From ancient times to the present century, Egyptian agriculture depended on the annual flooding of the Nile. Crop yields were predicted and taxes were set according to the river’s level in August, as measured by a series of Nilometers from Aswan down the valley to Roda and the Delta. Readings were sent to Egypt’s ruler and provincial governors; the basin-system of irrigation dictated that dikes must be breached at certain levels, making the Nile’s rise essential to the whole nation. A reading of 16 ells (8.6m) foretold the valley’s complete irrigation; significantly more or less meant widespread flooding or drought. Public rejoicing followed the announcement of the Wafa al-Nil (“Abundance of the Nile”), while any other verdict caused gloom and foreboding.