The ORACLE observatory is created to work on the Research Observatory of the « Grand Morin » and « Petit Morin » river catchments, and particularly to develop studies on floods, low water periods, water quality and the impact of human activities on the environment. The elaboration of a Research Observatory in Environment concerning the Orgeval , Grand Morin and Petit Morin basins which have been continuously studied for many years (since 1962 for the Orgeval), enables us to better understand hydrological processes in anthropized rural environments with a sedimentary dominant. The ORACLE observatory is articulated around the three following points: Observation and modeling of water and pollutants transfer processes at various scales; Hierarchisation of these processes ; Observation and modeling of streamflow to improve risk forecast. Development and validation of methodology; Strategies of measurement and consideration of the modes of representation of the systems: Optimization of the data acquisition methods ; Assimilation; Optimal scale of representation; Conceptualization. The objective of this observatory is to identify the processes involved in the transfers of flow and pollutants at various scales, by the creation of a perennial device of observation of the variables and parameters concerned. The aim is to improve water quality, forecast and prevention of flood risks related to extreme hydrological events. Accordingly, the occurence of novel data acquisition methods (hydrological radars, satellites), will make it possible to study the contribution of new spatialized data within modeling.