An assessment of the water availability for mountain communities in the Parvati basin, Western Himalaya using a distributed hydrological model

The impact of changing climate on the Himalayas strongly influences the amount and timing of water available in the region. Millions of people in the downstream regions of Himalayan catchments depend on streams and rivers originating from the region for domestic consumption, livelihood, agriculture, and hydropower (Immerzeel et al., 2020). Many studies have highlighted the importance of snow and glacier melt towards water availability at the basin scale (Khanal et al., 2021; Prasad et al., 2019). However, the water availability at a much finer scale (i.e., to individual mountain communities) remains unquantified. Understanding the mountain communities' water availability is imperative to mitigate climate change impacts and ensure their water and food security (Kulkarni et al., 2021). In the present study, we aim to estimate the water availability to the communities in the Parvati Basin of Western Himalaya, including the contributions of snow and glacier melt, rainfall, and groundwater to runoff. The catchment has a total area of 1754 km² and consists of 279 glaciers which cover an area of 395.6 km². The volume of the glaciers and their mass balance are computed to understand the present state of the glaciers. The volume of the glaciers is estimated as 21.3 ± 3.8 km³ using laminar flow and scaling methods. The mass balance of the glaciers was estimated using the improved accumulation area ratio (IAAR) method as -0.44 ± 0.23 m w.e.a⁻¹. We simulate the daily runoff in the catchment using the Spatial Processes in Hydrology (SPHY) model, which is a fully distributed cryospheric-hydrological model. The volume and mass balance results are used to define the model's initial conditions and constrain mass loss during the simulations. Further, the study also aims to understand the role played by seasonal snow cover on the water available to the mountain communities. The outcome of this assessment would help to facilitate making informed hydrological and agricultural policies to mitigate the impact of climate change.