MICROFICHE REFERENCE LIBFUUW - Cd3wd.com

2.2.1 Discharge or Capacity (Q)Discharge is the quantity of water per unit time (e.g., cubic feetper second, cfs; gallons per minute, gpm) whichthelifting device or pumpdelivers.Since losses may occur with a device or pumping system, dischargeis usually taken to be the quantity/time measured at the point where thewater leaves the device or pump.Discharge depends on the size of thewater lifter and the speed at which it is operated.2.2.2 Head (H)The term head, as applied to water lifting, has several components,each one a specific form of energy present in the lifting system. Inmost irrigation and drainage applications, head terms are usuallyexpressed as the height of a column of water which contains an equalamount of potential energy, e.g., feet of water. The components of head,as they normally apply to irrigation and drainage, are as follows:(a) Static suction head (HSSH) or submergence is the height ofsupply-water, if any, which exists above a pump centerline,when the system is at rest. In devices, which have no suctioncapability,HSSHis the height of water above the device'sinlet elevation, i.e., the elevation at which the minimumsubmergence Ims) necessary to have a discharge greater thanzero from the device exists.(b) Static suction lift (HssL) is the vertical distance from thestatic water level to the pump centerline where the water supplyexistsbelow the pump.