2.2.1. Hydrological Models

The description of basin hydrology uses the SPHY [16,17] and Wflow [18] models. These are fully distributed models implemented on a 1 km by 1 km grid. SPHY describes the hydrological process in the mountainous areas of the Himalaya and was selected as it is specifically designed for glacier and snow hydrology and it has previously been successfully applied to the Himalaya [19]. Rainfall-runoff for the non-mountainous part of the Ganga Basin were simulated with Wflow—a general-purpose hydrological model. River discharges from SPHY provide inputs to Wflow. Both models use the following static input data:


SPHY also uses a map of glacier outlines and distinction between debris-covered and debris-free glacier surfaces from [26].

Both models use the following distributed meteorological data:


The concepts used by SPHY and Wflow to simulate river flow are described in [16,17] and [18] respectively. They produce gridded, daily flows across the entire model domain, which are input to the water resources model (see Section 2.2.2), and gridded, daily infiltration rates, which are input to the groundwater model (see Section 2.2.4).
