The phreatic groundwater in the diluvial fan in front of the helan mountain is mainly recharged by precipitation and the lateral flow from the helan mountain ; the phreatic groundwater both in the diluvial fan of the qingtongxia gorge and in the fluvial plain is mainly recharged by the influent seepage of irrigation water from the yellow river 贺兰山洪积扇单一潜水主要接受山区侧向径流及大气降水补给；青铜峡洪积扇单一潜水及冲湖积平原上覆潜水，主要接受黄河灌溉水的入渗补给。
2.
The elementary idea of the reference units method can be described as follows : firstly , by the setting of double series of reference units , we can control the highest and lowest land quality class of each village or town ; secondly , the class of the arable land will be get through the contrast between the arable land with the reference unit which has been selected in the same area , the difference in quality is the key factor to classify the land . the results show , 87 . 6 % of the lands from i to iii distribute on alluvial and lacustrine plains , where the associated soils are mainly grey fulvo - aquic and calcareous concretions black ones . and 61 . 4 % of them from iv to vi distribute on slightly rolling parts with mainly yellow - cinnamon soil developed from the diluvial and slope deposits 分等结果表明：卧龙区等的耕地中，有87 . 6分布在冲积、湖积平原区，主要土壤类型是在河流冲积物上发育形成的灰潮土、在湖相沉积物上发育形成的砂姜黑土；等耕地中，有61 . 4分布在垄岗区，主要土壤类型是洪坡积物上发育形成的黄褐土：而、等耕地集中分布在丘陵区，主要土壤类型是残坡积物上发育形成的粗骨性黄褐土，等别结果分布总体上体现了不同地貌类型、土壤条件下耕地质量的差异。
