An Application of Distributed Hydrological Model, YHyM/BTOPMC to Gin Ganga Watershed, Sri Lanka

Abstract

Modelling approach is a useful tool which provides information on spatial distribution of basin hydrologic components. In that context distributed hydrological models play a vital role in efficient planning and managing water resources systems. But their applications are partly limited due to the requirement of large amount of data which are not always available and difficulties in obtaining such data due to bureaucratic constraints. Global public domain data sets have become increasingly available on the internet and it is appropriate to make use of such data which can often be supplemented for ground-based data. The objective of this study is to investigate the applicability of the distributed hydrological model, YHyM/BTOPMC to simulate the major hydrological characteristics in Gin ganga watershed utilizing the global data sets readily available in public domain along with the local available rainfall and discharge data. Gin ganga is a river which is one of the main sources of water supply to the southern region of Sri Lanka. It’s catchment entirely lies within the wet zone of the country and frequently subjected to flooding during the rainy seasons. Hence, it is vital to comprehend the hydrology of the watershed in order to gain knowledge on current and future hydrological conditions. In the study, YHyM/BTOPMC model performance was evaluated by the Nash-Sutcliffe Efficiency (E) and the volume ratio of simulated discharge to observed discharge (Vr). The results show that the overall hydrological behaviour of the Gin ganga watershed is adequately simulated by the model. Further the results are discussed in the context of how the model simulation results replicate the temporal variation of basin hydrological characteristics such as ground water saturation deficit, soil moisture states, base flow etc.