Archives May 2015

Flood Warning Issued for North Platte River above McConaughy

Flood Warning Issued for North Platte River above McConaughy

The National Weather Service has issued flood warnings for the middle of this week along the North Platte River above Lake McConaughy.

Citing “heavy and prolonged rainfall” in the watershed the river drains in Wyoming, the warning indicates that flows in the river could reach 5,000 to 6,000 cubic feet per second (cfs) on Tuesday and above 8,000 cfs by Thursday in stretches of the river near Mitchell, Neb. Water is being released from Glendo Reservoir in Wyoming as it nears the flood pool. On Tuesday, the reservoir was at about 98 percent capacity.

If the high flows materialize, the North Platte River above Lake McConaughy could reach a flood stage as high as 10.2 feet near Mitchell (flood stages vary at different locations due to channel width, depth and other factors), which would be near record highs.

At the Lewellen gauge, which is just above Lake McConaughy, the river is projected to rise to a flood state of 8.5 feet by Saturday, which according to NWS data, would represent moderate flooding at and near the gauge site. Estimates of flow rates into the reservoir were not immediately available.

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National Weather Service graphic

However, high flows along the North Platte River below Lake McConaughy are not expected to be an issue. As of May 26, the reservoir’s elevation was 3,253.2 feet, which is about 12 feet below the maximum elevation of 3.265.0 feet. Inflows, although expected to rise this week, were at 3,500 cfs on Tuesday while outflows were around 300 cfs. In short, the reservoir has capacity to store the high inflows expected this week.

At the same time, flows in the South Platte River are beginning to decline in Colorado, although more rain could alter that picture. At the Roscoe and North Platte gauges in Nebraska, the South Platte is expected to reach a peak on Wednesday or Thursday before beginning to decline. However, the South Platte is projected to continue to carry higher than normal flows for the next few weeks.

Only minor lowland flooding is currently projected for the Platte River in central Nebraska.

National Dam Safety Awareness Day is May 31

National Dam Safety Awareness Day is May 31

National Dam Safety Awareness Day occurs on May 31 of each year to commemorate the failure of the South Fork Dam in Johnstown, Pennsylvania in 1889. The dam failure resulted in the loss of more than 2,200 lives and is the worst dam failure in terms of fatalities in the history of the United States.

Photo courtesy of National Park Service

Aftermath of Johnstown Flood. Photo courtesy of National Park Service

National Dam Safety Awareness Day was created to encourage and promote individual and community responsibility for dam safety, as well as to provide information on what steps can be taken to prevent future catastrophic dam failures. A secondary goal is to promote the benefits dams offer to communities.

For 30 years, the federal government has been working to protect Americans from dam failure through the National Dam Safety Program (NDSP). The NDSP, which is led by the Federal Emergency Management Agency (FEMA), is a partnership of the states, federal agencies, and other stakeholders to encourage individual and community responsibility for dam safety.

While Kingsley Dam, which impounds the largest reservoir in Nebraska, is the primary focus of Central’s dam safety efforts, Central also has prepared emergency action plans for dams impounding Jeffrey Lake and Johnson Lake.

The possibility that Kingsley Dam (or Jeffrey or Johnson dam) will fail is extremely remote, but Central would like the public to know that it is prepared in the event of an emergency that threatens the integrity of its dams.

Central updates and revises each of its emergency action plans (EAP) annually and distributes the revised plan to a designated list of local, state and federal entities. The purpose of the EAPs is to provide maximum early warning to all persons downstream of the dam involved in the unlikely event of a failure (catastrophic or otherwise) of the structure. In addition to providing early warning, Central’s objective is to minimize or eliminate danger to people and property downstream.

EAPs contain information pertaining to how potential conditions that could cause or signify an emergency situation and steps to follow to evaluate those conditions. Such conditions include inordinately high flows, adverse weather conditions, and any situations discovered during routine inspections of the structures.

Central’s dams are inspected regularly by well-trained employees, annually by Federal Energy Regulatory Commission (FERC) personnel, and at five-year intervals by independent engineering consultants. Central also conducts functional exercises of the EAPs every five years – as required by the FERC — that involve representatives from the numerous agencies that would be involved. A functional exercise for Kingsley Dam is scheduled to take place at Central’s Gothenburg Division headquarters on June 10.

So you can rest easy tonight knowing that you probably don’t have to worry about failure of one of Central’s dams, but also that plans are in place to respond to such a calamity … just in case.

Visit http://engineeringstrongersafer.net/ for more information on National Dam Safety Awareness Day.

Additional information on national dam safety is available at: www.fema.gov/protecting-our-communities/dam-safety

 

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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Image2_Roscoe_gauge_5-11-15

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.


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