Improved SWAT Model Performance with Time-Dynamic Voronoi Tessellation of Climatic Input Data in Southern Africa

This scientific article, published in JAWRA in February 2012, presents a new method to prepare climatic input data for hydrological models. The method significantly improves disharge simulations. I developed it together with colleagues at Eawag, ETH Zurich, and AWRI.



In this study, we compared two approaches to obtain climatic time series for the Soil and Water Assessment Tool (SWAT), namely the conventional centroid method and time-dynamic Voronoi tessellation, and assessed the performance of SWAT in simulating discharge and smallholder maize yields in Southern Africa. Climatic time series were estimated with each method. The Voronoi method utilized all available precipitation and temperature data, but the centroid method used only 14.5 and 82.5%, respectively. After centroid processing, sub-basin time series were on average 42 and 63% incomplete, respectively. After Voronoi processing, all time series were complete. SWAT was fed with each climate dataset. Each model setup was independently calibrated and validated against discharge and maize yield. Similar model performance was obtained with both methods for yield. The root mean squared error during calibration was 0.26 and 0.27 t ha-1 for the centroid and Voronoi methods, respectively (p-value: 0.80). However, daily discharge simulations improved significantly with the Voronoi method. The coefficient of determination increased from 0.24 to 0.39 in the calibration period (p-value: 9.6×10-13) and from 0.41 to 0.48 in the validation period (p-value: 3.1×10-3). The Voronoi method improved the simulation of the river flow regime. The largest improvements were obtained in data scarce situations, at high spatial and temporal resolution, and where the centroid method performed the worst.


Andersson, Jafet C.M., Zehnder, Alexander J.B., Wehrli, Bernhard, and Yang, Hong (2012). Improved SWAT Model Performance with Time-Dynamic Voronoi Tessellation of Climatic Input Data in Southern Africa. Journal of the American Water Resources Association, Paper No. JAWRA-10-0200-P,pp. 1-14. doi: 10.1111 ⁄ j.1752-1688.2011.00627.x


You can obtain a copy of the article from JAWRA or by contacting me directly.