Flow attenuation plan designed to protect nesting habitat

Flow attenuation plan designed to protect nesting habitat

With the summer months approaching, Central would like to provide a reminder about operations at Johnson Lake, specifically the requirement to adhere to a plan to protect nesting habitat for two threatened/endangered avian species along the Platte River.

The Flow Attenuation Plan, or “Spike-Flow Plan” (Plan), was developed several years ago with input from the U.S. Fish and Wildlife Service and the Nebraska Game and Parks Commission. It is intended to help attenuate (reduce) flows on the Platte River below the Overton measuring gauge during the least tern and piping plover nesting seasons.

The Plan is designed to keep Platte River levels at lower levels, thus reducing the chances of flooding nests located on sandbars. The Plan requires Central to use Elwood Reservoir and up to 2,500 acre-feet of space in Johnson Lake and immediately above the J-2 Hydroplant to help attenuate river flows. It enables Central to respond to large rain events during the irrigation season and reduce the release of rejected irrigation water to the river.

Water is released from Lake McConaughy during the irrigation season to serve more than 100,000 irrigated acres primarily in Gosper, Phelps and Kearney counties. Water from Lake McConaughy takes four to five days to travel the 125 miles to the headworks of the irrigation systems. The Supply Canal also collects rainfall runoff in its watershed, so its flow may vary beyond what is diverted at the North Platte Diversion Dam.

On occasion, large rainfall events occur in the Platte River basin and Central’s irrigated area. Heavy rainfall increases river flows and often prompts many irrigators to stop taking water. Since these rain events sometimes occur with little notice, and water has already been released to meet irrigation demands, a large quantity of water may be moving through Central’s system when it isn’t needed for irrigation (remember the travel time between Lake McConaughy and the irrigated area). This excess water must either be regulated in Central’s system or returned to the river. Returning the water to the river means losing precious storage water for irrigation purposes.

To have 2,500 acre-feet of space in Johnson Lake to hold rain and rejected irrigation water, the lake must be kept at the lower end of normal levels. From June 1 to Aug. 15 each year, Johnson Lake will be operated near the low end of the normal operation range (see Johnson Lake Elevation Graph) so that space is available if attenuation is required. When attenuating flows, Johnson Lake levels will increase until the water is released to the river at low flows or diverted to the irrigation canals. The water levels will then decline to the lower end of the operating range in preparation for another attenuation event.

Help Prevent an Invasion: Clean, Drain and Dry to Keep Invasive Aquatic Species Out of Nebraska Waters

Help Prevent an Invasion:  Clean, Drain and Dry to Keep Invasive Aquatic Species Out of Nebraska Waters

A small aquatic species, not much bigger than your thumbnail, poses a threat to Nebraska’s lakes, reservoirs and associated power-generating facilities.  Once established, the critters are extremely difficult and expensive to remove.

The creature is the zebra mussels (and their relative, the quagga mussel).  But Nebraska is not without defenses.  As the Memorial Day weekend — and the summer recreation season — approaches, boaters and recreation-seekers can help by simply cleaning, draining and drying a boat, trailer and related equipment to help prevent the invasion.

The zebra mussel has caused enormous problems in other parts of the country and has been detected in Nebraska in a lake at Offutt Air Force Base and on a dock on the South Dakota side of Lewis & Clark Lake.  Evidence of zebra mussels was also discovered on a boat and trailer at Harlan County Lake, although the specimens had died before the boat entered the water.  Whether it spreads to other lakes and rivers depends to a large degree on the public’s vigilance.  The mussels are one of many invasive species found in various lakes and rivers that can cause damage to boat motors and clog cooling water intakes at power plants.

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Pipes clogged by accumulation of quagga mussels.

The Central Nebraska Public Power and Irrigation District uses water to generate electricity at the Kingsley Hydroplant at Lake McConaughy and also at three hydroplants along the Supply Canal between North Platte and Lexington.  In addition, the Nebraska Public Power District uses water from Lake McConaughy to cool equipment at Gerald Gentleman Station near Sutherland, and to produce power at the North Platte Hydroelectric Plant.  Preventing aquatic invasive species from fouling intake pipes and other equipment is important to continuing Nebraska’s ability to provide low cost, reliable electricity.

“We’ve seen the devastation that zebra mussels have done to water bodies in other states,” said Central Senior Biologist Mark Peyton.  “They dramatically change the fishery and natural balance of the lake or river.  What’s more, when they are in a system like the Platte River, it would be next to impossible to prevent them from infesting all the other water bodies associated with that system.

“Once a body of water is contaminated, monetary resources that could be used to improve and enhance recreational opportunities and wildlife value at the lakes are used instead to clean up and contain the mussels.  All in all, the mussels simply are not good for the system or for the people using the system.  We hope that people who use the lakes in Nebraska don’t become complacent about the threat because it’s out there, it’s real.”

A freshwater mollusk native to eastern Europe and western Asia, the zebra mussel — so named for its striped shell — was first detected in North America in 1988 in Lake St. Clair, a small lake between Lake Huron and Lake Erie.  The first specimens probably arrived in the ballast water of ships that sailed from a freshwater port in Europe.  It has since spread throughout the Great lakes region and to river systems in the Midwest, including the Ohio, Illinois, Arkansas, and Mississippi rivers.

How can such a small mollusk create such problems?  First, they reproduce prolifically.  A single female, which has a life span of up to five years, can lay more than a million eggs during a single spawning season.  Second, the mussels anchor themselves to hard surfaces in huge numbers.

