Satellite precipitation in southeastern South America: how do sampling errors impact high flow simulations?

Abstract

Satellite precipitation estimates are increasingly available at temporal and spatial scales of interest to hydrological applications and with the potential for improving flood forecasts in data-sparse regions. This study evaluates the effect of sampling error on simulated large flood events. Synthetic precipitation fields were generated in Monte Carlo fashion by perturbing observed precipitation fields with sampling errors based on 1, 2 and 6 h intervals. The variable infiltration capacity hydrological model was used to assess the impact of these errors on simulated high flow events in the Iguazu basin, a rain-dominated, subtropical basin in southeastern South America. Results showed that unbiased errors in daily error-corrupted precipitation fields introduced bias in the simulated hydrologic fluxes and states. The overall bias for error-corrupted daily streamflows was positive and its magnitude increased with larger sampling intervals. However, for high flow events, the bias was negative as a result of an increase in simulated infiltration and changes in precipitation variability. Errors in precipitation also affected the magnitude and volume of the peak events but did not change the first two statistical moments of the peaks indicating that non-linearities in the hydrological system preserve the statistical properties of high flows in the basin. Caution is needed when using satellite products for hydrological applications that require the estimation of large peaks and volumes.

Keywords:

• Flood forecasting
• peak flows
• satellite precipitation
• VIC model
• South America
• sampling errors

Acknowledgements

We would like to thank Hoori Ajami and Matej Durcik for their help with ArcGIS, and Julio Cañon-Barriga for his valuable comments. The Matlab code to compute the PGP distribution was kindly provided by Erick Rivera-Fernandez and Francina Dominguez at the University of Arizona. We are grateful to two anonymous reviewers whose careful review and helpful comments led to substantial improvements to this work.

Funding

This material is based upon work supported in part by NASA Precipitation Measurement Missions [grant number NNG05GA79G] to the University of Arizona and in part by SAHRA (Sustainability of semi-Arid Hydrology and Riparian Area) under STC Programme of the National Science Foundation [agreement No. EAR-9876800].