Uncertainties in river basin data at various support scales ? Example from Odense Pilot River Basin

International audienceIn environmental modelling studies field data usually have a spatial and temporal scale of support that is different from the one at which models operate. This calls for a methodology for rescaling data uncertainty from one support scale to another. In this paper data uncertainty is assessed for various environmental data types collected for monitoring purposes from the Odense river basin in Denmark by use of literature information, expert judgement and simple data analyses. It is demonstrated how such methodologies can be applied to data that vary in space or time such as precipitation, climate variables, discharge, surface water quality, soil parameters, groundwater abstraction, heads and groundwater quality variables. Data uncertainty is categorised and assessed in terms of probability density functions and temporal or spatial autocorrelation functions. The autocorrelation length scales are crucial when support scale is changing and it is demonstrated how the assumption used when estimating the autocorrelation parameters may limit the applicability of these autocorrelation functions

Model system for the management of nitrogen leaching at the scale of river basins and regions

In the framework of the EU-project RANR (Regional analysis of subsurface nitrogen retention and its impact on the nitrogen export from land to sea) a model system was developed to estimate groundwater-borne nitrogen inputs into river systems. The core of this model system is composed of a soil nitrogen leaching model (SOIL-N) and a groundwater residence time/denitrification model (WEKU). The application of the model system was carried out for the study catchment areas of the Uecker basin (ca. 2400 km(2), Germany) and the Gjern basin (ca. 200 km(2), Denmark). For both catchment areas, the modelled average nitrogen loads leached into the groundwater were about 40 kg N/ha a, while the remaining groundwater-borne nitrogen intake to rivers was quantified to an average of about 2 kg/ha a. The comparision with observed groundwater-borne riverine nitrogen loads showed a very good agreement, proofing the key role nitrogen retention in groundwater plays in the two catchment areas. With regard to the generalisation and transfer of the SOIL-N/WEKU model concept we assume that the model can be applicated in catchment areas in the European Pleistocene Lowland, which ranges from the Netherlands in the west to the Baltic States and the Ukraine in the east

NITREX project - Gårdsjøn. Status report for 1988-1990

At the NITREX site at Gårdsjøn, Sweden, nitrogen deposition will be experimentally increased to an entire forested catchment to study the potential for nitrogen saturation. Investigations include regular sampling of precipitation, thoughfall and runoff and compilation of input-output beugets. Short-term experiments of toxicity of the runoff water to fish are also underway. Studies of vegetation and soils are centered around three vegetation types characteristic of the catchments. Plots have been selected on the basis of soil and vegetation maps of the three catchments. Regular measurements include (1) volume and chemical composition of soil solution, (2) soil temperature, (3) chemical composition of needles, (4) amount and chemical composition of litterfall, and (5) soil moisture. In addition studies of mineralization, fine roots, and mycorrhiza are being conducted. Nitrogen addition will begin in April 1991. The NITREX data from Gårdsjøn will be combined with similar data from the other NITREX sites throughout Europe

Nitrex project - Gårdsjöen, Status report for 1990-91

At the NITREX site at Gårdsjön, Sweden, ambient nitrogen deposition of 90 meg m² yr 1 will be experimentally increased by 286 meg m² yr 1 to an entire forested catchment G2 to study the potential for nitrogen saturation. Investigations include mearsurements of catchment inputs and outputs, as well as studies of vegetation, soil, mycorrhiza, fine roots and fish response. Results from the pre-treatment period 1990-91 show acidic runoff and soil solution with high concentrations of inorganic aluminium. Concentrations of nitrate and ammonium are very low, indicating no nitrogen satuation. The trees are slightly-to-moderately defoliated, and the needles are discolored. The nutrient contents of needles indicate that no elements are in the deficiency or the toxin range. The mycorrhiza of the root mat at the forest floor are generally 100 % alive and healthy. At catchment G2 nitrogen addition began April 1991.NMF/NAVF, SN