Water intake pipes at factories, water treatment plants, and power plants have been clogged by the buildup of mussels, requiring difficult and expensive removal.  Beyond industry, zebra mussels can infest boat hulls and motors, docks, lifts and any other structure in the water.  The shells of dead mussels can accumulate in great quantities on swimming beaches, the sharp edges posing a threat to swimmers’ feet.

In addition, because they feed by filtering algae and plankton from the water, they can disrupt the food chain at its base.

A relative of the zebra mussel, the quagga mussel, has been discovered at Julesburg Reservoir in the South Platte Basin, less than 50 miles from Lake McConaughy.  The quagga poses the same threat to industry and recreation as the zebra mussel and has been found in many western lakes.  Nationwide, the economic impact of the mussels comes to billions of dollars.

Karie Decker, formerly the coordinator for the Nebraska Invasive Species Project and now an assistant division administrator for the Nebraska Game and Parks Commission’s Wildlife Division, said, “Everyone who uses our lakes for any reason, be it recreation, irrigation, or power production, has a stake in preventing the spread of these species.  Quite literally, they can ruin a lake.”

She said there would be no way to eradicate the mussels if they gained a foothold in Lake McConaughy.

“We could only hope to contain them and even that would be expensive for Nebraska,” she said.

At the root of the state’s effort to educate the public about the threat posed by the mussels is the slogan, “CLEAN. DRAIN. DRY.”  Lake visitors are urged to clean, drain and dry any watercraft and recreational equipment before putting them into the water.

“Inadvertent human transport is the main pathway for introducing the mussels to other lakes,” Decker said.  “We want to make sure people aren’t transporting water that may contain larvae from one lake to another in boats, live wells, bait buckets, waders, or even vegetation attached to boat trailers.”

Decker said it doesn’t take long to inspect boats.  The more difficult task, she said, is simply making people aware of the need to do so and getting them to follow through with regular inspections.

The public is the only line of defense and Nebraska needs help to repel the invader.  For more information about the invasive mussels, visit the Nebraska Invasive Species Project’s web site at http://snr.unl.edu/invasives.

South Platte Flows on the Rise

South Platte Flows on the Rise

Precipitation in recent days in Colorado’s South Platte River watershed has raised flows in the South Platte River entering Nebraska.  The South Platte River is expected to experience increased flows in Nebraska through next week, and may cause some flooding problems in some areas.  (See charts below from the National Weather Service.)

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In anticipation of flows in the Platte River being above target flows set by the U.S. Fish and Wildlife Service, Central’s board of directors met in a special board meeting on Fri., May 8 and approved (subject to legal review and approval by the other parties) agreements to divert excess river flows into the E65 Canal and Elwood Reservoir for groundwater recharge purposes and to augment instream flows.

The agreements are part of efforts by Central, Tri-Basin Natural Resources District, the Nebraska Department of Natural Resources, the Nebraska Community Foundation, and the Platte River Recovery Implementation Program to utilize excess flows for beneficial purposes.

Pumping Water into Elwood Reservoir

Pumping Water into Elwood Reservoir

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The Central Nebraska Public Power and Irrigation District is in the process of partially filling Elwood Reservoir in preparation for the 2015 irrigation season.

With irrigation customers limited to 12 inches/acre over the coming irrigation season, a completely full Elwood Reservoir will not be necessary.  Instead, Central will divert 15,000 acre-feet of water into Elwood, raising the reservoir’s elevation to about 2,602 feet by the end of May.  The normal maximum elevation is 2,607 feet.

By limiting the amount of water pumped into the reservoir, Central will be able to conserve thousands of acre-feet in Lake McConaughy.  Central’s storage rights require that water pumped into Elwood Reservoir for irrigation purposes must be a transfer of storage water from Lake McConaughy.

To accomplish the fill schedule, Central plans to operate two of the three pumps at the Carl T. Curtis Pump Station in April, and then use one pump during May to reach the intended level.  The pumping process will raise the reservoir’s elevation by 14 feet between April 1 and the end of May.

In addition to providing water for irrigation customers, inflows into the reservoir will benefit the fishery at the lake, as well as providing some incidental groundwater recharge benefits.  Central, in cooperation with Tri-Basin NRD and the Nebraska Department of Natural Resources, had diverted 15,000 acre-feet into the reservoir for groundwater recharge last year – water that was in excess of target flows and other uses in the Platte River – and then added another 15,000 acre-feet for recharge purposes in December and January.  Water that is pumped into the reservoir is allowed to seep into the ground, thereby helping the area’s groundwater level, as well as augmenting base flows in the Platte River as the water eventually moves underground back to the river.

E-65 Canal Groundwater Recharge Project

E-65 Canal Groundwater Recharge Project

Above normal flows in the South Platte River this fall has allowed Central to partner with Tri-Basin Natural Resource District and the Nebraska Department of Natural Resources to divert excess flows into the E-65 canal system and Elwood Reservoir for groundwater recharge. Agreements allow a total of 10,000 acre-feet of water total to be diverted into Central’s system of canals and lakes, allowing for Tri-Basin and the State of Nebraska to get credit for recharge in the Republican and Platte River basins. Diversions began on December 10, 2014, and so far approximately 6,500 a-f of water has been diverted. Elwood reservoir has risen five feet in elevation due to this project.

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This photo shows icy water held in the E-65 canal system from miles 19.3 to 20.1, allowing for groundwater recharge from Johnson Lake to the area shown above near Smithfield.

 


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