Indoor imitation experimental study on driving factors of rainfall-runoff process

The driving actions are varied during the rain-fall-runoff process in a catchment. The impacts on therunoff process, caused by human activities or climatechange, can be attributed to two aspects: the charac-teristics of rainfall process and ground pad changes.To clarify their impacts on hydrological cycle is thefoundation of mechanism research of scientific hy-drology. So far, all of the research results, domestic andabroad, indicate that the advances on the understand-ing of hydrologica…

Indoor imitation experimental study on driving factors of rainfall-runoff process

The driving actions of rainfall-runoff process can be attributed to two aspects. The first is the influence of precipitation process, and the second is that of the ground pad. The re- search results of 179 indoor experiments conducted to imitate rainfall-runoff process indicate that both precipitation duration and intensity play important roles in affecting confluence lag time, which is obviously inconsistent with the traditional hypotheses. The nonlinear relationship is of great significance to the confluence curve especially when the precipitation duration is less than the total confluence time or the precipitation intensity is small. Therefore it can be concluded that the unit hydrograph (UH) can be applied to rainfall-runoff process imitation in the humid areas in the south China region. However, the UH application should be strictly modified in accordance with precipitation conditions in the arid and semiarid region of north China where the precipitation duration is short and the intensity is unstable. It will be hard to get ideal imitation results if the UH is applied blindly without considering specific conditions in the north China region. This also explains the unsatisfactory imitation results caused by using various hydrological models in the north China region. When the precipitation duration is short, and the watershed has not reached total watershed concentration, the characteristics of confluence change greatly, which reflects the actual situation in the north China region. Therefore necessary nonlinear corrections should be made when UH is applied. If the duration is longer than the total confluence time and the balance between pondage and discharge is stricken, the imitation research results will be applicable to both rainfall-runoff relation with longer duration in the south China region and the basic theoreti- cal research on runoff generation and concentration. On conditions of adequate rainfall, peak discharge is in linear relationship with intensity, but has nothing to do with the ground pad. There is a negative linear relationship between intensity and time to peak . The amount of pondage capacity in a catchment is in linear relationship with intensity and peak discharge, with obvious influence by the ground pad status and interception, and it has nothing to do with the position of interceptions.