Theoretical Hydrographic Network (RHT)

Theoretical hydrographic network on the Vosges department. The French database (BD) Carthage® (acronym for the Database of Thematic Mapping of Water Agencies), which brings together entities related to hydrography, does not constitute in the present state a network in which the flow of water can be modelled. The construction of a simplified hydrographic network (natural maindrain) from the Carthage® DB (Pella et al. 2006) was a first nationally oriented network. This network, which accounts for approximately 92.800 km of watercourses, or just under one fifth of the entire Carthage® BD, is used by several water research projects. The natural main drain (DP) is not dense enough to have a good representation of French rivers. It consists mainly of medium to large courses at the expense of headwater streams. This representativeness problem has led us to the development of an extensive hydrographic network (EHR) that extends the RFP to smaller streams. As with the construction of the RFP, we have endeavoured to give priority to the natural arcs of the Carthage® BD. The network extension work was initiated by considering the DP as the reference axis of the future network. The method was to select the base arcs of Carthage® streams that connect directly to the DP. The ultimate goal is to achieve a denser hydrographic network, with perfectly joined arches, well-facing upstream downstream and the most natural (in the Carthage® classification) (Pella et al., 2008).The Extended Hydrographic Network (RHE) represents a total linear of 221.077 km. A theoretical hydrographic network (RHT) has been calculated from the RHE and the Alti ® BD of the IGN. The method used allows the network to be inserted into the digital field model, allowing the flow through the network to be taken into account. This RHT allows a better estimate of the watershed boundaries and the slopes of the sections. A major effort to correct the grid was done to bring the actual flow into line with the modelled flow. Environmental attributes were calculated for all network arches within the ESTIMKART model platform (Lamouroux et al. 2010). These include estimates of watershed surface areas, slopes, minimum monthly average and monthly flows, water modulus widths and heights, probability of presence of fish species. Confidence intervals around the calculated variables are provided. The spatial information layers used for the calculations are: — Normal AURHELY (period 1960-1990) from Météo-France — BD Alti IGN ® in step of 50 m — BD Carthage ® The RHT is distributed to: http://www.cemagref.fr/dynam Contact: [email protected]