密云是北京市水利资源较为丰富的县，全县共有主要河流14条，其中潮河、白河东西分流，纵贯全县，年均自产地表水1亿 m3。但旧中国疏于治理，水患灾害频繁，灌溉水平更是低下。1949年全县有水浇地0．63万亩，仅占耕地面积的1．3％。水利建设经历了一个从小到大，从土到洋的发 Miyun is a county rich in water conservancy resources in Beijing. There are 14 major rivers in the county. Among them, Chaohe and Baihe divert water from east to west and run through the whole county. The average annual production of surface water is 100 million m3. However, neglect of governance in old China, floods frequent disasters, irrigation levels are even lower. In 1949, there were 06,300 mu irrigated land in the county, accounting for only 1.3% of the cultivated land area. Water conservancy construction has experienced a from small to large, from earth to ocean hair