The
Central Nebraska Public Power and Irrigation District's
Hydro Division
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.
Hydroelectric
Power
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 to the
Nebraska Public Power District, which distributes the power throughout
the state.
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.
HYDRO
DIVISION -- MAP OF CENTRAL'S SUPPLY CANAL SYSTEM
(PDF file -- Acrobat Reader required)
Some
files within this document require a PDF reader. Click here
to download a free version of Adobe Reader from the Adobe
Web Site. |
|