Initial results of remediation activities to restore hypereutrophic Villerest Reservoir (Roanne, France)

Abstract

We examined the impacts of remediation activities aimed at improving the water quality of hypereutrophic Villerest Reservoir, in which Microcystis aeruginosa dominated during the summer. We also compared nutrients and chlorophyll a data from this study with the results of a previous study on the reservoir. Between the two studies, the nitrogen and phosphorus loads into the reservoir from the main tributary decreased by 70% and 80%, respectively. Within the reservoir, the quantities of ammonianitrogen were similar in the two studies, and the total nitrogen was significantly higher in this study compared to the initial study. Both the phosphate-phosphorus and total phosphorus concentrations decreased significantly between the two studies. However, the statistically significant decrease in phosphate-phosphorus and total phosphorus did not always lead to a significant decrease in chlorophyll a concentrations. The nitrogen/phosphorus mass ratio during the present study remained well above five, the critical value below which summer blooms of Microcystis aeruginosa were observed in Villerest Reservoir. These study results indicated that the remediation activities being used to improve the water quality of Villerest Reservoir were off to a good start.

Estimate of the Eutrophication Process in the Gruža Reservoir (Serbia and Montenegro)

“…Fluctuation of the water level in reservoirs leads to variation of the littoral zone, which can adversely affect development of macrophytes and spawning of fish. Great caution is needed in employing biomanipulation of the food web because it is difficult to predict the development of water quality due to spatial and temporal variations in reservoirs and lakes [51].…”

Eutrophication mitigation in rivers: 30 years of trends in spatial and seasonal patterns of biogeochemistry of the Loire River (1980–2012)

“…At the headwaters, Chl a concentrations remained below 30 µg L −1 between 1981 and 2012. It has been shown in other studies that in the Upper Loire reservoirs which have always been eutrophic since the 1980s (Aleya et al, 1994;Jugnia et al, 2004), the phytoplankton assemblage is lake-like and these species do not survive very long in the turbulent and quite turbid river downstream (Abonyi et al, 2011(Abonyi et al, , 2014, explaining why Chl a remains at low levels. In the lowest section of the Upper Loire (station 9), Chl a was higher but showed a decreasing trend for the whole period.…”

Water quality trends in Polyphytos reservoir, Aliakmon River, Greece

“…Human activities on the watershed also influence the trophic status of the reservoir and contribute to the impairment of their water quality, resulting in limitations in water use (Gikas et al 2006a;Olvera-Viascán et al 1998). Therefore, in many cases of eutrophic reservoirs, efforts are undertaken to restore the system, aiming at improving its water quality (Jugnia et al 2004).…”