During the early stages of civilization—when humans followed food resources, hunting and foraging in seasonal movements--the main concern about water was finding it. When people started building permanent settlements, it became necessary in many places to manage water resources.

Management systems can be divided into two basic types: systems built to ensure a sufficient and continuous water supply and systems built to protect against flooding--roughly, dams and dikes. Many cultures, including the Mayans and Southeast Asians, have impounded, diverted and transported water for agricultural and urban needs. Ancient ruins in the Middle East attest to early efforts in water resources management on a grand scale. For millenia, the Egyptians maintained extensive irrigation systems consisting of low earthen dikes along the Nile to control the water level for agricultural purposes. Large dam projects were also carried out in Egypt, though not always successfully...