The system skillfully takes advantage of the naturltopography and the eurved waterflowing pattern om the middle reach of the mingjiang river , thus combining water - bifurcation , flood - diversion , sand - dredging and water - controlling as a whole gravity irrigation system , which guarantees the chengdu plain a land of abundance 都江堰巧妙利用岷江出山口处的地形、水脉、水势、乘势利导，使堤防、分水、泄洪、排沙、控流相互依存，共为体系，保证了防洪、灌溉、水运和用水综合效益的发挥，孕育了举世闻名的“天府之国” 。
