Rainfall generator for the Meuse basin: Extension of the base period with the years 1999-2008

In KNMI publication 196-III a multi-site weather generator for the French and Belgian parts of the Meuse basin was developed. Daily precipitation and temperature are generated by resampling from the observed daily precipitation and temperature for the period 1930-1998 (or 1961-1998) using a nearest-neighbour technique. This weather generator forms part of a new methodology to estimate the design discharge for flood protection works in the Netherlands.

In this report the extension of the base period for resampling up to 2008 is discussed. The homogeneity of the long precipitation series that drive the resampling procedure was tested in the same way as for the old base periods. This resulted in a small number of inhomogeneities near the end of the old base periods.

A new 20 000-year simulation was conducted using the extended base period 1930-2008. The precipitation series driving this simulation were corrected for inhomogeneities. The resulting distributions of the 10-day winter precipitation maxima were compared with those of an earlier 20 000-year simulation, based on the 1930-1998 data (the reference ‘Ref’ simulation in KNMI publication 196-IV). The differences between the extreme-value distributions for both simulations turned out
to be small.

The actions necessary to apply the weather generator on a routine basis for the estimation of the design discharge are outlined. Bottlenecks are the provision of climate data from foreign countries, handling of missing data and inhomogeneities,and the determination of area-average precipitation over the subbasins. A point of
concern is the maintenance of knowledge on resampling procedures and climate data of the Meuse basin.