Heavy with sand and silt, Alaska’s Copper River resembles nothing so much as a slurry pipeline as it carries to sea the outwash of dozens of glaciers in the Wrangell/St. Elias Mountains of Eastern Alaska.
So dirty is the water, the human eye cannot penetrate its cloudy surface. So large is the sediment load, it can be heard grinding against the rock walls of Wood Canyon as the muddy water roars toward the seas.
Two-hundred miles to the west and south, the Kenai River flows gray-green out of the mountains of the same name into an estuary where it begins to dump its sediment load, leaving thick deposits of mud along the riverbanks in places.
When the dirt in the water is measured in “nephelometric turbidity units” or what are usually just called NTUs, the dirty Copper registers 574 on average, but sometimes climbs to a maximum of 678, according to a report from University of California, Davis.
At Kenai River mile 11.5, where the fast-flowing waters of the mountain river sometimes flow out to sea and where the big, rising tides of Cook Inlet sometimes cause the river to flow back toward the mountains from which it came, the Kenai hits a maximum of about 55 NTUs, according to the Alaska Department of Environmental Conservation (DEC).
At its worst, the Kenai is more than 10 times cleaner than the Copper – the river famous for its world-famous Copper River king salmon. They are considered such a valuable, wild, unspoiled, fresh-from-Alaska prize that they were fetching prices of more than $55 per pound earlier this year.
The Kenai, too, is famous for its king and sockeye salmon. But other than that, the two rivers are very different.
The state of Alaska has now declared the water in one of them “impaired.”
It’s the Kenai
The DEC has issued a report concluding the lower reaches of the hugely popular glacial river only about 100 miles south of Alaska’s largest city – the river from which came the world-record 97-pound, 4-ounce king (Chinook) salmon, the river that attracts sockeye salmon anglers by the hundreds of thousands every summer, the river after which the entire Kenai Peninsula is named – is unacceptably dirty.
“…The Kenai River is getting a failing grade,” Alaska’s Energy Desk at Alaska Public Media reported last week. “The state is recommending that it be put on a list of polluted waterways.”
A “polluted” Kenai is great click bait. Some readers here, maybe many, are reading this story because of the pollution reference. APM headlined its story “State’s latest water quality report has bad news for popular Kenai River.”
That’s true to the extent the state wants to use the report declare the lower river “impaired,” but what turbidity means in terms of water quality in Alaska is a very, very confusing issue.
“You’ve got to keep it in context,” said Brock Tabor, a DEC water-quality specialist. “There is certainly debate within the scientific community….What is the definition of impaired, and what does that mean?”
There is no fixed level of turbidity at which water quality is considered to be “polluted.” There is only a relative standard, except where there isn’t.
The state’s regulations don’t even hint at what NTU level disinfection might become a problem, but that might be because visibly dirty water – anything above about 5 NTUs – usually undergoes some sort of mechanical treatment before disinfection.
Where murky water is used for drinking, it is most often pretreated via settling ponds, coagulation or flocculation to remove sediments before disinfection. The turbidity is reduced because it makes bacteria in the water harder to kill.
And, of course, nobody wants to wash with, let along drink, water that appears dirty. Tap water in the U.S. is usually below 1 NTU. Water starts to look cloudy at 5 NTU, and at 25 NTU it gets murky.
The Kenai is pretty much always murky, and sometimes it looks worse. Looks matter here. They are at the heart of the turbidity issue on the Kenai.
The pristine north
“This goes back to when AK first developed the regulations,” Tabor said. The intent then was to keep Alaska’s clear waters clear. Clear waters are the most biologically productive. They are where little salmon start growing their way toward becoming big salmon.
Alaska had a bad history of dirty water, too. Dirty water from placer mining in territorial days into the early Statehood years in Alaska was linked to significant losses of fisheries habitat. Miners used water cannons to wash away the banks of some salmon streams in the search for gold. They walked dredges up others, ripping out the gravel as they went and leaving a muddy trail behind.
The results were not good.
