Abstract. The application of the hydrological process-oriented model J2000 (J2K) is part of a cooperation project between the Thuringian Environmental Agency (Thüringer Landesanstalt für Umwelt und Geologie – TLUG) and the Department of Geoinformatics of the Friedrich-Schiller-University Jena focussing on the implementation of the EU water framework directive (WFD). In the first project phase J2K was parametrised and calibrated for a mesoscale catchment to quantify if it can be used as hydrological part of a multi-objective tool-box needed for the implementation of the WFD. The main objectives for that pilot study were: The development and application of a suitable distribution concept which provide the spatial data basis for various tasks and which reflects the specific physiogeographical variability and heterogeneity of river basins adequately. This distribution concept should consider the following constraints: The absolute number of spatial entities, which forms the basis for any distributive modelling should be as small as possible, but the spatial distributed factors, which controls quantitative and qualitative hydrological processes should not be generalised to much. The distribution concept of hydrological response units HRUs (Flügel, 1995) was selected and enhanced by a topological routing scheme (Staudenrausch, 2001) for the simulation of lateral flow processes. J2K should be calibrated for one subbasin of the pilot watershed only. Then the parameter set should be used on the other subbasins (referred as transfer basins) to investigate and quantify the transferability of a calibrated model and potential spatial dependencies of its parameter set. In addition, potential structural problems in the process description should be identified by the transfer to basins which show a different process dominance as the one which was used for calibration does. Model calibration and selection of efficiency criteria for the quantification of the model quality should be based on a comprehensive sensitivity and uncertainty analysis (Bäse, 2005) and multi-response validations with independent data sets (Krause and Flügel, 2005) carried out in advance in the headwater part of the calibration basin. To obtain good results in the transfer basins the calibrated parameter set could be adjusted slightly. This step was considered as necessary because of specific constraints which were not of significant importance in the calibration basin. This readjustment should be carried out on parameters which show a sensitive reaction on the identified differences in the environmental setup. Potential scaling problems of the process description, distribution concept or model structure should be identified by the comparison of the modelling results obtained in a small headwater region of the calibration basin with observed streamflow to find out if the selected efficiency measures show a significant change.

Abstract. The scientific sound definition of measures to achieve the goals of the EU water framework directive (WFD) acquires spatially distributed analyses of the water and substance dynamics in meso- to macro-scale catchments. For this purpose, modelling tools or systems are needed which are robust and fast enough to be applied on such scales, but which are also able to simulate the impact of changes on single fields or small areas of a specific land use in the catchment. To face these challenges, we combined the fully-distributed hydrological model J2000 with the nitrogen transport routines of the Soil Water Assessment Tool SWAT model, which are normally applied in a semi-distributive approach. With this combination, we could extend the quantitative focus of J2000 with qualitative processes and could overcome the semi-distributed limitation of SWAT. For the implementation and combination of the components, we used the Jena Adaptable Modelling System JAMS (Kralisch and Krause, 2006) which helped tremendously in the relatively rapid and easy development of the new resultant model J2000-S (J2000-Substance). The modelling system was applied in the upper Gera watershed, located in Thuringia, Germany. The catchment has an area of 844 km2 and includes three of the typical landscape forms of Thuringia. The application showed, that the new modelling system was able to reproduce the daily hydrological as well as the nitrogen dynamics with a sufficient quality. The paper will describe the results of the new model and compare them with the results obtained with the original semi-distributed application of SWAT.

The aim of this paper is to assess the hydrological system of the Okavango headwater tributaries, namely the Cuito and Cubango subcatchments, and the flow characteristics of the Okavango after their confluence at Mukwe. This assessment was applied at several gauging stations in the Cubango River reaching from the station Chinhama in Angola down to the station Rundu in Namibia and for two gauging stations (Cuito Cuanavale and Dirico) in the Cuito River system. Identifying hydrological flow characteristics by analysing time series discharge data in terms of frequency, low and peak flow events, and upstream downstream linkages in the mentioned tributaries was supported by the analysis of spatially distributed climate time series and basin characteristics. The analysis of the existing datasets in this data scarce region revealed that the headwater catchments are different in runoff generation, river bed morphology, and storage capacities. The amount of delivered discharge from the Cubango is more varied in amplitude and frequency compared to the more base flow dominated Cuito discharge. Analysing spatial datasets indicated significant differences in natural landscape system features leading to different runoff generation, from fast discharge hydrographs (Cubango) to base flow driven flow dynamics (Cuito). Compiled data as well as assessed hydrological dynamics will allow for the follow-up application of process based J2000 and J2000-g hydrological models for water balance assessment and river basin rainfall-runoff modelling.Keywords: Cubango River; Cuito River; flow duration curves; hydrological assessment; Okavango catchment; upstream-downstream analysis.A avaliação da dinâmica hidrológica no alto da bacia do rio Okavango Resumo: O objetivo deste trabalho é avaliar o sistema hidrológico dos afluentes da cabeceira do Okavango, ou seja, as subbacias Cuito e Cubango, e as características do fluxo do Okavango após sua confluência no Mukwe. Essa avaliação foi aplicada em várias estações de medição no rio Cubango, atingindo desde a estação Chinhama em Angola, descendo até a estação Rundu na Namíbia e duas estações de medição no sistema do rio Cuito (Cuito Cuanavale e Dirico). A identificação das características do fluxo hidrológico por meio da análise de dados de descarga de séries temporais, em termos de frequência, eventos de fluxos baixos e de picos, e as ligações a jusante e a montante nos afluentes mencionados, foi apoiada pela análise das séries temporais climáticas espacialmente distribuídas e das caracteristicas da bacia. A análise dos conjuntos de dados existentes, nessa região escassa de dados, revelou que as cabeceiras das bacias são diferentes na geração de escoamento, na morfologia do leito do rio e na capacidade de armazenamento. A quantidade de descarga distribuida pela Cubango é mais variada em amplitude e freqüência em comparação com a descarga de maior fluxo de base dominada de Cuito. A análise do conjunto de dados espaciais indicou diferenças significativas nas características do sistema de p...

Proper management of valuable land resources is of paramount importance especially in regions affected by natural hazards. The sustainable development of land resources depends on the understanding of the processes and dynamics active within the landscape. In Southern African countries water shortage and water quality issues related to soil erosion are a major problem affecting the population in rural and urban areas. Consequently, during the last decade increasing attention has been focussed especially on such issues, and an increasing number of integrated hydrological and erosion studies, including the development and application of respective integrated regionalization concepts, is reflecting this development. The present study deals with the regionalization of spatially distributed hydrological related erosion processes in the catchments of the Mkomazi river (KwaZulu-Natal, South Africa) and the Mbuluzi-river (Kingdom of Swaziland). It was carried out within the framework of an interdisciplinary EU-funded project developing an Integrated Water Resources Management System (IWRMS) in semiarid catchments of Southern Africa. Within this project the concept of “Response Units (RUs)” was applied and adapted as Erosion Response Units (ERUs) to regionalize the distribution of hydrologically induced soil erosion in space and time. ERUs are landscape model entities identifying relative homogeneous hydrological related erosion processes, thus providing a spatially distributed model structure for regionalization. The examples from Southern Africa presented in this paper discuss the methods used to delineate such Response Units integrating remote sensing and GIS techniques.