ABSTRACT
To understand, characterize and/or model the different phenomena and processes associated with hydrological systems, data are required. They can be divided into two categories:
• time series and historical data used to follow, in a continuous or discontinuous manner, the temporal evolution of meteorological conditions (e.g., precipitation, temperature, wind) and state variables of the hydrological system considered (e.g., discharges, soil moisture, water table level, snow cover, snowpack depth and water equivalent, storage level in natural and artifi cial reservoirs);
• geographic (i.e., spatial) data used to describe, at a given time, the studied hydrological system (e.g., physiographic characteristics of the drainage basin, characteristics of the hydrographic network, hydraulic structures).
