Assessment of Deterministic Model over Long Time Period Hydrological Simulation at Ungauged Mediterranean Catchment

In the Mediterranean area, because of the typical climate with hot dry summer and wet mild winter, the drought and flood hazards occur frequently. The Var catchment, located at the France Mediterranean area has nearly 3000 km2 control areas with elevation variation from sea level up to 3000 m. NICE as the second biggest city in this region, locates at the outlet of this basin which directly affected by the Var catchments. Clearly representing the long time period hydrological process in this catchment will produce an integrated view for the local managers to optimize the regional water resources. However, due to the complexity of the topography and geology in this area, it is difficult to manage series measurements over whole catchment. Hence to catch the hydrological process in this ungauged area, a distributed deterministic model MIKE SHE was applied to achieve our purposes. By collecting the daily rainfall data recorded by Meteo-France from 2008 to 2014, the hydrological model was built to represent the whole hydrological process including rainfall–runoff process and groundwater movement, etc. The model results showed that the rainfall–runoff response time of the catchment is less than one day which is close to the reality effected by the high slope distribution in this catchment. The model results showed that there is an obvious exchange process between the surface and groundwater in the catchment. At summer time when there is less rainfall for saturating the top soil, the channel discharge is relatively low. However, in the winter time after a short period rainfall saturated the soil; the following rainfall events always generate flood peaks. For the local managers, the extreme rainfall events after even a small rainfall in the winter time can produce significant flood damage and require fast social reactions. In conclusion, with the increase of the computer facilities, the distributed deterministic model gains more interest in the hydrological simulation. With the model characteristic which is based on the physical law, the parameters can be estimated by the model calibration. This case study in the Var catchment showed a succeed way to apply distributed deterministic model in an ungauged catchment to well represent the long time period hydrological process. The model strategy could be one of the useful references applying in other ungauged cases.