|Certified Low Impact Hydropower Facilities|
The Hydro Division diverts water released from Lake McConaughy and/or the South Platte River into the Supply Canal, directs it through several lakes, three hydroelectric plants and delivers it to the irrigation system (during the irrigation season) or back to the Platte River (non-irrigation season).
The diversion for the Supply Canal is located 50 miles east of Central’s main storage reservoir, Lake McConaughy, and 75 miles west of Central’s irrigated area.
Completed in 1941, as were all other original sections of Central’s hydro-irrigation project, the Hydro Division’s major features include the Kingsley Hydroplant (which went on line in 1984) immediately below Kingsley Dam; a diversion dam just below the confluence of the North Platte and South Platte Rivers near the city of North Platte; a 75-mile-long Supply Canal with a capacity of 2,250 cubic feet per second; three hydroelectric plants on the Supply Canal; 28 lakes; and numerous checks, and automated control structures to control the flow of water.
The Gothenburg Control Center
The Hydro Division’s headquarters are in Gothenburg, Neb., also the site of the Control Center. The Control Center is staffed 24 hours a day, every day of the year. Control Center personnel monitor and remotely operate Central’s four hydroplants, two diversion dams (one owned by the Nebraska Public Power District), all Supply Canal control structures and two major canal systems overseen by Central’s Irrigation Division.
Communication is the key to Central’s automated control of its system. Central has its own digital microwave system, supplemented by buried cable and VHF radio links. All information is gathered at Remote Terminal Units (RTUs) and fed into the Control Center’s computers.
More than 500 alarm, control or telemetering points help operators control the system. About half of the points monitor and/or control functions of canal structures while the other half are located in the four hydroplants. The Control Center’s computers are programmed to receive data from the RTUs, check for alarm conditions and alert the operator to any abnormal readings. The computers alert the operator who may take corrective action by entering the necessary commands and/or dispatching Hydro Division personnel to the site should it be necessary. The operator’s control console includes a video screen that shows the current conditions at any selected location on the system. Control functions are accomplished on a keyboard.
The system was automated in the 1970s which enabled Central to 1) increase the generation of hydropower; 2) better manage the system under high-water conditions, i.e., sudden, heavy rainstorms; 3) reduce the incidence of spills; 4) reduce the need for maintenance of canals as a result of better control of flows; and 5) reduce operating costs.
RTUs at the diversion dams, Supply Canal structures and irrigation canals’ headgates are monitored and controlled in a similar fashion. Irrigation Division control structures are operated from the Holdrege and Bertrand Irrigation Offices during office hours. The Control Center operates the structures at all other times.
The North Platte Diversion Dam diverts water from the North and South Platte Rivers into the Supply Canal. Gates located in the Diversion Dam and the headgates of the Supply Canal are tied into Central’s supervisory control and data acquisition system and diversions and/or passing flows are controlled from Gothenburg.
Close coordination between generation of electricity at Kingsley Hydro and the Nebraska Public Power District’s Keystone Diversion Dam is required to ensure proper flows into NPPD’s supply canal and down the North Platte River. This fact led to the automation of Keystone Dam and the headgates of NPPD’s supply canal when Kingsley Hydro came on line in 1984. The dam and headgates are operated from Central’s Control Center and monitored at NPPD’s North Platte Hydroplant.
Three hydroplants — Jeffrey, Johnson No. 1 (J-1) and Johnson No. 2 (J-2) — are located on the Supply Canal. Each is similar in construction and appearance. Computers located at each plant relay data to the Gothenburg Control Center. If conditions deviate beyond certain limits, the computers alert control operators so corrections can be made, or if necessary, a technician can be sent to the plant.
The Platte River falls about seven feet per mile, while the Supply Canal drops approximately six inches per mile. Therefore, as the canal runs east, it gains about 6-1/2 fee of elevation per mile. At the Jeffrey and J-1 hydroplants, the water falls 113 feet through twin penstocks to turn two turbine-generator units at each plant (in other words, the plants have 113 feet of head). At J-2, the water falls 145 feet to spin a single turbine-generator unit.
The three Supply Canal Hydroplants underwent rehabilitation in 2001-2003 during which the original turbines were replaced, the generators rewound, switchyard transformers were replaced at J-2 and Jeffrey, and the static exciters in the generators were replaced. Each of the five turbine-generator units was originally rated at 18 MW, but capacity following the rehabilitation is now 20 MW at Jeffrey and J-1 and 23 MW at J-2.
The 50-MW Kingsley Hydroplant was completed in 1984. Its operation, like the other hydroplants, is controlled from Gothenburg.
All power generated at the hydroplants is sold at wholesale for distribution via the transmission system. All renewable energy certificates associated with the power generated at the Jeffrey, J-1 and J-2 plants are sold separately.
Hydropower, Recreation and Wildlife Habitat
The Hydro Division also provides benefits for recreation and wildlife. Two lakes in particular — Johnson Lake and Jeffrey Lake — are regulating reservoirs for downstream hydroplants. Johnson Lake, southeast of Lexington, covers 2,266 surface acres and its 11 miles of shoreline are circled with homes and cabins. The Nebraska Game and Parks Commission maintains two campgrounds at the lake that attract tens of thousands of people during the summer months. Jeffrey Lake, south of Brady, has 595 surface acres and is the second largest lake on the Supply Canal. More than 120 cabins and homes have been built on its shore and it also offers numerous recreational opportunities.
During excavation of the Supply Canal, Central opted to build dams across small canyons rather than building flumes or siphons to convey the water through the canyons. The result was 26 smaller lakes. Some — like Midway, Gallagher Canyon and Plum Creek Canyon — have recreational developments open to the public. Others offer opportunities for more primitive forms of outdoor recreation.
However, all of the lakes serve as fish and wildlife habitat. Since the Supply Canal carries water throughout the year, the area is a magnet for a wide variety of aquatic birds, fish and mammals. Central has opened the J-2 Hydroplant during the winter to afford and opportunity for the public to watch bald eagles that congregate along the canal below the plant to catch fish. A freestanding structure for public eagle-viewing is located below Kingsley Hydro on the shore of Lake Ogallala. The turbulence created by the operation of the hydroplants prevents the water immediately below the plants from freezing and creates excellent conditions for eagles and other waterfowl to catch fish.