Comparision of Hydrological Forecast Methodologies Applied to a Small Mountain Watershed

Abstract

A comparison of methodologies was carried out to develop an operational flow forecasting system for a mountainous basin. The case studied was the Boi river, which is located in a small mountainous watershed in southern Brazil. This watershed is part of a conservation unit well known for the ecotourism activities carried out in that place. Among the activities, the Boi river trail can be highlighted, which is carried out following the riverbed. For this reason, the development of an alert system for this basin can help in determining the trail's closure in situations where the water flow is strong and could present risks to tourists safety. Thereby, two different scenarios were considered for the development of the forecasting system. First, the flow forecasts were performed using SOPREVA and considered a horizon of 1 day (short term forecasts). The second scenario considered medium-term forecasts (1 to 10 days horizon) and utilized the HEC-RTS as a basis for developing the forecast system. In both cases, the forecasts were based on the ensemble precipitation estimates of GEFS. The obtained results showed that the actual alarm rates were 0.77 and 0.86 for SOPREVA and HEC-RTS, respectively, when considering a horizon of one day in advance. The evaluation of the medium-term forecasts presented good results of this system for horizons up to 3 days in advance. Finally, the results of both considered scenarios showed that the systems could be used as a basis for management of the Boi river trail.