Background Water resources worldwide are under increasing pressure from overuse and pollution. In Greece, groundwater systems are threatened by a combination of excessive abstraction and chemical pollution. The Asopos river basin, which is located in the Region of Sterea Ellada, and the ‘River Basin District of East Sterea Ellada’ (RBD07), constitutes one of the most threatened water bodies (surface and groundwater) in the country. The unlimited use of water for agriculture, its abstraction for drinking purposes and uncontrolled industrial activity in the area have impacted significantly on the quantity and the quality of the water. Most importantly, the groundwater system of Asopos contains high concentrations of chromium and hexavalent chromium, which can reach levels of up to 100 microns/l. This has, understandably, caused increased public concern, particularly since part of the groundwater is abstracted for human consumption and irrigation purposes. The Ministry of Environment, Energy, and Climate Change has established Environment Quality Standards (EQS) for the area's surface water and Emission Limit Values (ELVs) for the relevant industries, but has not established respective threshold values (TVs) for the groundwater. However, the possibility that the background level of chromium in the aforementioned groundwater system is naturally elevated (due to the area’s geochemical characteristics) makes it difficult to determine the rational pollution TVs and propose and implement appropriate remediation technologies and measures. Objectives The aim of the project is to establish TVs for chromium in the Asopos river basin and to address delays in the implementation of the Groundwater Directive (GWD). Innovative technologies and methods will be applied to estimate the natural background levels of chromium in the Asopos river basin and appropriate remediation technologies will be then tested and evaluated. Specific objectives of the project are to: Evaluate the properties of the soil and the groundwater and assess their contribution to the potentially high natural background levels (NBL) of Cr(VI); Evaluate the effect of high NBL of Cr(III) and Cr(VI) on the determination of appropriate TVs; Develop a widely applicable (in other parts of Greece and the EU) and rational methodology for the determination of TVs, in accordance with the guidelines of Annex II of the GWD; Identify relevant polluting activities in the area and estimate the generated loads and their effective transport until they enter the aquatic environment; Demonstrate different technologies for the remediation of groundwater bodies with high concentrations of Cr(III) and Cr(VI); Establish a programme of measures (PoM) for the Asopos river basin, which will include the implementation of the most efficient chromium removal technologies as well as supplementary administrative and legal instruments, with the active participation of interested stakeholders. Achieve a stakeholder agreement on water resources management and protection; Exploit European best practices and know-how on water resources management, with particular emphasis on the implementation of the GWD. Expected results: A methodology for the determination of TVs for chromium compounds in groundwater bodies will be developed, in support of the Water Framework Directive 2000/60/EC and the Groundwater Directive 2006/118/EC; The improvement and rational management of water resources in the Asopos river basin and in the relevant groundwater body; Determination of NBL and TVs for chromium and hexavalent chromium for the groundwater system of Asopos; Quantification of chromium and hexavalent chromium removal efficiency using different remediation technologies; Adaptation of the PoM and determination of the effectiveness of the proposed measures on groundwater flow field and the chromium contaminant plumes, as well as the determination of the effects of climate changes on groundwater flow field and the chromium contaminant plumes; Strengthened sense of responsibility in the local community with respect to the protection and management of water resources.