江淮下游降水特征及其对水位的影响研究——以里下河腹部地区为例

Precipitation Variations and Its Impact on Water Level in the Lower Reaches of Jianghuai Basin:A Case Study in the Inner Lixiahe Region

采用降水集中度、等级分析及小波相干等方法,探讨了江淮下游里下河腹部地区1957—2006年间降水、水位的等级特征及两者关系。结果表明:①年降水量的集中期与集中度皆为减小趋势,两者在1980年前后由同相位转为反相位相关。②汛期高等级降水的日数和贡献率皆以1980年代最高。不同等级的降水日数皆为减少趋势,但高等级降水的贡献率在大洪涝年中异常偏高,表明降水强度加强。③低、高等级水位日数皆为减少趋势,但低、高等级水位的贡献率分别呈增加、减少趋势,而中等级水位的日数与贡献率都显著增加。较之降水日数,降水贡献率对水位等级变化更具决定性影响。④高等级降水与水位在日数上呈显著的同相位正相关,但低等级相反,而中等级为较弱正相关,且等级降水总量与相应水位贡献率的相位关系亦具类似特征。高、低等级降水与水位的贡献率皆为显著同相位正相关,但在中等级上,其相位特征较弱。

Methods of precipitation concentration period and precipitation concentration degree analysis, classification analysis and wavelet coherence analysis are applied to explore the variations and relationship between precipitation and water level from 1957 to 2006 in the inner Lixiahe region, an area located in the lower reaches of Jianghuai basin. Results show that decreasing trends can be detected both in precipitation concentration period and precipitation concentration degree for the annual precipitation, it experienced an in-phase to anti-phase switch in 1980. Maximum days and contribution rate of higher grades of precipitation appeared in 1980s. Decreasing trend can be observed in the days of lower, middle and higher precipitation grades. However, precipitation contribution rate tends to be significantly higher in flooding years implying an increasing in precipitation intensity. Decreasing trend can be observed for the lower and the higher grades of water level days, but that it turns out to be increasing and decreasing trend for the lower and higher grades of water level contribution rate respectively. However, a significant increasing tendency can be identified for the middle grades of water level days and contribution rate with an implication that there might be an enhanced accumulation impact of middle precipitation grade on water level, this could be resulted from the negative hydrological effect of enhanced human activities. Precipitation contribution rate has more important impact on water level change compared to the precipitation days. A positive correlation can be examined between higher precipitation grade and water level days, while negative and positive correlation can be detected between lower and middle grade days of precipitation and water level respectively, and a similar phase relation can be found in grade total precipitation and contribution rate of water level. Furthermore, higher, lower and middle grade total precipitation exhibits an in-phase, anti-phase and weak phase relation with the corresponding water level respectively.