渭河流域气象及水文旱涝演变规律分析

Analysis on evolution law of meteorological and hydrological drought and wetting

降水是径流的基本来源,分析极端旱涝条件下降水与径流之间演变规律的异步性,可有效表征径流丰枯变化对人类活动的响应。基于渭河流域降水、径流资料,采用泰森多边形法计算渭河流域面降水量及12个月标准化降水指数（SPI12）,对比典型频率下SPI12的空间分布特征及其对径流系数的影响;采用经验正交函数和时间序列分析法挖掘SPI12和年径流量的演变规律,对比演变规律的同步及异步变化特征。结果表明：在25%、50%、75%频率下,流域面降水量分别为582.5 mm、518.6 mm、467.5 mm。SPI12第一主成分减少趋势显著,自1991年7月开始突变,于1962-09（1962年9月,下同）-1969-07-1983-02-1985-08-1991-07-1999-12呈现湿润~正常~湿润~正常~干旱状态。渭河年径流量呈显著减少趋势,自1989年开始突变,且分别于1950-1968和1982-1993年经历湿润和正常阶段,于1970-1974、1976-1980、1994-2007年经历干旱阶段。以流域内大规模水利、水土保持措施及城市化等为代表的人类活动使流域年径流量较SPI12第一主成分突变年份提前,使二者于1970-1996年间旱涝类型不匹配,年径流量相对SPI12第一主成分呈现旱化趋势。

Runoff basically origins from precipitation.The differences of the evolution law between them could effectively reveal the effect of human activities on drought and wetting.This paper based on hydrological and meteorological data,the watershed precipitation is calculated by Thiessen Polygon method and the 12 month standardized precipitation index（SPI12） is also acquired.Furthermore,the spatial distribution of SPI12 is presented by different typical frequencies and its effects on runoff coefficient have also been detected.Moreover,the evolution law of SPI12 and runoff is analyzed by EOF and time series analysis method,the synchronization and induction of which is also detected.The results shows that the watershed precipitation corresponding to 25%,50% and 75% frequencies are respectively 582.5 mm,518.6 mm and 467.5mm.And the 1st principal component of SPI12 decrease significantly and appears wet-normal-wetnormal-drought during 1962.9～1969.7～1983.2～1985.8～1991.7～1999.12,the change point of which is 1991.7.The runoff in Wei River decreases significantly and abruptly changes in 1989a.And the runoff presents wet in 1950—1968a,normal in 1995—2002a and drought in 1970—1974,1976—1980,1994—2007a.The human activities,including water conservancy project,water and soil conservation measurement and urbanization,make the change point of runoff earlier than that of SPI12,the runoff more dry than the 1st principal component of SPI12,and lead to the mismatch of wet,normal and drought types between runoff and SPI12 during 1970—1996a.