简要回答你的问题:
1. (the)managing of the water resource: managing 是名词化的动名词,of the water resource 为其定语。managing 与 the water resource 存在动宾关系。
2. managing the water resource: managing 是动名词,具备了动词的基本特征,可以接宾语或状语。the water resource 为其宾语,还可加状语,例如:managing the water resource properly (妥善管理水资源)