SEARCHING FOR THE SOURCE
The depleted Platte River looks to snowpack in the Rocky Mountains to fill its drought-seized channels.
ALGIS J. LAUKAITIS
The headwaters of the North Platte River can be found in a mountain meadow in the Rabbit Ears Range, not far from Grizzly Creek and Little Grizzly Creek.
This is northern Colorado high country, once the home of the grizzly bear and gray wolf.
Today, the landscape is a paradise for trout fishermen and kayakers. But it is much more.
It is also the source of most of the water that flows into the Platte, Nebraska's longest and most important river.
"The Platte River is critically important to Nebraska, providing water for irrigation, as well as groundwater, and habitat for endangered species and water for hydropower and municipal and industrial uses and recreation," said Ann Bleed, acting director of the Nebraska Department of Natural Resources.
The North Platte River is one of two major rivers that feed into the Platte River, which flows across Nebraska like an undulating thread before emptying into the Missouri River and eventually into the Gulf of Mexico. The other is the South Platte, whose headwaters can be found in the high country of central Colorado. But the South Platte's flows vary, making the river an unreliable resource. And there are no big dams or reservoirs on the South Platte that benefit Nebraska.
"The South Platte River is not a big contributor - not by volume - and it's not terribly reliable either," said Michael Jess, associate director of the University of Nebraska-Lincoln Water Center. He was the state's top water official for 24 years.
Hydrologists say the North Platte is most vital to Nebraska, contributing slightly more than 1 million acre-feet of water annually, compared with fewer than 500,000 acre feet from the South Platte. An acre-foot of water covers an acre to a depth of one foot, enough to meet the water needs of an average household for a year.
Most of the water in the North and South Platte rivers comes from snow piled high in mountain meadows and valleys. Hydrologists call it snowpack, which is measured not in feet but in moisture content. The heaviest snows typically fall in March and April. And when the snow melts in late spring and early summer, the water runs into tributaries and flows downstream.
In good years, snowpack in the headwaters of the North Platte River can fill up reservoirs and provide enough water to meet the needs of three states - Colorado, Wyoming and Nebraska. But when snowpack is below normal, those reservoirs take on a critical role, providing precious water to a semi-arid region. This year, farmers, ranchers and irrigation districts have been encouraged by early winter snowfall in the Rockies.
Colorado lays claim to some of the North Platte water that comes from the headwaters in the form of snowmelt. Wyoming captures the rest of the spring runoff behind six major dams and reservoirs: Seminoe, Kortes, Pathfinder, Alcova, Glendo and Guernsey.
Together, they make up the North Platte Project, which provides water to irrigate more than 300,000 acres in Wyoming and Nebraska.
"Seventy-five percent of the water stored in Wyoming is for the benefit of irrigators in Nebraska's Panhandle," said Tim Anderson, a spokesman with the Central Nebraska Public Power and Irrigation District. "Those reservoirs were built for the irrigation interests in Nebraska in the early 1900s."
Central has a special interest in the North Platte River because its water eventually ends up in Lake McConaughy near Ogallala. With a storage capacity of nearly 1.8 million acre-feet, McConaughy is the largest reservoir on the Platte River system.
Lake McConaughy also gets a substantial portion of its water from return flows after farmers and ranchers upstream use it to irrigate crops. Some of the irrigation water runs off fields into tributaries and other drainage systems and returns to the river.
However, return flows have been reduced because the drought has made less water available to release from upstream dams. Central also claims that unregulated groundwater wells upstream have depleted the river.
By spring 2005, six years of drought had so drastically reduced the amount of water stored in the North Platte River reservoirs that more than half of the 22-mile-long Lake McConaughy was dry. Central said Lake McConaughy started the 2005 irrigation season at 35 percent of its storage capacity - the lowest since it was built more than 50 years ago.
The main reason: Snowpack in the Rocky Mountains was below average during the previous five years. Total inflows into the reservoirs on the North Platte have dropped dramatically since 1999, according to the U.S. Bureau of Reclamation's office in Casper, Wyo. In 2002, inflows were 118,000 acre-feet, an all-time low for a century of record keeping. By comparison, in 1999, total inflows into those reservoirs were 915,000 acre-feet.
"Snowpack ultimately is everything - when it comes to the reservoirs, as well as meeting the needs, particularly the agricultural needs, of both Wyoming and Nebraska," said John Lawson, who oversees the North Platte River Basin for the U.S. Bureau of Reclamation.
Poor snowpack forced the bureau to reduce annual releases from its reservoirs to about 600,000 acre-feet of water-about half the normal yearly amount, Lawson said.
"We are starting to spread it really thin," Lawson said.
Last summer, Central's 1,200 irrigation customers in Nebraska received only 6.7 inches of water instead of their usual allotment of 18 inches, Anderson said.
But the water stored in Lake McConaughy is important for another purpose: hydroelectricity.
Nearly 80 percent of Central's annual revenues come from the generation and sale of electricity. The less water released from Lake McConaughy, the less revenue for the Holdrege-based district.
In 2004, Anderson said Central was looking at a $3 million deficit caused by reduced hydropower generation.
Central operates hydroelectric plants at Kingsley Dam at the east end of Lake McConaughy and other sites downstream. The Nebraska Public Power District also uses the water to cool its generators at Gerald Gentleman Station, a coal-fired power plant near Sutherland, and to generate electricity at its hydroelectric plant near North Platte.
About 90,000 acre-feet of water in Lake McConaughy is held in an "environmental account" administered by the U.S. Fish and Wildlife Service. The agency is supposed to use the water to sustain critical habitat in central Nebraska for the whooping crane, piping plover, least tern and pallid sturgeon - all endangered or threatened species. But because of the drought, the agency released no water in 2003, 2004 and 2005 for this purpose.
Below Lake McConaughy, the Platte River gets a significant amount of its flows from groundwater in nearby aquifers. Recent studies in the Platte basin have shown a direct connection between groundwater and surface water. Groundwater flows to and from the river, depending on the location.
"It looks like half - if not 60 percent - of the water in the Platte River comes from groundwater, but it depends on where you are in the Platte," said Jim Goeke, a professor and research hydrogeologist with UNL's Conservation and Survey Division/School of Natural Resources. "The Platte River changes its character as it flows across the state."
Groundwater becomes more important to the Platte as it skirts the edge of the Sandhills - a vast area in north-central Nebraska made up of grassy dunes. The Ogallala, one of the largest aquifers in the world, underlies the Sandhills. Goeke said water flows easily through those sandy soils and into the Platte as it moves east toward Grand Island.
A few miles past Columbus, the Platte gets its first big contribution of water from Nebraska rivers. Until that point, the Platte has relied on snowpack, rain and return flows from irrigation for most of its water. But near Columbus, the Loup River flows into the Platte. More water comes from the Elkhorn River when it meets the Platte above Ashland.
The Loup and Elkhorn, fed by groundwater from the Sandhills region, contribute most of the water in the Platte's lower reaches. Cities like Lincoln and Omaha depend on those rivers for a constant water supply for their growing populations.
The Metropolitan Utilities District is the latest to tap into the Platte River. The Omaha-based utility is building a $300 million well field and water-treatment plant along the Platte between Saunders and Douglas counties.
Near Ashland, the Lincoln Water System has sunk wells on an island to pump water from under the river bed. The water is treated nearby and piped to Lincoln.
So Lincoln residents drink water from Sandhills rivers and from snowmelt that traveled more than a thousand miles from a mountain meadow to replenish the saturated soils beneath the Platte River in eastern Nebraska.
