar basins followed by the upper part of Hunza, Shigar and the central part of Gilgit, while the highest precipitation values occur over the central part of Indus downstream, Astore, Shingo, and the upper part of Shyok

Summary

Introduction

The hydrological cycle change at the regional and global scale is a focus of current research, being the water cycle impacted by both climatic and anthropogenic factors not easy to identify. Precipitation is a key parameter to be monitored in glacial and snow-fed catchments such as the Upper Indus River Basin (UIB), where high-altitude precipitation monitoring is not continuous, showing the time series of observations some gaps, nor it is completely understood (Archer and Fowler 2004a). For this reason, a combined study of both precipitation and runoff provides a better insight into the variability of the water cycle in high mountain areas. UIB just upstream of Tarbela dam (draining an area of 163,528 km2) receives 70% of its annual flow from snow (26%) and glacial melt (44%) (Mukhopadhyay and Khan 2015)

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Discussion

Conclusion