Scientists hope to bring clarity to muddy issue

This is where science on the Kenai River gets down and dirty.

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The stench of rotting salmon wafts from the muck as Sally Swenson of GW Scientific tries to drop a cable behind the bucket of a backhoe before the hole by the river caves in. David Nyman, principal investigator for Restoration Science and Engineering, slogs through knee-deep mud with a board to brace the cable. The backhoe fills mud and rocks around the cable.

They are installing a string of buried temperature, pressure and conductivity sensors by the river to learn how groundwater influences salmon eggs buried in the river bottom.

"People have looked at fry and protecting riverbank habitat, and protecting the fish once they're out of the gravel. But there is less understanding of what affects them when they are in the gravel," said Michael Lilly, principal investigator with Fairbanks-based GW Scientific. "What's the environment that egg sees in terms of temperature and water chemistry? It's the interface between groundwater and surface water. Not much is known about the characteristics of that interface."

Education is a big part of the $142,000 project, one of several funded through a $340,000 U.S. Environmental Protection Agency grant administered by the Kenai Watershed Forum.

Development that affects groundwater could change river bottom temperature or water chemistry, affecting where salmon spawn or the survival of their eggs. It also could inject pollutants.

"Surface water is understood, because you can step in it," Lilly said. "In the past five years, they've come to a better understanding of wetlands. You can step in those."

The importance of groundwater is not well appreciated, he said. However, researchers believe groundwater contributes significantly to the flow of the Kenai River, and the river corridor is a prime area for development. Understanding groundwater is important in deciding issues such as the minimum size for subdivision lots, Lilly said.

"If you over-develop, will you impact the quality or quantity of groundwater that flows into the river? The problem is that it's very hard to go back once you impact groundwater," he said. "If you have too many septic systems, there's a huge infrastructure cost. You have to put in a sewer system. You can't go back and say, 'These should have been 5-acre lots.' You're trying to educate the public ... so that when they do development, they understand what they're managing."

At the Pillars state recreation site on the Kenai River, the researchers buried a string of temperature sensors beneath the river bottom near the bank. They laid temperature, pressure and conductivity probes on the river bottom farther out. They drilled three wells in a row on land near the river and fitted those with pressure and conductivity sensors. By each well, they installed underground temperature sensors.

They also buried soil moisture sensors in one pit near the riverbank and in another back from the water.

They planned to run cables from all the sensors to a radio. That will beam real-time readings to the Kenai River Center, which will route them to www.kenai-watershed.org on the Internet. Next month, researchers plan to complete a similar installation at the former state highway maintenance yard by the Kenai River in Soldotna.

The idea at both sites is to detect groundwater flowing toward the river or river water flowing into the ground. River and groundwater have different temperatures, so from temperature readings, researchers can tell them apart. Likewise, groundwater contains more dissolved minerals than river water. That affects electrical conductivity, so researchers also can use conductivity readings to distinguish the two. The pressure probes will detect changes in river level during storms, glacial runoff and snowmelt. At the Pillars, they also will detect the tide, which rises and falls 4 or 5 feet each day. Lilly said researchers will learn about permeability of the soil by studying groundwater flow as the river rises and falls.

Moisture probes in the pits will indicate how much rainwater seeps into the soil and how much leaves as surface runoff. They also will indicate when the ground freezes and thaws. There generally is a runoff peak in spring when the snow melts over frozen ground.

During summer, more water seeps into the ground.

"Water enters the river via groundwater, so there is more of a lag," Lilly said.

The researchers do not plan to drill through a layer of clay more than 20 feet below the surface, he said. That separates groundwater near the surface from pressurized layers deeper down. In Soldotna and at the Pillars, the river probably does not cut beneath it, either, he said. However, there could be gaps in the clay, and upstream, the river may cut beneath it.

"The wells around Kenai are highly artesian," Nyman said. "Underground, there's a highly pressurized system that probably pushes water into the river. Even at the Warren Ames Bridge, when the (Department of Transportation and Public Facilities) drilled a well in the 1960s, they tapped into an artesian system."

To learn more about the pressurized layers, the researchers will study private well logs, DOT geotechnical logs, private engineering studies and more. Lilly said they will produce an interim report in January and a more complete report in December 2001. However, it will take many years of study and instruments at additional sites to really understand how groundwater affects the river. He said researchers hope the Soldotna and Pillars sites will operate for 20 to 40 years.

Other projects funded by the EPA grant are a paper on Kenai River prehistory, an evaluation of the light-penetrating walkways now popular along the river, a drainage history of the lower Kenai River, a documentary about the Kenai watershed and salmon, and citizen watershed monitoring.