Targeted water release to flush fine sediment out of bypassed section of the Durance River downstream four dams

International audienc

Targeted water release to flush fine sediment out of bypassed section of the Durance River downstream four dams

International audienc

From flushing flows to (eco)morphogenic releases: evolving terminology, practice, and integration into river management

International audienc

Targeted water releases to flush fine sediment out of a bypassed reach of the Durance River downstream of four dams

The Durance River is a highly regulated, gravel-bed river with a naturally high fine sediment load in southern France. EDF operates eight dams along the regulated main stream channel (218 km from the Serre-Ponçon Dam to the confluence with the Rhône River), that divert water to 16 hydroelectric power plants via a canal. Flow regulation has contributed to fine sediment accumulation (clogging) in the Durance River. In addition to a recent increase in minimum flows has implemented targeted water releases at four out of eight dams to simulate floods and reduce clogging to restore river function for fishes and invertebrates, The timing of these releases is defined for each dam based on the spawning period of target fish species. During the release, TSS, O2, T, H, and conductivity are measured continuously. Before and after each release, clogging (superficial/interstitial) is measured. This monitoring program showed that several of the releases were not effective on surface clogging inducing a loss of water or resulted in effects contrary to those sought, although this was not reflected in the biological results. These results indicate that two parameters must be taken into account to determine a priori the need to carry out releases: the hydrology observed during the year and the initial level of clogging. Artificial flood releases are increasingly being used a management tool to mitigate hydropower impacts on river hydromorphology and ecology. This experimentation shows that it is necessary to carry out these types of operations in an adaptive management context. At this time, the results obtained do not lead to clear conclusions regarding their efficacy, mostly as a result of strong interannual variation in hydroclimatic conditions, which have a strong influence on initial conditions and resulting outcomes. Furthermore, it is important to incorporate this field measurements and not rely solely on turbidity gauging stations to evaluate efficacy

From flushing flows to (eco)morphogenic releases: evolving terminology, practice, and integration into river management

International audienc

Targeted water releases to flush fine sediment out of a bypassed reach of the Durance River downstream of four dams

The Durance River is a highly regulated, gravel-bed river with a naturally high fine sediment load in southern France. EDF operates eight dams along the regulated main stream channel (218 km from the Serre-Ponçon Dam to the confluence with the Rhône River), that divert water to 16 hydroelectric power plants via a canal. Flow regulation has contributed to fine sediment accumulation (clogging) in the Durance River. In addition to a recent increase in minimum flows has implemented targeted water releases at four out of eight dams to simulate floods and reduce clogging to restore river function for fishes and invertebrates, The timing of these releases is defined for each dam based on the spawning period of target fish species. During the release, TSS, O2, T, H, and conductivity are measured continuously. Before and after each release, clogging (superficial/interstitial) is measured. This monitoring program showed that several of the releases were not effective on surface clogging inducing a loss of water or resulted in effects contrary to those sought, although this was not reflected in the biological results. These results indicate that two parameters must be taken into account to determine a priori the need to carry out releases: the hydrology observed during the year and the initial level of clogging. Artificial flood releases are increasingly being used a management tool to mitigate hydropower impacts on river hydromorphology and ecology. This experimentation shows that it is necessary to carry out these types of operations in an adaptive management context. At this time, the results obtained do not lead to clear conclusions regarding their efficacy, mostly as a result of strong interannual variation in hydroclimatic conditions, which have a strong influence on initial conditions and resulting outcomes. Furthermore, it is important to incorporate this field measurements and not rely solely on turbidity gauging stations to evaluate efficacy

Inventory of the Ichthyofauna of the Mpem and Djim National Park (Center, Cameroon) Provides Baseline Data for a Conservation Project

The intense anthropization of the Sanaga basin requires an acceleration of research on biodiversity and the conservation of its aquatic resources. In this framework, the ichthyofauna of the Mpem and Djim National Park (MpDNP) has been inventoried for the first time. The fish were sampled from 2017 to 2021 using diverse experimental fishing gears. A total of 79 species classified into 39 genera, 14 families, and 8 orders have been identified in the MpDNP. This ichthyofauna represents 46.7% of the 169 freshwater fish species known in the Sanaga basin. It contains 15 (62.5%) of the 24 endemic species reported in this basin, among them two Endangered and three Vulnerable species known on the IUCN Red List. Furthermore, two non-indigenous species have been inventoried. Siluriformes (36%) and Characiformes (22%) are the most represented in the MpDNP. It is suggested that the issues for conservation in this park must be focused as a priority on 15 endemic species, which may be ranged into two national protection classes A (5) and B (10), then on those in class C, which will be identified posteriorly as supplementary priorities for the offset of the residual impacts of the Nachtigal upstream hydropower plant development