Hydrological response to environment change in Himalayan watersheds: Assessment from integrated modeling approach

Abstract

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Hydrological Modeling and Characterization of the Khanpur Watershed, Pakistan

“…The Khanpur watershed area follows an almost dendrite (treelike) pattern of streams; this indicates that most of the rocks in the watershed are homogenous and layered (Ahmad et al 2015). The presence of numerous first‐order tributaries (111 in total), described in Table 5, indicates that the watershed area is underlain by impermeable material, which is also confirmed via other parameters such as drainage density and stream density (Table 4).…”

“…A compactness factor of 1.2 expresses the shape of the basin used by Horton, with the value ranging from 0 to 1. Usually, a shape factor of 1 represents an ideal case or maximum symmetry, such as a circle, sphere, square, or cube (Ahmad et al 2015).…”

Current Practice and Recommendations for Modelling Global Change Impacts on Water Resource in the Himalayas

“…The anthropic impacts are also different. From the few studies that report on them, the Indus river is generally the most affected by infrastructure such as dams [42,86,87], canals [88] and hydropower generation structures and diversions [80]. However, none of the studies model the influence of such infrastructures on the spatio-temporal availability of water resources across the catchment or at least do not report them.…”

“…Many studies directly address climate change as their primary objective through the simulation of impacts on water resources [2,29,31,81,[89][90][91][92]. In contrast, land use change as a component of global change and driver of future water availability and irrigation demand received minor attention [78,86]. The recognised limitations in modelling approaches and in the current understanding of hydrological processes in the Himalayas leads to a significant number of studies aiming at improving the simulation of current hydrological processes (i.e., model performance) [15,82,83,[93][94][95][96] or focusing on understanding the relevance of each flow component in the hydrological regime (i.e., basin behaviour) [4,80,[97][98][99] as a basis for future application to global change impact assessment.…”

“…Ideally, direct field measurements should be used [84,92], but this option is limited by the lack of data availability in space and time. The possible bias introduced by subjective initial conditions can be reduced by using a warm-up period, which in the reviewed studies ranges from 1 year or less [15,81,114,131] to 6 [86,96] or 10 years [93]. While warm-up periods of a few years are sufficient for most hydrological storages, they may be too short in the case of glaciers as their response time is in the order of decades in the Himalayas [18].…”