Using spot flow measurements in a regionalized hydrological model to improve the low flow statistical estimations of rivers: The case of Réunion Island

Abstract

Study regionThis study is based on 22 gauged sites and 26 poorly gauged sites on the territory of Réunion Island, where quality hydrometric observations are available. Study focusInformation on streamflow is crucial for good water resources management and for respect ecosystems. For gauged catchments, the hydrology can be investigate from observations. For ungauged catchments, the lack of streamflow observations do not allow it. In this context, regionalized models for rainfall runoff are valuable resources. They have been widely employed as a means of predicting the streamflow of ungauged catchments. However, the performances of regionalized hydrological models seems to depend on the spatial density of available flow gauging networks. Using observations available on poorly gauged catchments to help to regionalize hydrological models can be another way of solving the data scarcity problem. This paper presents a framework for evaluating the use of spot flow measurements in a regionalized hydrological model when performing low flow statistical estimations in ungauged catchments. Three approaches are used to evaluate how to include spots flow measurements in the hydrological model calibration process. We tested too the addition of the poorly gauged sites in the regionalization procedure of the hydrological model. The effectiveness of the methods was measured by cross-validation. New hydrological insights for the regionIt is found that an increased accuracy using the regionalized model with help from spot flow measurements to predict streamflow time series in ungauged catchments. The increase is more moderate in low flow statistical estimations (QMNA5) than in medium and high flows.