Huaxia Yao

Studies and evaluations on interception processes during rainfall based on a tank model

Abstract Some analyses are carried out with regard to canopy interception processes during rainfall events based on a tank model. A hypothesis, rainfall interception rate is proportional to the product of potential evaporation and rainfall intensity, is formed from past experimental data, and is applied to the data in this study. Computational equations are proposed to the interception rate and accumulative interception loss under constant rainfall intensity. Data from the Shirakawatani experimental forested catchment are used in order to examine the relationship between the interception rate and rainfall intensity, the ratio of the interception rate to rainfall intensity and potential evaporation, accumulative interception loss and the rainfall duration, and accumulative interception loss and accumulative rainfall. These regression relations show that interception processes are described by rainfall intensity and potential evaporation. An equation relating the aerodynamic resistance in the Penman–Monteith equation to rainfall intensity is proposed to explain the fact that the interception rate exceeds net radiation.

Modeling energy and water cycle in a forested headwater basin

Abstract A physical-mathematical model is proposed to describe hourly dynamics of water and heat transfers in a forested watershed which is conceptually divided into seven sub-compartments. Hourly, daily and annual water yield, evapotranspiration loss and canopy-soil temperatures are simulated. Inter-connecting energy budget and water balance processes are integrated by simultaneously solving related equations with a specific feedback-iteration method. Emphasis is placed on interaction of transpiration and soil water status, on nonlinear and nonuniform overland flow, and on the controlling function of each storage on water fluxes. The model is calibrated by using the SIMPLEX optimization, at the Shirakawatani catchment in Western Japan, with hydrometeorology data for 2 years. Simulated annual water yield deviated from the observations by only 1.65%, hourly, or daily runoff was statistically correlated to observed runoff at a level of 0.916 or 0.976, and flood process, leaf and soil temperature patterns were fitted well.