Jörg Helmschrot

Land use characterisation and change detection analysis for hydrological model parameterisation of large scale afforested areas using remote sensing

Abstract The impact of large scale land use changes such as afforestation on the hydrological system behaviour of river basins is of major interest to water resources managers. Particularly in semi-arid areas, where water is strongly limited, the continuous assessment and monitoring of the hydrological system components are necessary. Their analysis and prognostic hydrological modelling requires both the determination of updated land use patterns and an estimation of their spatial dynamics over time. In this study optical remote sensing data were used in order to provide such hydrological model input parameters at different scales. Therefore, Landsat TM data from 1995 to 1999 have been utilized for various scale depended land use maps within the semi-arid Umzimvubu catchment, South Africa. The classification results were compared due to the temporal changes as a consequence thereof the afforestation. Based on an complex accuracy estimation during all processing steps, significant changes of the land use patterns could be quantified. In addition, the Leaf Area Index (LAI) distribution has been calculated for the Mooi river subcatchment based on the transformation of the normalized difference vegetation index derived from Landsat TM data to LAI utilizing an empiric equation.

An Information System for Integrated Land and Water Resources Management in the Kara River Basin ( Togo and Benin )

A prerequisite for integrated land and water resources management (ILWRM) is a holistic river basin assessment. The latter requires information and data from different scientific disciplines but also appropriate data management systems to store and manage historical and real time data, set up protocols that facilitate data and information access and sharing among different stakeholders, and triggering further collaboration among different institutions in support of watershed-based assessment, management and planning. In West Africa in general and especially in the transboundary Volta River basin where different environmental data are collected and managed by different agencies in different countries and also where data access and dissemination are very challenging and difficult tasks, comprehensive river basin information systems are required. This paper presents the Oti River Basin Information System (OtiRBIS), a web-based data storage, management and analysis platform that addresses these needs and facilitates ILWRM implementation in the Kara river basin.

Hydrological system analysis and modelling of the Kara River basin (West Africa) using a lumped metric conceptual model

ABSTRACT This paper discusses the analysis and modelling of the hydrological system of the basin of the Kara River, a transboundary river in Togo and Benin, as a necessary step towards sustainable water resources management. The methodological approach integrates the use of discharge parameters, flow duration curves and the lumped conceptual model IHACRES. A Sobol sensitivity analysis is performed and the model is calibrated by applying the shuffled complex evolution algorithm. Results show that discharge generation in three nested catchments of the basin is affected by landscape physical characteristics. The IHACRES model adequately simulates the rainfall–runoff dynamics in the basin with a mean modified Nash-Sutcliffe efficiency measure of 0.6. Modelling results indicate that parameters controlling rainfall transformation to effective rainfall are more sensitive than those routing the streamflow. This study provides insights into understanding the catchment’s hydrological system. Nevertheless, further investigations are required to better understand detailed runoff generation processes. EDITOR M.C. Acreman; ASSOCIATE EDITOR N Verhoest

A Comparative Analysis Of The PRMS And J2000Hydrological Models Applied To The SandspruitCatchment (Western Cape, South Africa)

The applicability of distributed hydrological models to the semi-arid conditions in the Western Cape was investigated through the application of PRMS and J2000 in the Sandspruit Catchment. The Sandspruit is an annual river, with the catchment receiving 300-400 mm/a of rainfall. The catchment exhibits shallow soils, with the dominant land uses being cultivated lands and pastures. To optimise the parameterisation of the models, 21 boreholes were drilled throughout the catchment for data collection and to get a better conceptual understanding of the catchment’s hydrologic conditions. Field evidence suggests that subsurface flow is the dominant contributor of streamflow and thus the models were calibrated accordingly. The models were run for a 20 year period. Both models were able to match the timing of seasonal hydrograph responses, however they were not able to match annual discharge volumes. Annual discharge was overestimated in certain cases and underestimated in others. Both models exhibited daily Nash-Sutcliffe Efficiencies of below 0.4. As the models were parameterised and calibrated manually, the feasibility of using automatic techniques needs to be investigated.