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Incorporating elevation in rainfall interpolation in Tunisia using geostatistical methods
Authors:Haifa Feki  Mohamed Slimani  Christophe Cudennec
Institution:1. Laboratoire Sciences et Techniques des Eaux , Institut National Agronomique de Tunisie , 1082 , Tunis-Mahrajène , Tunisie haifa.fki@gmail.com;3. Département Génie Rural, Eaux et Forêts , Institut National Agronomique de Tunisie , 1082 , Tunis-Mahrajène , Tunisie;4. Agrocampus Ouest, UMR 1069 Sol Agro et Hydrosystème Spatialisation , F-35000 , Rennes , France;5. INRA, UMR 1069 Sol Agro et Hydrosystème Spatialisation , F-35000 , Rennes , France;6. Université Européenne de Bretagne , France
Abstract:Abstract

This paper compares the performance of three geostatistical algorithms, which integrate elevation as an auxiliary variable: kriging with external drift (KED); kriging combined with regression, called regression kriging (RK) or kriging after detrending; and co-kriging (CK). These three methods differ by the way by in which the secondary information is introduced into the prediction procedure. They are applied to improve the prediction of the monthly average rainfall observations measured at 106 climatic stations in Tunisia over an area of 164 150 km2 using the elevation as the auxiliary variable. The experimental sample semivariograms, residual semivariograms and cross-variograms are constructed and fitted to estimate the rainfall levels and the estimation variance at the nodes of a square grid of 20 km?×?20 km resolution and to develop corresponding contour maps. Contour diagrams for KED and RK were similar and exhibited a pattern corresponding more closely to local topographic features when (a) the network is sparse and (b) the rainfall–elevation correlation is poor, while CK showed a smooth zonal pattern. Smaller prediction variances are obtained for the RK algorithm. The cross-validation showed that the RMSE obtained for CK gave better results than for KED or RK.

Editor D. Koutsoyiannis; Associate editor C. Onof

Citation Feki, H., Slimani, M., and Cudennec, C., 2012. Incorporating elevation in rainfall interpolation in Tunisia using geostatistical methods. Hydrological Sciences Journal, 57 (7), 1294–1314.
Keywords:monthly average rainfall  semivariogram  cross-variogram  kriging with external drift  regression-kriging  co-kriging  Tunisia
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