Using hydrological models and Geographic Information Systems for water resources evaluation: GIS-VISUAL-BALAN and its application to Atlantic basins in Spain (Valiñas) and Portugal (Serra da Estrela)

Abstract

[Abstract:] This paper presents a distributed hydrological model for the evaluation of water resources, which has been obtained by extending the capabilities of VISUAL-BALAN V2, a lumped hydrological code developed by the University of La Coruña, and coupling it to a GIS. VISUAL-BALAN is a lumped hydrological model, which solves the water balance equations in the soil, the unsaturated zone and the aquifer. It requires only a few parameters and incorporates user-friendly interfaces for data input and post-processing of results. It evaluates hydrological components in a sequential manner. Besides the balance in the upper soil the code also solves the water balance equations in the unsaturated zone and the underlying aquifer. This allows the computation of daily groundwater levels, as well as basin water discharge rates. Computed heads and streamflows can be compared to measured values for the purpose of model testing and calibration. VISUAL-BALAN accounts for irrigation sources and return flows. It also allows for snow precipitation, melting and runoff. Two advanced options have been developed: (1) automatic parameter estimation using groundwater level and streamflow data; and (2) sensitivity analyses of the main components of the water balance with respect to model parameters.