National Observatory of Staircases

The national observatory of drawdowns (ONDE) characterises summer lows by l' visual observation of the level of ' flow of certain rivers of metropolitan water. It pursues the dual objective of building a stable network of knowledge on summer lows and of being a tool to help anticipate and manage crisis situations. It thus strives to: • Acquire robust and sustainable data, homogenise results and disseminate them to managers and decision-makers; • Edit map comparison points over time, which can also be used in crisis management. The acquisition of low data allows the analysis of the situation of the moment, but also the analysis of the evolution of hydrological phenomena over time, over the short or medium term, thus helping the public authorities. The chronicles of ' observations are also of interest to scientists, e.g. for the development of models of forecasting of tidal; or the understanding of water-to-river relationships. The data collected thus offers the opportunity to better take into account climate change and its impact on watercourses. The Onde system has taken over from the historical ROCA (Network of Assec crises) and RDOE (Departmental Network of Stairs) at the national level in 2012. It is one of the tools listed in the circular of 18 May 2011 on exceptional measures to limit or suspend the use of water in times of drought. The stations of the Onde device are mainly positioned at the top of the watershed to complete the hydrological data on hydrographic hairs not covered by d' other existing devices, but also to provide the information available to the water managers (e.g. HYDRO and ADES bank). Each department is covered by at least thirty stations of observation. Today, the network has more than 3,300 stations. On the other hand, there is no station in the departments of the city of Paris, Seine-Saint-Denis and Hauts-de-Seine, which are mostly urban. __Origin__ The network of stations s' organises according to two types of monitoring, whose objectives and implementation modalities differ: • The usual monitoring is aimed at the establishment of a knowledge network. The usual places of observation must be stable over time, so as to constitute historical datasets, allowing the estimation of the intensity of summer lows of one year compared to previous years. To this end, all stations are monitored regularly at fixed periods and frequencies, defined at national level. The usual monitoring is thus carried out monthly, systematically on all metropolitan departments, between May and September, as close as possible to the 25th of each month (more or less 2 days away); • Complementary monitoring contributes to better management of situations deemed sensitive. Its activation can be triggered at any time (including outside the period May — September) by the Department Prefects (MISE) or by spontaneous decision of Onema Departmental Services. It can also be at the scale of the basin if the situation requires it (in this case, on the initiative of the prefects co-ordinating basin) or at the national level if a state of crisis justifies it (by the Ministry responsible for the environment). Additional monitoring can be carried out at only part of the stations (e.g. on a watershed particularly impacted by water withdrawals). The frequency of prospecting is left to the #x27; appreciation of local actors, the maximum can be weekly at the worst of the crisis. __Partner organisations__ ONEMA __Links annexes__ * [National lowlands observatory by campaign of #x27; observation](http://onde.eaufrance.fr/acces-aux-donnees) * [National Lowlands Observatory: URN consultation](http://onde.eaufrance.fr/content/url-de-consultation) * [National Lowlands Observatory: WMS and WFS streams](http://onde.eaufrance.fr/content/services-web) [See this page on geo.data.gouv.fr](https://geo.data.gouv.fr/fr/datasets/58b91584c3afac0bbd54c5e7f38a29bb4b1aeab5)