Reconstruction of potential evaporation for water balance studies

A large number of environmental management decisions such as the remediatio n of a mine site require the best possible knowledge of the water balance o f the site or the catchment area. For precipitation a large number of obser vations exists and usually some data are available which are more or less r epresentative for the precipitation conditions in the catchment. However, t o close the water balance knowledge about evaporation is also required. Thi s is usually not available from observations. Also bulk formulas cannot be used to reconstruct evaporation for a sufficiently long time, since observa tions of the input variables are limited as well. In this article an approa ch is presented showing how local potential evaporation may be reconstructe d from other local and non-local atmospheric variables for which long-term observations are available. The method is demonstrated for the planned arti ficial lakes in the closed down mine sites in the Geiseltal (Germany) and a ims at the estimation of the probability distribution of the difference bet ween precipitation and evaporation for the surface water balance.