The environmental influence of forestry, agriculture and urban activities on the hydrological conditions in a small river basin in southern Sweden and the effects on the river water quality are analyzed and quantified on different time scales. The emphasis is on the river flow fluctuations and the transport of nitrogen to the sea. Different measures for decreasing the load of nutrients are discussed. It is shown that if wetlands are re-established in rural areas and techniques for water treatment are introduced, it is possible to reduce the nitrogen transport to the sea by 60%. However, this reduction would have little influence on improving the nutrient status of coastal waters.