FutureWater is evaluating the possibilities to regionalize the Penman-Monteith reference evapotranspiration in the Netherlands. The current standard in the Netherlands is Makkink. However, the international standard is Penman-Monteith. FutureWater studies which measured variables are required for the use of Penman-Monteith at Dutch weather-related organizations. Furthermore, FutureWater investigates the possible spatial interpolation methods.
More details, including the presentation [in dutch] can be found here.