• Jacob Skødt Jensen
  • Gitte Kjærsgaard Sørensen
4. term, Physical Geography, Master (Master Programme)
One of the biggest environmental problems in Denmark is the excess supply of nitrate to nature, primarily caused by the agricultural sector. This has resulted in poor conditions of aquatic and terrestrial habitats and a reduction in drinking water quality. Since the mid-1980s, the regulation of nitrate leaching has been based on general claims in danish laws, but new demands from the EU Water Frame Directive mean that there is a need for a more targeted environmental effort. Based on stronger legal regulations to protect nature, the aim of this project is to investigate how land use management can consider both environmental and agricultural interests through an Integrated land use management in rural areas. The small arable catchment Odderbæk in Northern Jutland is used as a case study with the aim to improve the environmental effort through a mapping of those areas that contribute to the nitrate supply to stream Odderbæk. A groundwater model was used to quantify the transport of nitrate from the root zone of the fields to the stream. By taking into account the reduction of nitrate in the oxygen-free part of the saturated zone (redox front) and in peat soil, it was possible to calculate a relationship between the amount of nitrate leaching from the root zone and the nitrate supply to the stream. Studies have shown that 75 % of the nitrate that is leached from the root zone is reduced between root zone and stream. The model calculations show that 60 % of the reduction occurs in the redox front and 40 % is caused by reduction in peat soil. Nitrate from drained areas and areas close to the stream provide the main nitrate supply to Odderbæk, while areas further away from Odderbæk do not provide any nitrate to the stream. The time delay that occurs between nitrate leaching from the root zones of the fields and nitrate input to the stream has been taken into account by using time corrected model calculations, which show that it is possible to simulate the nitrate supply to Odderbæk year by year. The model calculations have been used to set up scenarios that show the environmental effects of altered land use. Scenario 1 shows that a differentiation in land use by extensification of areas close to Odderbæk and intensifying the rest of the catchment can result in a 5 % reduction of the nitrate input to the stream without yield loss. Scenario 2 shows that extensifying areas that provides more than 70 kg nitrate/ha/year can result in a reduction of the nitrate supply to Odderbæk by 40 %. Scenario 3 shows that removing drains results in a higher nitrate reduction in peat soil and extensification that reduces the nitrate supply by 34 – 50 %. Implementing the principles of this method may be an administrative and economic challenge, because it is contrary to the general regulation. However, to improve the model, the method should furthermore include other aspects of land use management such as biodiversity, climate change, recreational interest, etc.
Publication date2009
Number of pages142
Publishing institutionAalborg Universitet
ID: 17652715