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Water balance. The law of water balance states that the inflows to any water system or area is equal to its outflows plus change in storage during a time interval. [2][3] In hydrology, a water balance equation can be used to describe the flow of water in and out of a system. A system can be one of several hydrological or water domains, such as ...
A chart datum is the water level surface serving as origin of depths displayed on a nautical chart and for reporting and predicting tide heights. A chart datum is generally derived from some tidal phase, in which case it is also known as a tidal datum. [1] Common chart datums are lowest astronomical tide (LAT) [1] and mean lower low water (MLLW).
Hydraulic head or piezometric head is a specific measurement of liquid pressure above a vertical datum. [1][2] It is usually measured as a liquid surface elevation, expressed in units of length, at the entrance (or bottom) of a piezometer. In an aquifer, it can be calculated from the depth to water in a piezometric well (a specialized water ...
Static level is the level of water in the well when no water is being removed from the well by pumping. [8] Water table is the upper level of the zone of saturation, an underground surface in which the soil or rock is permanently saturated with water. [9] Well yield is the volume of water per unit time that is produced by the well from pumping. [8]
Water level, also known as gauge height or stage, is the elevation of the free surface of a sea, stream, lake or reservoir relative to a specified vertical datum. [1]
Flood stage. Flood stage is the water level or stage at which the surface of a body of water has risen to a sufficient level to cause sufficient inundation of areas that are not normally covered by water, causing an inconvenience or a threat to life and property. When a body of water rises to this level, it is considered a flood event.
Water level (device) A water level device showing both ends at the same height. A water level (Greek: Aλφαδολάστιχο or (υδροστάθμη) [Alfadolasticho]) is a siphon utilizing two or more parts of the liquid water surface to establish a local horizontal line or plane of reference. It is used to determine the apparent ...
Stream gradient (or stream slope) is the grade (or slope) of a stream. It is measured by the ratio of drop in elevation and horizontal distance. [1] It is a dimensionless quantity, usually expressed in units of meters per kilometer (m/km) or feet per mile (ft/mi); it may also be expressed in percent (%). The world average river reach slope is 2 ...