Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 3 2 1999 10.5194/hess-3-305-1999 http://www.hydrol-earth-syst-sci.net/3/305/1999/ http://www.hydrol-earth-syst-sci.net/3/305/1999/hess-3-305-1999.html http://www.hydrol-earth-syst-sci.net/3/305/1999/hess-3-305-1999.pdf 305 307 0000-00-00 Hydrograph Prediction - How much skill? M. Beran OB Research Services, The Croft, East Hagbourne, Didcot, Oxon OX11 9LS e-mail for corresponding author: max@oldboot.demon.co.uk The matching of estimated to observed hydrograph shape is central to much hydrological analysis. This research note quantifies built-in biases that tend to inflate goodness of fit indicies, biases that arise from the similarity of geometry between observed and estimated hydrographs.