Assessment of Spatial and Temporal Flow Variability of the Indus River

Abstract

Considerable controversy exists among researchers over the behavior of glaciers in the Upper Indus Basin (UIB) with regard to climate change. Glacier monitoring studies using the Geographic Information System (GIS) and remote sensing techniques have given rise to contradictory results for various reasons. This uncertain situation deserves a thorough examination of the statistical trends of temperature and streamflow at several gauging stations, rather than relying solely on climate projections. Planning for equitable distribution of water among provinces in Pakistan requires accurate estimation of future water resources under changing flow regimes. Due to climate change, hydrological parameters are changing significantly; consequently the pattern of flows are changing. The present study assesses spatial and temporal flow variability and identifies drought and flood periods using flow data from the Indus River. Trends and variations in river flows were investigated by applying the Mann-Kendall test and Sen’s method. We divide the annual water cycle into two six-month and four three-month seasons based on the local water cycle pattern. A decile indices technique is used to determine drought and flood periods. Overall, the analysis indicates that flow and temperature variabilities are greater seasonally than annually. At the Tarbela Dam, Indus River, annual mean, maximum, and minimum flows decreased steeply from 1986–2010 compared to the 1961–1985 period. Seasonal flow analysis unveils a more complex flow regime: Winter (October–March), (December–February), and spring (March–May) seasons demonstrate increasing flows along with increasing maximum temperature, whereas summer (April–September), (June–August) and autumn (September–November) showed decreasing trends in the flow. Spatial analysis shows that minimum discharge increased at the higher elevation gauging station (Kharmong, 2542 m.a.s.l.) and decreased at the lower elevation gauging station (Tarbela). Over the same timeframe, maximum and mean discharges decreased more substantially at lower elevations than at higher elevations. Drought and flood analysis revealed 2000–2004 to be the driest period in the Indus Basin for this record.

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

“…Except for Kharmong and Astore, the annual trends of the SSC in the glacier-and snow-dominated basins of the UIB decrease in the months of July, August, and September, which is due to less snow/glacial melt in the cooler summer, as was reported by researchers [7,8,38,39]. In contrast to the SSC trend, an insignificant increase or no change in annual flows is detected, as is shown in Tables 6 and 7.…”

“…The trends induced by climate change on the discharges of various sub-catchments have been widely reported by many researchers [7,8,38,39], however, scientific literature on the spatio-temporal variation of SSC is far less extensive. Ali and De Boer [18] analyzed the spatial distribution of sediment in the UIB by dividing the region into three zones: upper snow-and glacial melt-dominated zone, middle snow-/glacial melt-, and rainfall-dominated mixed zone, and lower rainfall-dominated zone.…”

Analysis of Streamflow Variability and Trends in the Meta River, Colombia

“…Some of these possible effects include: underestimating design flow rates for hydraulic structures, assigning water rights beyond the capacity of the river to supply them, and consequently, over-exploitation and insufficient water to sustain the ecosystems and other uses [2]. The importance of this research topic is supported by many recent papers on the subject, as hydrological trend assessments at different timescales (decadal, interannual, annual, seasonal, monthly) have been conducted for watersheds across the world [3][4][5][6][7][8], and they serve as evidence in the debate on climate change [9] and non-stationarity. It is worth mentioning the study by Su et al [10] is of interest in the current context, where these authors evaluated data from the year 1948 to 2004 for detecting long-term streamflow trends in 916 large rivers all over the globe.…”

An Assessment of the Pakistan Water Apportionment Accord of 1991

“…Climate and flow variability from climate change have been found to affect the productivity of irrigated agriculture in the Indus Basin, with the overall net economic benefit from irrigated agriculture expected to change significantly [34,35]. Studies consequently point to Pakistan experiencing acute shortages of water negatively affecting those dependent on the Indus River and exacerbating conflicts among provinces [18,36,37].…”