Romania and Hungary have launched an action program to accomplish the EU Water Framework Directive 2000/60/EC (WFD) which requires toprevent further deterioration of groundwater. They harmonised their activities also on the GWBs-RO-HU water body in Koros-basin where the information is limited not sufficient for establishing the needed arrangements. The studied area has one million inhabitants, having industrial activities and closed factories endangering the water body. The rate of the hazard is unknown.Establishing the Water Management Plan of the trans-boundary water body needs a lot of measurements and overall knowledge. In the Koros-basin along the frontier the groundwater part bodies compose connected systems but not known the rate and the character of the coherency.Idea of the project: the joint Crisuri Project, which gave bases to the plan of outside-border water management for the catchment area of the Crisuri, in the project area has closed. Relatively few new results came alive in the frame of this joint groundwater waterbody characterization, these ones are mainly for the shallow, holocene water bodies: 6 geological section, groundwater surface contour map, the groundwork of the joint monitoring network, the chemical and quantitative estimation of the wate rbodies. After these results the need of cognition for the deeper, pleistosenic-pannonic water bodies has risen.The general objective of the project is trans-boundary water body research for efficient protection.Target groups: Population: about 1 Million people on both sides of the border. Water need of the inhabitants is about 120.000 cubic meter per day, where the proportion of water coming from subterranean water resources should be as high as possible.Other beneficiaries: institutes and industrial facilities, organizations, local governments of the affected counties and settlements.The main specific activities and results of the project are:Within the frames of this project we perform a complex research focused on the GWBs RO-HU subsurface water body, divided by the border between Romania and Hungary. The primary scope of the research is to build up a knowledge base that contains as much information as possible about the geological and environmental rules and relationships that directly or indirectly affect the state and quality of this water resource. The research work includes elaboration of local and over-border measures that should be taken to maintain and improve the water quality. Our targeted activity area is the part of this water body that falls onto the competence area of the Hungarian water directorate TIKOVIZIG and the Romanian Bihor County, including the basins of the Berettyo and Sebes-Koros rivers. Exploration of the hydro geologic, hydraulic and geo-chemical relationships is achieved through standardized debit, water level and analytic measurements performed in existing fountains and springs on both sides of the border. The collected data also serve to identify water body parts using cluster analysis, and to delineate flow-in, flow-through and out-flow zones with regional models. We select three sample regions from each zone type and examine the effects of anthropogenic activity, soil utilization and socio-economic development on the accumulated water resource. We also examine the possibility and effect of the actions necessary to keep the water body in its good quality state.