Modified rainfall-runoff model for bifurcations caused by channels embedded in catchments

Abstract

The particularity of 'Vlasina' hydropower plants catchment is a big number of gravitation channels used to collect the water from neighboring natural catchments. The overall catchment size is thus increased, compared to the natural catchment. At the bifurcations where the gravitation channels with mild slope are intersecting the steep natural hydrographic network, the natural surface and subsurface water flows are significantly altered. The channel which intersects the river flow will hold the water at higher elevations, filling the storages or transferring the water to another catchment. Under such conditions, the concept of rainfall to runoff transformation in SWAT-based model had to be modified in a way that the channel does not capture all the water from the natural watercourse, but will allow a certain volume of water to run downstream, both for the surface and subsurface flow. New SWAT-related objects were introduced: HPN (hydro-profile on the natural watercourse), HPC (hydro-profile on the channel), HPI (hydro-profile on the channel, the intake) and HPS (storage hydro-profile). For each object the water balance and transformation equations were derived, adapting SWAT model to simulate the flow in the bifurcating network of natural streams and channels. The new model was calibrated on the catchment area of the 'Vlasina' hydropower plants system. This paper presents the adaptations of the SWAT-based model and results of its application on the northern part of the system (catchments of the channels 'Strvna' and 'Čemernik').