Pierre Viallet

Towards multi-scale integrated hydrological models using the LIQUID ® framework. Overview of the concepts and first application examples

Distributed hydrological models are valuable tools that can be used to support water management in catchments. However, the complexity of management issues, the variety of modelling objectives, and the variable availability of data require a flexible way to customize models and adapt them to each individual problem. Environmental modelling frameworks offer such flexibility; they are designed to build and run integrated models on the basis of reusable and exchangeable components. This paper presents the LIQUID^(R) framework, developed by Hydrowide since 2005. The purpose of developing LIQUID^(R) was to provide both easier integration of hydrological processes and preservation of their characteristic temporal and spatial scales. It suits a wide range of applications, both in terms of spatial scales and of process conceptualisations. LIQUID^(R) is able to synchronize different time steps, to handle irregular geometries, and to simulate complex connections between components, in particular involving feedback. The paper presents the concepts of LIQUID^(R) and the technical choices made to meet the above requirements, with focuses on the simulation run system and on the spatial discretization of process components. The use of the framework is illustrated by five application cases associated with contrasted spatial and temporal scales.

Use of Open-Source GIS for the Pre-processing of Distributed Hydrological Models

In distributed hydrological models, elementary modelling units are often derived from raster and vector geographical maps such as digital elevation models (DEM), land use and soil properties maps. Model pre-processing can be defined as the operations transforming raw GIS data into the adequate modelling units. This paper describes our experience with open-source GIS for these pre-processing operations through a set of examples. The softwares tested were PostGIS, OpenJump, OrbisGIS, GRASS, SAGA, MapWindow and QuantumGIS. The pre-processing operations dealt with DEM processing, topology corrections, and advanced editing of vector layers. None of the tested software provided a ready to use solution. However GRASS GIS appeared as the most promising candidate for performing all the preprocessing operations and automating them. Although sometimes tricky to handle by GIS non-expert users, open-source GIS allow easy tests and comparisons and therefore are well suited to research purposes.