基于动态权重系数法的区域综合干旱指标研究

为揭示区域总体干旱程度及其变化特征,以长株潭地区为研究区,在标准化降水指数(SPI)、标准化水位指数(SZI)、标准化区域水资源短缺指数(SSDI)基础上,利用动态权重系数法构建区域干旱综合指标MIDI,结合历史受旱面积率、因旱减少供水量等旱情统计资料,对MIDI的适用性进行分析验证。以长株潭地区11个气象站、12个水文站近几十年实测资料为例,分别采用游程理论和Copula函数法识别干旱事件,并计算其发生频率,采用多尺度统计分析法,对区域综合干旱的演变特征进行分析。研究结果表明:SPI、SZI、SSDI对于不同水源、行业类型干旱评价各具优势,SPI、SSDI年干旱累积烈度与长株潭地区农业受旱面积率相关性相对较高;SZI年干旱累积烈度与城镇因旱减少供水量相关性较高,更适用于依靠地表径流为主要供水水源的城镇干旱地区评价。本研究提出的动态权重系数法,综合考虑了区域产业结构的年际变化、产业需水规律的季节性变化等因素,可反映不同阶段各单项指标干旱对于旱情的主导作用,适用于多种水源和产业类型的区域旱情综合评价;从月、季和年3种时间尺度,分析了长株潭地区MIDI综合干旱的变化特征,结果表明长株潭地区近20 a来极端干旱发生频次呈现波动增加趋势。

Regional Comprehensive Drought Index Based on Dynamic Weight Coefficient

To reveal the regional overall drought degree and its change characteristics, a regional drought comprehensive index (MIDI) was constructed by using the dynamic weight coefficient method based on the calculation results of standardized precipitation index (SPI), standardized runoff index (SZI) and standardized regional water shortage index (SSDI). The applicability of MIDI was analyzed and verified according to historical drought statistics such as drought-affected area rate and reduced water supply due to drought. With the measured data of eleven meteorological stations and twelve hydrological stations of Changsha-Zhuzhou-Xiangtan region in recent decades as input, the drought events were identified by using run length theory and Copula function method, and their occurrence frequency was calculated. Furthermore, the evolution characteristics of regional comprehensive drought were analyzed by using trend analysis method. Results manifested that SPI, SZI and MIDI index have their own advantages in drought evaluation for different water sources and industry types. The annual cumulative drought intensity of SPI and SSDI is highly correlated with the rate of drought-affected crop area; while the annual cumulative drought intensity of SZI is highly correlated with urban water supply reduction due to drought, hence is more suitable for assessing the drought of urban area which is relied on surface runoff as the major water supply source. The dynamic weight coefficient method proposed in this study reflects the leading role of single drought index in different stages by taking the interannual change of regional industrial structure and the seasonal change of industrial water demand regularities into consideration. It is suitable for the comprehensive regional drought evaluation of various water sources and industrial types. Last but not the least, the MIDI of Changsha-Zhuzhou-Xiangtan region was examined from monthly, seasonal and yearly scales, and results unveiled that the frequency of extreme drought in Changsha-Zhuzhou-Xiangtan region has been increasing fluctuatingly in the recent two decades.