基于分组赋权和改进内梅罗指数的赣江中下游整体水文改变度计算

Calculation of overall hydrologic alteration in middle and lower reaches of Ganjiang River based on grouping weighting and improved Nemerow index

针对传统整体水文改变度计算方法存在忽视IHA指标相关性和中低度改变指标影响的不足,探讨了一种基于分组赋权和改进内梅罗指数的整体水文改变度计算方法.该法将IHA水文指标划分为5组,利用CRITIC法分别对各组单独进行赋权,计算出各组综合水文改变度,然后采用改进的内梅罗指数法,进行整体水文改变度的评价.以赣江中下游为研究对象,依据峡江水文站和外洲水文站日径流资料,以1990年万安水库下闸蓄水作为赣江受到干扰的时间节点,运用三等级、改进的三等级法和本文方法比较分析其水文情势改变情况.研究结果表明:峡江水文站和外洲水文站均有27个指标达到中、低改变;三等级法计算出的峡江水文站整体改变度为69.16%,外洲水文站为69.43%,均属于高度改变;改进的三等级法评价结果是峡江水文站和外洲水文站均为中度改变;本文方法计算得到的两站整体改变度为49.36%与40.55%,均属于中度改变.进一步分析表明,本文方法综合考虑指标间的相关性,兼顾中、低度改变指标对评价结果的影响,计算出的整体水文改变度值具有一定客观合理性.

Aiming at the deficiency of the traditional overall hydrologic alteration method without considering the impact of the moderate and low alteration indexes and correlation among IHA,a new method based on the grouping weighting and improved Nemerow index is explored.The method divided IHA into 5 groups.Every group is weighted separately by the CRITIC method and calculated the comprehensive hydrologic alteration.And then,the improved Nemerow index method is used to evaluate the overall hydrologic alteration.Based on the daily runoff data of the Xiajiang and Waizhou hydrologic stations,the paper takes 1990 when the impoundment of the Wan’an reservoir started,as the disturbing time for the Ganjiang River,and compares and analyzes the alteration of hydrologic regime by using three-grade method,improved three-grade method and this method.The results show that 27 indexes reach the moderate or low alteration in the Xiajiang and Waizhou stations;the overall hydrologic alteration of the Xiajiang station is 69.16%,and that of the Waizhou station is 69.43%calculated by three-grade method,both of which belong to high alteration;the hydrologic alteration of the Xiajiang and Waizhou stations is moderate calculated by the improved three-grade method;the overall hydrologic alteration of the two stations are 49.36%and 40.55%respectively:both of which are moderately changed.The further analysis shows that the method in this paper takes into count the correlation among IHA and considers the impact of moderate and low alteration indexes on the evaluation,so that the results are reasonable and objective.