Name : Zaid Hadi ObeidCivil engineering /water resources department

"Floods" A flood is an unusually high stage in a river, normally the level at which the river overflows its banks and inundates the adjoining area. The damages result from floods in terms of loss of life, property and economic loss due to disruption of economic activity. The hydrograph of extreme floods and stages corresponding to flood peaks provide valuable data for purposes of hydrologic design. Further, of the various characteristics of the flood hydrograph, possibly the most important used parameter is the flood peak. At a given location in a stream, flood peaks vary from year to year and their magnitude constitutes a hydrologic series which enable one to assign a frequency to a given flood-peak value. In the design of practically all hydrologic structures the peak flow that can be prospective with an assigned frequency (1 in 100 years) is of major importance to adequately proportion the structure to accommodate its effect. The design of bridges, culvert waterways and spillways for dams and estimation of scour at a hydraulic structure are some examples wherein flood-peak values are required.

Name : Zaid Hadi ObeidCivil engineering /water resources department

"Water Table"

A water table is the free water surface in an unconfined aquifer. The static level of a well penetrating an unconfined aquifer indicates the level of the water table. The water table is nearly constant in motion adjusting its surface to achieve a balance between the recharge and outflow from the subsurface storage. The inconstancy in the water level varies from season to season of the year, lowering of the groundwater table in a region due to heavy pumping of the wells and the rise in the water table in an irrigated area with poor drainage, are some common examples of the inconstancy of the water table. The water table follows the topographic features of the surface. If the water table intersects the land surface the groundwater comes out to the surface in the form of springs or seepage. Sometimes a lens or localized path of impervious stream can occur inside an unconfined aquifer water. Such a water table retained around the impervious material is known as perched water table. Usually the perched water table is of limited extent and the yield from such a situation is very small. In groundwater exploration a perched water table is quite often confused with a general water table.