Sustainable Restoration as a Tool for the Improvement of Water Quality in a Shallow, Hypertrophic Lake

Abstract

Sustainable restoration treatments were implemented with the simultaneous application of pro-ecological methods that complement each other to improve water quality in the shallow and heavily polluted Raczyńskie Lake. Phosphorus inactivation with magnesium chloride and Phoslock® was introduced along with biomanipulation. Physico-chemical and biological parameters were studied in 2015 (before restoration) and throughout 2018 and 2019 (during restoration). Water quality improved in the first year of treatment. An increase in water transparency, oxygen concentration above the bottom, a decrease of chlorophyll-a concentration and a reduction in cyanobacteria were observed. In the second year of treatment, a slight deterioration of water quality was recorded, probably caused by fewer phosphorus inactivation treatments and a shortened period of application. However, the deterioration of conditions is also characteristic of sustainable restoration at the beginning of the restoration process. The obtained results showed that sustainable restoration requires more than two years, and its scope and intensity should strictly depend on the pace of changes, determined on the basis of monitoring. In addition, improved water quality will have a positive impact on the recreational use of this reservoir.

Impounding Reservoirs, Benefits and Risks: A Review of Environmental and Technical Aspects of Construction and Operation

“…R16-Negative impact on the richness of the ecosystem and river water temperature. [115][116][117][118][119][120] The analyses concern 1 large and 4 small reservoirs in Europe. In addition, publication [116] reviews based on a large dataset.…”

“…In addition to planning measures and continuous monitoring of surface water quality, technical solutions can also be applied for reservoirs to achieve the expected ecological status or to revitalise neglected facilities (or parts of them) [115][116][117][118][119][120]. Increasing the feeding to the reservoir and reducing the time of water transport is an action that has the potential to remove a significant proportion of the pollution and counts as water reclamation [115]; however, this is not in every case technologically feasible or economically justified.…”

“…Depending on the characteristics of the site in question, it is possible to use artificial floating islands designed to make a positive contribution to a chosen aspect, such as through absorbing biogens, improving the habitat for aquatic organisms or optimising the temperature and aeration of the water [116]. To achieve improvement of water quality in the reservoir, chemical interference and interference with the structure of ichthyofauna species is acceptable, but this requires sustainable and long-term action to achieve lasting effects [117]. Local water purification (e.g., in an area used for tourism) can be achieved using point treatment systems [118], while a global improvement in the water quality of the entire site is achievable through the systematic discharge of deoxygenated hypolimnion water [119].…”