Description
The forecasted effects of climate change for the region of Saxony place new demands on water management. The KLiWES project researches these changes with respect to Saxony's water catchment area. The programme aims to evaluate the different catchments with respect to their levels of sensitivity to these changes. The complex research will result in recommendations for new region-specific water management policies. The research involves the analysis of current and scientifically-based water balance data. Computer and mathematically based models are needed which satifactorily reflect the above and below ground process components, including their inter reaction with one another. This is essential for reliable, hydrologically sound water balance data.
The programme builds on the results of former less ambitious projects in which suitable water balance models were designed and tested. One of the problems encountered was that model comparisons for specific reference areas often resulted in widely varying results. These aberrations are a consequence of differing or unsatifactory methodical approaches, dissimilar data input, incompatible corrective procedures as well as individual variations in model practice.
The results of all the former research projects were amalgamated into one complex model concept. thereby minimising the risk of basing further research on uncertain, shakey data. The concept consists of 4 sections (SCHWARZE et al. 2008):
Concept of KliWES
- Evaluation of all the recorded hydrological and meteorological data (i.e since records exist) in order to evaluate the actual current catchment water balances
The DIFGA model to be used for column A will scientifically evaluate the data records routinely taken over many years and will suitably adapt the information for use in column B. Column B serves as a basis for a parameter model of the ground water module and will serve as a back up for the water balance model in column B. The DIFGA model is used to calculate the flow component related catchment specific water balance and provides a result which is independent of column B and which is able to be used for the calibration and validation of column B results. However, column B water balance calculations are significant and are not transferable due to the fact that necessary areal input date is lacking and this endangers the prognostic ability as far as an analysis of the actual situation is concerned. - A combined soil water and ground water balance model to form a water balance model for scenario studies for saxony-wide, area specific hydrological calculations.
Column B is the most important factor in the concept. As seen in the figure above, it consists of a soil water balance model and a ground water balance model. By using model approaches which describe the various steps of the procedure, the robustness and prognostic ability of the water balance data will be assured. A multitude of models are available for a description of the soil water balance. A multi step comparison test using various models at different scales will serve to decide on the model to be used throughout Saxony. Amongst the models under consideration are e.g AKWA-M, ArcEGMO, Mike-She and WaSiM-ETH. Besides the use of a Lysimeter, the models will be applied in micro catchments with gauges and at catchment scale and an areal calibration concept will be established. Concomitantly, this will result in the creation of physically interpreted and validated parameter models. These models will be applied to Lysimeters and within micro catchments wil the objective of testing their suitability. The application on Lysimeters serves to evaluate the models descriptive ability pariticularly in the soil water balance and phenology modules of the varying models. The ability of the respective models to deal with differing scenarios can thus be estimated. It is only here that relevant observation values are available for a comparison of simulated water balance components with actually measured parameters. On the threshold of micro catchments with gauges - as a back-up support for the Lysimeter readings - lateral discharge components can also be brought into consideration. For these micro catchments only data for the discharge is available for an evaluation of model results. As this is the case, the data can only be used to complement the Lysimeter calculations and should not be allowed to substitute them. Appropriate test areas will be chosen on the basis of the influences of the respective land use / coverage (e.g. field, forest...) and also as to the geological compatibility (solid / loose stone). The last step in the procedure sees the introduction of the model at catchment scale. In order to be able to better evaluate the proposed later application throughout the whole of Saxony. Parallel to this, a methodology will be devised for complete areal application, which will facilitate an - as far as possible - automatic calibration process. It is proposed to extract the physically based parameters from the calibration procedure. The establishing of parameter models has to rely on the availablity of appropriate saxony-wide data records. Concerning the suitability tests for the available parameter models, emphasis should be placed on the model's qualities with respect to interpretability and its possibilities for validation. For knowledge of the current actual condition, a validation of the calibrated models is only possible by a comparison with discharge observation data, with records of source discharge measurements and with the ground water levels. Due to a lack of observation data, a direct validation for forecasting purposes is unrealistic. For this reason, the results can only be looked at in terms of plausibility. Ideally, further possibilities for comparing the states of other actual conditions with common parameters should be examined. - Straightforward calculation without calibration for a multi-area evaluation of Saxony's complete water balance. Simplified evaluation of scenarios during the application phase with access to GIS based research data.
Due to the complexity of column A and column B, these cannot be used online. For this reason all analyses and calculations are stored in an updatable data bank. In order to treat problems which need to be dealt with online, a third column - column C - was introduced to the concept. This is because all possible future user-based questions will not be able to be adequately answered by column B nor stored in the data bank. Column C represents a relatively simplified approach for the calculation of a water balance and can be applied quickly and reliably, without renewed calibration. - Information - research and library module
The concept is to receive additional back-up in the form of an information and library module, which will offer additional research possibilities and serve to assimilate further relevant and useful information.
The results of the project are to appear in a scientific journal 'Waterbalance and climate change in Saxony' ("Wasserhaushalt und Klimawandel in Sachsen") expected to appear during 2012 in the internet.