Assessing runoff in future climate conditions in Messara valley in Crete with a rainfall-runoff model


K. Voudouris, Laboratory of Engineering Geology and Hydrogeology, School of Geology, Aristotle University of Thessaloniki, Thessaloniki, Greece. E-mail:


The aim of this study is to develop a relationship between rainfall and surface water (runoff) in South Crete, Greece. This application was carried out on five sub-basins in the Messara valley, with a total surface of 1125 km2. Three factors were taken into account: the climate regime including precipitation and air temperature, the geological nature of the ground and the surface area of the basin. The development of the rainfall-discharge model consisted of three steps. Firstly, the actual evapotranspiration (Er) was computed. Secondly, the storage capacity of each hydrogeological unit in every catchment area was geologically estimated and, lastly, the rainfall-runoff model was developed using the water balance equation and the above mentioned relationship of Er. The amount of variance in runoff between the sub-basins explained by those three factors was 92%. Decreases in mean annual precipitation by 17 and 15% for east and west Messara, respectively, predicted by the regional climate model REMO resulted in even more drastic mean runoff reductions by 29 and 32% at the respective sides of the valley. Furthermore, the coefficient of variation of runoff increased by more than 15% in the east side of the valley but dropped by only 1.5% in the west. The proposed rainfall-discharge relationship is a useful tool for hydrological management and evaluation of water resources under the present-day and future climate conditions in Messara valley in Crete. Copyright © 2011 Royal Meteorological Society