Desilting structure at the Gualanday Canal Headworks, Coello Project, Colombia, S.A. ; Desilting structure at the Gualanday Canal Headworks, Coello Project, Colombia, S.A.: model study

CER61SSK29. ; Prepared for Tipton and Kalmbach, Inc., Denver, Colorado. ; April 1961. ; Model studies were conducted in the Hydraulics Laboratory at Colorado State University to develop a more efficient sediment excluder to replace the existing desilting structure at the Gualanday Canal head works. A plan of the recommended structure is shown in Fig. 13. The principal features of the excluder are: (1) a circular arc settling basin, 9.5 meters wide with a sloping bottom inclined radially at 4:1 and (2) two sluice tunnels connecting the settling basin to the existing sluice gates to discharge the sediment back into the river channel downstream of the diversion works. At the beginning of the sluice tunnels there is a circular arc sill raised to elevation of 459.9 m (except for a 3-meter section which is at elevation 456.0 m). The purposes for this sill are to increase the depth of water in the settling basin at low flows to encourage settling of suspended materials and to divert sediment free water into the canal. Also at high discharges the sill will deflect the flow, creating a local bend in the flow path and will convey much of the bed load bypassing the settling basin along the inside of the curve and over the control dam. The structure was estimated to be from 90 to 100 per cent effective for excluding the river bed load at discharges below 25 c.m.s. and from 75 to 95 percent effective at discharges above 25 c.m.s.