Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 11 1 2007 10.5194/hess-11-408-2007 http://www.hydrol-earth-syst-sci.net/11/408/2007/ http://www.hydrol-earth-syst-sci.net/11/408/2007/hess-11-408-2007.html http://www.hydrol-earth-syst-sci.net/11/408/2007/hess-11-408-2007.pdf 408 414 2007-01-17 Hydrological prediction in a non-stationary world R. T. Clarke The paper discusses evidence that common assumptions in the analysis of hydrological time series (homogeneous variability in random fluctuations about a constant mean value) may not be appropriate for some South American drainage basins. Relatively rapid changes have occurred, and are occurring, as a consequence of replacing mature forest by short crops and urban development. Some research claims to have detected non-linear trends in streamflow in rivers draining the south-eastern part of the sub-continent, together with decadal fluctuations and interannual peaks at ENSO timescales. The paper discusses the implications of such changes for hydrological practices now in widespread and largely unquestioned use.