Short description:

Nitrate leaching from agricultural areas is one of the major water resources management problems in Denmark. The efficiency of the existing general regulations is in average only 1/3, because 2/3 of the nitrate leaching from the root zone is reduced in the subsurface before reaching the streams. Today it is impossible to differentiate between vulnerable areas from where nitrate leaching reaches the surface water with very little reduction and robust areas where almost all leached nitrate is reduced. This is a serious constraint for designing cost-effective water management measures.

NICA will develop tools for assessing nitrate reduction in the subsurface between the root zone and the streams and methodologies for assessing at which spatial scales such tools have predictive capabilities. A new instrument will be developed for airborne geophysical measurements, MiniSkyTEM, dedicated for identifying geological structures and heterogeneities in the upper 30 m. Furthermore, a new geophysical method, MRS, will be introduced and the two novel geophysical methods will be tested against field data. State-of-the-art and novel hydrological models (DAISY, MIKE SHE/MIKE11, HydroGeoSphere, RWHET) will be applied and the effect of geological heterogeneity will be analysed by use of stochastic geological realisations using TProGS. A new concept, Representative Elementary Scale (RES), will be developed for assessing the minimum scale at which models, with a given data input, potentially have predictive capabilities. The studies will be conducted in a 5 km2, densely instrumented catchment (Lillebæk) and tested in a 100 km2 catchment (Norsminde Fjord), where farmers and authorities will be actively involved in evaluating possible measures for reducing the nitrate load to surface water in a cost-effective manner. The economic gain from a cost efficient location of the measures will be evaluated.