| dc.description.abstract | Mountains occupy a critical role in the storage and supply of sufficient freshwater to livelihoods and ecosystems in lowland areas. This role is further emphasized by the term ‘water towers’. According to the global Water Tower Index (WTI) developed by Immerzeel et al. (2020), the most important water tower globally is the Indus Basin, where the water provisioning role of the mountains to the dry lowlands is especially large. Their Vulnerability Index (VI) additionally displayed the vulnerability of the Indus water tower to several indicators. The global scale of the study, however, prevented both the ability to draw conclusions on a scale smaller than the entire Indus Basin as well as the use of regional data. It is therefore unclear where the most important and vulnerable regions within the Indus Basin are located. Additionally, it is unclear whether a more regional approach would show larger spatial variety compared to the global WTI within the Indus Basin and whether it could potentially function as a first estimate and orientation tool for more complex and time-intensive hydrological studies.
Here, I apply the WTI and VI at subbasin scale for the Indus Basin to determine whether these are applicable at subbasin scale. This new approach is termed the regional Water Tower Index (rWTI), where a Supply Index (SI) and Demand Index (DI) are determined through several indicators. The VI consists of static and dynamic indicators, including government effectiveness, hydro-political tension, water stress, climate changes, and socio-economic changes. Eight delineated regional Water Tower Units (rWTU) are ranked by their importance and vulnerability using both global and regional data. The use of global data at subbasin scale enables a comparison to the findings by Immerzeel et al. (2020), while outcomes derived through regional data are compared to findings derived by more complex hydrological studies.
I conclude that the global WTI and VI are applicable at subbasin scale. Application of global data in the Indus subbasins already shows large variability in outcomes between the rWTUs and the Indus Water Tower Unit (WTU), showing that the global WTI-approach does not sufficiently consider the regional variety. The use of regional data changes the outcomes for all indicators, thereby improving the representation of spatial variability compared to global scale assessments, especially for the glacier indicator, snow indicator and the DI. Findings agree well with other studies, further demonstrating the applicability of the global WTI and VI at subbasin scale.
The applicability of the rWTI in other river basins could provide further evidence on whether the regional approach can function as an estimate and orientation tool for complex hydrological studies, although this study gives the first indication that it can. Beas/Sutlej is found to be the highest scoring rWTU, both due to having the second highest SI and having the highest DI, indicating it is the most important rWTU within the Indus Basin. This research could therefore be most useful for local political parties, inhabitants, tourists, and farmers of Beas/Sutlej and could be crucial in raising awareness on its importance and vulnerability. | |
