A physiographical study on the secular fluctuations and regional characteristics of rainfall-runoff processes

以两个流域为例，对比研究了近100年来降水、蒸散发和径流比等降雨径流特征组成部分的变化。自20世纪70年代上半叶以来，研究区年降水量呈减少趋势。另一方面，平滑的趋势曲线表明，年蒸散量在长期内增加，特别是自20世纪80年代以来。年降水量和潜在蒸散值之差的平滑长期变化与年降水量之差类似。在过去几十年中，每年的平均年径流量比率也呈现出下降的趋势。指出当前年降水频率-幅度分布的显著特征是水文极值的间隔在逐年减小，幅度在逐年增大。在1994年夏季气温升高的极端气象事件条件下，河流水质与正常年份的平均值相比发生了显著变化。由于温度高、流量小，最显著的特征是溶解氧浓度非常低，特别是在7、8月份。本研究确定的事实为全球变暖对降雨径流过程的可能后果提供了一个有意义的视角，也是评估未来气候变化对水生环境影响的有用基础数据。

Changes in the components of rainfall-runoff characteristics including precipitation, evapotranspiration, and runoff ratio over the last 100 years were comparatively investigated in two river basins as a case study. Annual precipitation in the study area has tended to decrease since the first half of the 1970s. On the other hand, the smooth trend curve indicates that annual evapotranspiration has increased over the long term, especially since the 1980s. Smoothed long-term changes in the difference between annual values of precipitation and potential evapotranspiration are analogous to those of annual precipitation. The average annual runoff ratio for each year has also shown a tendency to decrease during the last few decades. It is pointed out that the notable characteristics of current frequency-magnitude distributions in annual precipitation are both a reduction of intervals of hydrological extremes and an increase of range in each year. Under conditions of extreme meteorological events that increased air temperature in the summer of 1994, river water quality showed a remarkable change compared to its average value in a normal year. The most striking feature due to high temperature and small discharge was a very low value for the concentration of dissolved oxygen, especially in July and August. The facts identified in the present study provide a meaningful perspective of the possible consequences of global warming for rainfall-runoff processes, and are also useful basic data for evaluating the effects of future climate change on the aquatic environment.