Surface water quality in the Netherlands needs to be improved in order to comply with European environmental legislation. For this purpose, the effectiveness of buffer strips on agricultural fields needs to be assessed. In Dutch agriculture, buffer strips are defined as dry, unfertilized field edges along open water systems (ditches). We established buffer strips on five experimental locations, differing in soil type (sand, clay, peat) and land use (grass, corn). At each location collector reservoirs have been installed in the ditches to measure the discharge and to sample the discharge water (water, Nitrogen species, Phosphorus species) from the field, both for a reference situation (fertilization up to ditch) and a buffer strip situation (5 m wide unfertilized grass strip). As the buffer strips were only recently established, it will take time before its effect will be clear in the discharge. In order to quantify the time-lag due to remnants of pre-bufferstrip N and P, we applied deuterated water (D₂O) as a tracer at the interface buffer strip – remainder of the field. In the reference situation we also applied D₂O in order to serve as a replicate. We then will determine the breakthrough in the reservoirs. As the locations are different from each other with respect to hydrology, the breakthrough is anticipated to occur at different times. We will present the first results of the breakthrough at the different sites. Also, we will compare measurements with a modeling effort to predict the breakthrough in a situation with deeply permeable sandy soil. The breakthrough data will be used to calibrate and validate a two-dimensional simulation model for water movement and nutrient transport.