b'New methods for third generation river basin management plans under the water Framework Directive - assessment of the impact of surface water from groundwaterNilsson B1, Sndergaard M2, Johansson LS2, Olsen A2, Kazmierczak J1, Thorling L1 andTroldborg L11Geological Survey of Denmark and Greenland, Department of Hydrology, Copenhagen, DK-1350, Denmark2Aarhus University, Department of Bioscience, Silkeborg, DK-8600, DenmarkThe Danish Environmental Protection Agency has initiated several research and development projects to provide knowledge and determine methods that can assess how and to what extent, the content of pollutants and water abstraction in a groundwater body can affect the state of associated targeted surface water bodies or groundwater dependent terrestrial ecosystems (GWDTE) in Natura 2000 areas. The presentation will be focusing on the groundwater- lake sub-programme, where the interaction between groundwater and lakes is simulated with The National Water Resources Model (DK-model) for lakes with a surface area larger than 100 hectares. The spatial resolution of the DK-model is today too coarse to estimate the hydraulic contact between groundwater and lakes smaller than 100 hectares, thus a tool box of field site specific methods was developed to assess the quantitative impact on lakes smaller than 100 hectares. A new method consisting of a five step approach has been developed to assess the chemical and quantitative status. The method was tested in four lakes with good chemical and quantitative datasets in Denmark. The test of the stepwise method on both the quantitative chemical effect in all test lakes could be carried out to the steps four or five. The step five of the chemical effect is dominated by an expert assessment. There have been discrepancies in the methods used to determine the percentage of groundwater seepage into lakes smaller than 100 hectares. The development of a simple quantitative method for calculating the diffuse nutrient load of a lake may be needed. In addition, there is a need to develop a tool for assessing when the 50% diffuse nutrient load of a lake has been exceeded.This study was carried out last year in a collaboration between The Geological Survey of Denmark and Greenland & Aarhus University.38'