Simulation of hydrological balance on experimental catchments Všeminka and Dřevnice in the extreme periods 1992 and 1997

Hydrological research on the Všeminka and Dřevnice experimental catchments has been carried out for almost ten years. Earlier analyses on these catchments have provided many partial results in the assessment of land use on water regime and also some analysis of extreme hydrological event conditions. This paper gives attention to identification of extreme hydrological periods (i.e floods and droughts) and to the simulation of events when these catchments are in that time impacted by the torrential rainfall of design character with the periodicity P = 0.01 (N = 100 years). This is the core of the paper focusing on the analyses of extreme summer periods in 1992 (dry season) and 1997 (flood season). These 50-day periods were first reconstructed in their real existing situations with a particular reference to compute the main components of water balance. This reconstruction was implemented by the WBCM model using the parameter values derived from the optimalisation process of some annual vegetation periods in the past. These parameter values were used to simulate both extreme situations when the design rainfall impacted the experimental catchments. In the dry period of 1992, the design rainfall of 100-years caused the direct runoff increase on Všeminka for 13%, on Dřevnice for 32%. In the flood period of 1997 this increment of direct runoff should achieve 52% on Všeminka and even 93% of the existing situation on the Dřevnice catchment. The differences between two experimental catchments are caused by the different retention capacities of their active zones.