PROJECT OVERVIEW Little Bow Headworks System: The Little Bow Headworks System is located in the Town of High River, Alberta. The project is used to divert water from the Highwood River, via a canal to the upper Little Bow River. The diverted water is used by domestic, municipal, and agricultural users in the Little Bow River. The Little Bow Diversion Project is operated and maintained by Alberta Agriculture and Irrigation, Water Infrastructure and Operations Branch, Bow Operations Calgary work unit. The canal system delivers a maximum flow of 8.5 m^3/s (300 cfs) to the Little Bow River during periods of high flow in the Highwood River. It also delivers a minimum flow of 0.57 m3/s (20 cfs) in the winter months for the downstream domestic users. A contract operator makes the necessary gate adjustments as required on behalf of AGI. The concrete river intake structure includes four gated conduits, two of which are designed to accommodate winter operations. Downstream of the Intake Structure, there is a Fish By-Pass Structure which uses vertical screens to covey fish back to the Highwood River via pipeline to the downstream side of the intake structure. The structure consists of cast-in-place concrete flume, fish screens, fish screen cleaning system, fish pumping system and fish by-pass pipe. The fish pumping system is comprised of 4 pump-motor assemblies which are operated using 4 variable frequency drives (VFD). The maximum design discharge capacity of the pumping system is 0.447cms. The fish bypass pipe is a polyethylene pipe with a diameter of 700mm and routes the water, fish and debris back to the Highwood River on the downstream side of the intake structure.
The 4km long canal has a maximum design flow capacity of 8.5cms with a minimum winter design flow of 0.56cms and includes a various crossings and small hydraulic structures including a flood handling wasteway structure. Women’s Coulee Headworks System: The Women’s Coulee Diversion System is an integral component of the Little Bow River regional water management system. The system diverts water from the Highwood River about 8km SW of the Town of High River into Mosquito Creek, and ultimately into Twin Valley Reservoir. The WCD System consists of: Diversion Structure Diversion Channel Pipeline Inlet Structure with Fish Bypass Pipeline Pipeline and Pipeline Outlet Structure Women’s Coulee Canal and Dam Diversion Structure: The gated diversion structure is designed to divert a minimum discharge of 1.7m^3/s from the river. There are three vertical slide gates which are opened fully during the operating season as discharge control in the pipeline is visa the butterfly valves in the Pipeline Outlet Structure. Excess flow conveyed via the diversion structure is conveyed through the Fish Bypass Pipeline back to the Highwood River. Pipeline Inlet and Fish Bypass Structure: The cast in place concrete pipeline inlet and fish bypass structure is located at the downstream end of the diversion channel. A precast concrete fish bypass pipeline is provided to allow water and fish to be passed back to the river. The fish bypass consists of a 94m long, 1050mm diameter precast concrete pipeline that outlets back into the Highwood River approximately 65m downstream of the diversion structure. A 1067mm diameter electrically actuated medium duty slide gate at the upstream end of the fish bypass pipeline can be used to isolate the pipeline. A 1500mm diameter butterfly valve is provided at the upstream end of the PVC pipeline to open and close the pipeline. Fish Exclusion: Two drum fish screens are provided within the pipeline inlet and fish bypass structure. Pipeline: The pipeline consists of a 1500mm diameter DR51 PVC pipeline for the first 1472m and transitioning to a 1350mm diameter DR51 PVC pipeline for the remaining 3654m. The PVC pipeline was installed with a minimum soil cover of 1m. Seven pipeline turnouts exist along the pipeline. Pipeline Outlet Structure: A cast-in-place concrete pipeline outlet structure is located at the terminal end of the PVC pipeline. The terminal end of the PVC pipeline consists of a 1460 O.D. x 12mm thick fabricated steel pipe to a 1460 O.D. steel header pipe which has 5 steel pipes, each with a butterfly valve, installed at the springline of the steel header pipe. Discharge from the butterfly valves projects to a cast-in-place concrete impact basin baffle with a steel wearing plate with dissipate energy. Two 12” diameter and Three 14” diameter electrically actuated butterfly valves are provided. Women’s Coulee Dam and Appurtenant Structures: Women’s Coulee Dam is an earthfill embankment approximately 130 m long with a maximum height of 8.2 m. The embankment has an upstream slope of approximately 4H:1V and a downstream slope of 3H:1V to a pitrun gravel and fine filter toe berm. The upstream embankment slope is protected with riprap. The dam crest is approximately 5 m wide with a design top of dam elevation of 1071.45 m and full supply level of 1069.5 m. Releases from Women’s Coulee Dam are made via a single gated low-level outlet structure. The low-level outlet structure consists of a cast-in-place concrete inlet, 900 mm diameter precast concrete pipe, a 6.7 m high, 1.9 m wide by 2.7 m long cast-in-place concrete gatewell complete with an electrically-actuated heavy duty slide gate, and a cast-in place concrete Type III stilling basin outlet structure (13.1 m long, 2.1 m high, and 1.2 m to 2.5 m wide). Riprap erosion protection is provided for a length of 15 m downstream of the stilling basin outlet structure.
