黄河中游地区1977年7月4至6日、8月1至2日和4至6日发生三次大暴雨,简称“777”延安暴雨、“778”乌审旗暴雨和“778”平遥暴雨。为了解暴雨后小型库坝工程的情况,我们参加了对陕北延安、榆林,山西吕梁、忻县,甘肃庆阳等地区及内蒙准格尔旗等15个县(旗)的调查。三次暴雨中,乌审旗暴雨虽强度之大为以前所罕见,但主要雨区在沙漠区,只波及中游一小部分地区,对工程影响较小,故不在本文论述。仅就延安暴雨和平遥暴雨的调查结果整理如下。 Three heavy rainstorms occurred in the middle reaches of the Yellow River from July 4 to July 6, August 1 to August 2, and August 4 to 6, 1977, or “777” Yan’an heavy rain, “778” Wushen Banner heavy rain and “778” Pingyao heavy rain. In order to understand the situation of the small-scale reservoir and dam project after the rainstorm, we participated in the investigation of 15 counties (banners) in Yan’an, Yulin, Shanxi Luliang, Xinxian, Qingyang, Gansu, and Zhun Geer, Inner Mongolia. In the three torrential rainstorms, although the intensity of Wushen Banner torrential rain was rarely seen before, the main rain areas in the desert area and only a small part of the middle reaches have a small impact on the project and are not discussed in this article. The survey results of the heavy rain in Yenan and Pingyao were only compiled as follows.