“A 25 NTU increase in turbidity in shallow, clear-water systems may potentially reduce stream primary productivity by 13 to 50 percent or more, depending on stream depth and ambient water quality,” state biologist Denby Lloyd reported in a 1986 study. Lloyd was destined to go on to become a future commissioner of the Alaska Department of Fish and Game.
His study posited the appropriate question for the day: “What, then, are acceptable levels of human-induced turbidity in freshwater aquatic habitats that support fish and wildlife?”
His answer was that almost any increase in turbidity would lower fisheries productivity, but his study contained important caveats: “in shallow, clear-water systems…in freshwater habitats that support fish.”
The stretch of the Kenai under discussion as impaired has never been a “shallow, clear-water system,” and as a freshwater habitat for fish it is almost as marginal as the main stem of the Copper. It does not support large numbers of fish.
It is murky water through which salmon pass on their way to and from waters that support salmon.
Whether the water being more murky or less murky makes a difference to young salmon leaving the river or adult salmon returning is a question as to which no one has an answer. So, too, the question of how murky the lower river is naturally.
A two-way river
The DEC decided the lower river is impaired based on the difference in NTUs between a measuring station at river mile 23, just a few miles downstream from the Soldotna bridge, and a measuring station at mile 11.5.
The river bottom at mile 23 “is predominately gravel and cobble. The bank is comprised of poorly sorted cobble and gravel with minor amounts of sand and silt in the interstices,” according to 2008-2010 turbidity monitoring report prepared by the Kenai Watershed Forum.
At mile 11.5, the same report says, the river bed is “moderately sorted gravel overlain with well-sorted, fine-grained sand and silt. The depth of the sand and silt layer varies over the course of the season….A tidal influence is present at RM 11.5 and sites downstream of this location. During high tide the river water becomes backed up, resulting in slower water velocity and raised water levels. Reduced water velocity allows for the deposition of fine-grained silt.”
That silt build up only increases as one goes downstream to Cook Inlet. It is the reason the waters in and around the Kenai City Dock near river mile 1 comprise the dirtiest part of the river. The water is dirty even when the normal swarms of commercial and recreational fishing boats aren’t there to stir it up and make it dirtier.
There is no doubt boats stir up the silt. How much of that dirty water is picked up and pushed to river mile 11.5 on the incoming tides is an unknown.
It’s all about boats
The Watershed study was designed to buttress the argument that sport fishing boats using the lower river in July, when the king salmon fishery is at its peak, stir up the water and increase turbidity. Ricky Gease, the director of the Kenai Sportfishing Association, said that seems to be the heart of the discussion at hand.
Commercial fishermen in Kenai don’t much like to see tourists, be they from Atlanta or Anchorage, on the river catching fish. Commercial fishermen are a powerful interest gorup that would rather see the fish in their nets in the Inlet.
Gease and lots of other anglers see the turbidity study as largely a ploy to try to push people off the river.
The DEC backed studies, the Watershed report admits, were begun to examine the suspected belief “that human activity in the form of motorboat usage was a factor in elevated turbidity levels in the lower river.”
Only the role of boat activity in turbidity wasn’t suspected, it was obvious. Boats make the water slosh around. Sloshing water stirs silt. The water gets a little dirtier. A moose stomping around in the muck would do the same thing.
The question is whether it means anything at a fisheries habitat level or just at a written-rule level.
Cindy Gilder, a DEC staffer working on the issue, couldn’t answer that question, though she did provide a solid defense of the department’s conclusion that boat use on the river is the main factor affecting turbidity.
“When you look at the cycle of the tides and the boat traffic,” she said, “they don’t correlate.”
Whether there is any correlation with the heights of the tide and turbidity, or the volume of boat traffic downstream from mile 11.5 on the days of the worst turbidity upstream isn’t examined in the report, however.
But like some of the rest of the issues being discussed, it might not matter. The big question at the end of the day is a simple, philosophical one:
If water gets dirtier for a few days or weeks every summer and the salmon don’t notice, does it matter?