A new modeling and calibration approach considering time variant recharge areas in karst systems
Abstract
In karst systems, various types of porosity create a strong heterogeneity of water flow and storage mechanisms. For a sustainable present and future water management predictive modeling is necessary, which has to be done by approaches that consider the particularities of karst systems. In our study we present a new type of hydrological model that considers the variability of karst system properties and a new calibration strategy that focuses on the problem of variable recharge areas typical in karst systems. Defining objective functions that consider hydrodynamic and hydrochemical information we first determine model parameters that are responsible for hydrodynamic response, without taking into account the recharge. Then, the recharge area is determined separately for individual hydrological years and entire time period by calibrating the model to fulfill the annual water balance. This stepwise calibration is done simultaneously for the new model and -for comparison for a simple reservoir model. The new approach was applied to a karst system at Southern Spain where we can show that hydrochemical information is crucial to find the most plausible set of parameters for both models. Considering different hydrological years we find that the recharge area is changing significantly (from 28 to 53 km2) among the years for the reservoir model, which indicates that there is a variable recharge area. The newly developed model shows much less variability of the recharge area at individual hydrological years and provides acceptable results for the whole time period. This is due to the consideration of variable soil and epikarst depths: they produce a time-variant "effective" recharge area dependent on rainfall amounts and soil and epikarst saturation. Considering the hydrogeological functioning of the area, this process can most probably be attributed to allogenic recharge. Hence, our karst-specific calibration approach identifies a variable recharge area and the new model is able to reproduce this process. Therefore we claim that the new model provides a more realistic system representation, which can be of high significance when the model is used beyond the conditions it was calibrated, e.g. for land-use or climate change scenarios.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.H11F1258L
- Keywords:
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- 1829 HYDROLOGY / Groundwater hydrology;
- 1846 HYDROLOGY / Model calibration;
- 1847 HYDROLOGY / Modeling