Laserfiche WebLink
<br />Upstream blanket. An impervious blanket placed on the reservoir floor and <br />abutments upstream of a dam. For an embankment dam, the blanket may be <br />connected to the core. <br /> <br />Valve. A device fitted to a pipeline or orifice in which the closure member <br />is either rotated or moved transversely or longitudinally in the waterway so <br />as to control or stop the flow. <br /> <br />a. Hollow jet valve. A device for regulating high-pressure outlets. <br />Essentially, it is half a needle valve in which the needle closure <br />member moves upstream toward the inlet end of the valve to shut off <br />flow. As there is no convergence at the outlet end, the flow emerges <br />in the form of an annular cylinder, segmented by several splitter <br />ribs for admitting air into the jet interior to prevent jet instabil- <br />ity. <br /> <br />b. Regulating sleeve valve. A valve for regulating high pressure outlets <br />and ensuring energy dissipation. Inside the valve there is a <br />fixed-cone, pointed upstream, which ensures dispersion of the jet. <br />Outside the valve a cylindrical sleeve moves downstream to shut off <br />flow by sealing on the periphery of the Cone. <br /> <br />Volume of dam. The total space occupied by the materials forming the dam <br />structure computed between abutments and from top to bottom of dam. No <br />deduction is made for small openings such as galleries, adits, tunnels, and <br />operating chambers within the dam structure. Portions of powerplants, locks, <br />spillway, etc., should be included only if they are necessary for the <br />structural stability of the dam. <br /> <br />Watershed divide. The divide or boundary between catchment areas (or drainage <br />areas) . <br /> <br />Wave runup. Vertical height above the stillwater level to which water from a <br />specific wave will run up the face of a structure or embankment. <br /> <br />Weir. A notch of regular form through which water flows. <br /> <br />a. Weir, broad-crested. An overflow structure on which the nappe is <br />supported for an appreciable length in the direction of flow. <br /> <br />b. Weir, measuring. A device for measuring the rate of flow of water. <br />It generally consists of a rectangular, trapezoidal, triangular, or <br />other shaped notch, located in a vertical, thin plate over which <br />water flows. The height of water above .the weir crest is used to <br />determine the rate of flow. <br /> <br />c. Weir, ogee. A reverse curve, shaped like an elongated letter "S." <br />The downstream faces of overflow spillways are often made to this <br />shape. <br /> <br />Wind setup. The vertical rise in the stillwater level at the face of a <br />structure or embankment caused by wind stresses on the surface of the water. <br /> <br />-13- <br />