The earliest water law systems developed when social groupings settled in river valleys and around water points where they could find water to irrigate land and satisfy their religious and social needs. This is the case of the hydraulic civilizations of ancient Egypt along the Nile, Mesopotamia on the Tigris and the Euphrates, the Mohan-Jo Daro and the Indus Valley, ancient China and the ancient Hebrew civilization. Water was often associated with religious entities. Due to the collective interest in land and water, these resources became public property to which community members had a right of access. Rules were introduced to ensure equitable and rational water distribution and the defence against floods. They were tailored to climatic conditions, religious beliefs and other factors. Thus, they were more detailed and restrictive where water was scarce and when the operation and maintenance of waterworks and canals required a large amount of labour, a high level of organization and a water administration. The decadence or disappearance of many of the earliest civilizations might have been due to decreased concern by the administration for the maintenance of hydraulic structures, this meaning that adequate management of water resources is a prerequisite for survival and economic development.