中文摘要：

浪底水利枢纽工程投入运用以来，下游河道的来水来沙条件发生了改变，下游引黄灌区面临着新的形势。分析了小浪底水库建成前后下游河道水沙和边界条件的变化，研究了下游引黄灌区在新条件下所面，临的有利与不利因素。研究表明，小浪底枢纽建成后有利于缓解下游水资源供需矛盾，在一定程度上改善了下游生态环境。在水库蓄水拦沙初期，下游灌区引水中的泥沙含量大幅降低，灌区引沙量明显减少。另一方面，由于水库的拦沙作用下游河道来沙量减少，造成边界条件改变，有可能引起灌区引水条件恶化和粗沙入渠加剧淤积的问题。

英文摘要：

Irrigation districts along the Lower Yellow Rive are facing a new situation tor the initial operation ot xiaolangai project. Changes of water-sediment and boundary condition before and after operation of Xiaolangdi reservoir are analyzed in theis paper. The results show that the reservoir brings both advantage and disadvantage to irrigation districts. The conflict between supply and de- mand of water resources is eased, and the ecological environment is improved. After the reservoir initial operation, capacity and quantity of diversion sediment in irrigation districts from the Lower Yellow River is relatively less than that before. On the other hand, diversion condition from the Yellow River can make it worse for river boundary＇s change. Deposition problem of trench can ac- cordingly make it serious for coarse sediment inputting.