论关中盆地古代城市选址与渭河水文和河道变迁的关系

On the Connection Between the Location of the Ancient Towns in the Guanzhong Plains and the Alterations of the Weihe’s Hydrology and Waterway

关中盆地古代城市的选址、建设、迁移与渭河水文和河道变迁密切相关,经历了城市生活用水从依赖渭河水源到改用支流水源,交通以渭河航运为主到依赖漕渠再到缺乏航运条件,城市从渭河北岸迁移到渭河南岸,从靠近渭河到远离渭河的变化过程。城市靠近渭河是为了方便生活用水和航运。城址选在渭河北岸可取山水之阳,但北岸支流少,泥沙多,供水条件不如南岸,且北岸平原面积狭小,渭河的北迁又使北岸侵蚀严重,易于滑塌,地形不稳,使秦后期及其以后的都城城址向渭河南岸发展。严重的河水与地下水污染,使渭河及附近无法供应城市生活用水,所以只能改用渭河南岸支流作为生活水源。而既不能作为生活水源,水量的暴涨暴缩及含沙量越来越大又使渭河难于航运,水患频发,是汉至隋唐及以后的城市选址不断向南发展的主要原因。

The location, construction, and migration ot ancient towns in the Guanzhong plains were closely connected with the hydrology and change of waterway of the Weihe River. History witnessed the course of changes from depending upon the Weihe River for water supply to turning to the tributaries for it, from using the Weihe River as the water highway through depending upon canals and ditches to lack of transporting conditions, moving the towns from the north bank to the south bank of the Weihe River and from a by-river location to a off-river location. In the long course of Chinese history, the Weihe River now rose violently, now shrank suddenly, making its water highly sand-loaded, suitable neither for drink nor for transport. This was the key reason for the continuously southward location of towns from the Han to the Sui and the Tang Dynasty and even in the later days.