Impacts of rainfall variability on river discharges characteristics : A Case Study in Chenyulan Watershed, Taiwan, China

In this study, the variations of rainfall and river discharges were analyzed in the Chenyulan watershed in Nantou County, central Taiwan. The hydrological data, including rainfall, daily discharges and yearly maximum instantaneous discharge, were collected from the Neimaopu hydrology station for the period from 1972 to 2022, covering approximately 50 years. According to the data analysis, when the rainfall exceeds the average, the river discharges in the Chenyoulan catchment increases, with larger rainfall events leading to more significant changes. Upon comparing the long-term data, it was found that the maximum instantaneous discharge occurred on August 1, 1996, during the Herb Typhoon. Though this event did not coincide with the historical maximum for total rainfall, rainfall intensity or average rainfall intensity, it resulted in the maximum instantaneous discharge.

 

 All of the rainfall events, daily average discharge and yearly maximum instantaneous discharge are preliminarily analyzed as follows: 1. Rainfall in the catchment shows a positive correlation with river discharge; 2. The increase in rainfall characteristics in the catchment and the increase in discharge are not linearly related; 3. The non-linear reasons for the relationship between rainfall and maximum instantaneous discharge are preliminarily summarized as being related to soil conditions, different rainfall intensity locations and the runoff coefficients of various catchment units; 4. This study will subsequently estimate the average runoff coefficient of the catchment based on the relationship between individual rainfall and discharge, and conclude rational formula.