Background Important priorities of Polish environmental policy are related to the requirements set out by the Water Framework Directive (2000/60/EC), with special attention paid to urban water ecosystems because of their importance for the quality of life. The head of the Bzura River and the system of Arturówek Reservoirs are used for recreational activities by the citizens of Łódź in central Poland. The Arturówek complex consists of three interconnected reservoirs: upper (area 1.08 ha), middle (2.58 ha) and lower (3.05 ha). The section above the Arturówek Reservoirs collects storm water, while the farthest upstream sewer discharging into the river occurs above the reservoirs. Objectives The main goal of the EH-REK project was to use the concept of eco-hydrology to restore the Arturówek Reservoirs. The bowl of the upper reservoir is currently used as a settling pond, but the project foresaw its conversion into a sedimentation-biofiltration system, leaving the lower and middle reservoirs for recreational purposes. The project aimed to introduce an innovative approach to consolidate knowledge on the functioning of urban water ecosystems; explore planning and decision-making methods used in the management of urban water ecosystems; develop and use eco-hydrological technologies to comply with the requirements of the Water Framework Directive (WFD); and implement a system for training, dissemination, and multi-stakeholder co-operation. Results The EH-REK project completed all its actions and achieved all its objectives successfully. The project team constructed and tested an innovative and highly-transferable eco-hydrological system to rehabilitate the Arturówek Reservoirs in the city of Łódź, which contributed to improving the quality of water in the reservoirs. To this end, the project team removed 11 000 m3 of bottom sediments from five reservoirs located in the project area, constructed buffer zones, planted macrophytes and constructed gabions (mesh cages located on the inlets for storm waters into the reservoirs), installed natatorial (floating) plant mats in the reservoirs, repaired a dam, and implemented the finalised sedimentation-biofiltration system upstream of Arturówek. The scope of the earthworks implemented by the beneficiaries was wider than foreseen. In addition to the three Arturówek Reservoirs, bottom sediments was also removed from reservoirs located above Wycieczkowa Street in Łódź. Innovative hydrological modifications in the river increased the self-purification capacity of the Bzura River above the Arturówek Reservoirs. The efficacy of the earthworks and the structures exceeded the planned level of 20%. These methods have a minimal impact on the environment because they use natural processes of water self-purification, therefore they are suitable for sites frequented by people. One of the main outputs of the project was an Internet tool to support the decision-making process and to help local authorities select the best practices for water protection on their territory. This user-friendly tool is available in Polish and English on http://model-en.arturowek.pl/, therefore, it can be used by local authorities in different EU countries. Environmental and socio-economic benefits derive from the substantially improved water quality in the Arturówek Reservoirs, which is one of the main recreational areas in Łódź. In 2014 and in 2015, no blooming of blue-green algae and no cyanobacterial toxins were observed. The concentration of the cyanobacterial toxins in the water decreased from 57 ppm to 0.25 ppm in 2015. During these summers, the beach located at the biggest reservoir was visited by thousands of tourists. The project’s work has the potential for creating new jobs - its implementation helped to open a new small restaurant at the site and increased the number of people who stay in a nearby hostel. A survey carried out among people who visited the Arturówek site showed that the number of respondents who believed that the quality of water was good increased from 2-3 % in 2010 to 42% in 2015. At the same time, the number of respondents who believed that the quality of water is insufficient decreased from 68% in 2010 to 13% in 2015. This observation was confirmed by the results of the monitoring, according to which the pollution in water outflow from the upper Arturówek Reservoir was reduced by approximately 70% (20 % was expected). The sediment- biofiltration system improved the storm water quality by 60-70% (50% was expected), with the construction of bio-filtration zones additionally improving the quality of water in the Arturówek Reservoirs. Monitoring showed that the amount of removed pollutants increased in the places where the new buffer zones were constructed. Reduction of the contamination effluent will help to implement the requirements of the Water Framework Directive. The project produced a Framework Strategy of water ecosystem rehabilitation in Łódź, in which they presented the activities which should be implemented to ensure the good ecological status of the waters (ponds and rivers) in Łódź. They also established good cooperation with local stakeholders and administration responsible for the quality of water in the city of Łódź. This will increase the probability that the proposed activities will be implemented in the coming years. The local authorities are using the new Framework Strategy to improve the quality of water at two other sites (Stawy Jana and Stawy Stefańskiego). EH-REK raised the environmental awareness of local authorities and citizens in Łódź, who accepted the extensive earthwork at Arturówek because the results demonstrated that they improved the quality of water. Thanks to the reduction of blue-green algae and cyanobacterial blooming, the beach could be used throughout the year. Therefore, the project has a large demonstrative value and strong replicability potential, showing that it is possible for measures aimed at protecting the environment and local development to complement one another. Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).