Wildfire affect on high lakes

This is a great question. I sure don’t have any real answers. I could imagine a pulse of productivity getting washed into a lake after a fire. But I could imaging alternative scenarios, too.

I, too, am interested in the impact of the recent fires. Phantom Lake in the South Fork of the Tieton has fire go right above it with little or no impact that I could discern on the lake. I visited 3 Sombreros Lake in the Crow Creek drainage that was much more drastically burned up to by Norse Peak fire and could perceive little impact there, either. I’m eager to get further down into the Crow Creek drainage to Anna and Crescents Lakes and Hell Lake as well this summer. I was nervous about getting into the Norse Peak fire area only a year removed from the fire for fear of deadfall, and although common sense should be exercised, I’m less nervous. I’m under the impression that the Miriam Fire did not burn up to or over Hell Lake, but I’m eager to see it. Shouldn’t be much longer for the PCT to be snow free around White Pass.

I have been interested in this question for several years since my recent experience in the recent fires that raced through the Limebelt area of Okanogan county. I am very familiar with some of these lakes, after having provided fish many years ago at the request of prominent TrailBlazer George Lewis and his friendship with a restaurant owner at Ballard – I have been allowed access to some of these lakes ever since, to fish for “adequate” fish.
Last spring I fished one of those lakes after wading through ash to my knees on the access road, and fished several areas of the lake with no success whatsoever – my assessment was – NO FISH — that after fast fishing for a variety of sizes to 4 lb shortly before the fire. The lake has been stocked by a local private hatchery every year.
I have tentatively formed a hypothesis that the huge amount of ash that fell on the lake formed a layer of “caustic ash” otherwise known as LYE, that formed, and slowly descended to the bottom, thus killing any fish that came in contact with that lye layer by burning the gills instantly. I believe that same scenario could affect any lake under a fire.

Joshua, the lakes in the blast zone were ice covered when the mountain erupted. That saved the fish from the initial blast. There was a productivity spike as nutrients were washed into the lakes and for a while the fish grew larger. But I believe that in the lakes were the reproducing populations survived they have all settled back to their pre-blast stunted states.

I found this interesting article about wildfires and its effects on water chemistry.

The effects of wildfire on the water chemistry of dilute, acidic lakes in southern Norway

Summary

The most severe chemical conditions in wildfire affected surface waters occurred during some of the first post-fire rain events, but the amount of rain in relation to the hydrological status of the catchment prior to these events, and lake residence time, are decisive factors regarding when the most extreme water chemical conditions arise in surface waters affected by wildfire.

During the first post-fire hydrological episodes, strong acid anions as Cl− but primarily SO4 2−, are mobilized significantly faster from terrestrial to aquatic systems compared with base cations (ΣBC), which means that the acid neutralizing capacity (ANC) of lakes decline. For lakes with low pre-fire ANC values, significant drops in ANC down to very low negative values might occur, with subsequent increase in [H+] and toxic inorganic Al [Ali] to levels potentially harmful to aquatic life. In lakes with higher pre-fire ANC values, the drop in ANC during the first post-fire period is too small to cause severe acidification, and therefore harmless to aquatic life. Normal ANC values seem to be reestablished relatively fast in wildfire affected lakes, often within the first post-fire year.

After the extreme, post-fire water chemical peak, the main mobile anions (Cl− and SO4 2−) decreased faster than ΣBC. This combined with increase in TOC should imply a potential increase in ANC with time after fire in wildfire affected lakes. However, at the same time, the continuous dilution effect back to pre-fire levels, might counteract this potential ANC increase. This might explain why no ANC increase was seen in five of the six wildfire affected lakes, from one year after the fire and the next three post-fire years.

Increases in nutrients, N and P, and decreases in TOC in surface water during the initial post-fire period, followed by a gradual decrease in N and P and increase in TOC during the next post-fire years, have also been seen in surface waters from other wildfire impacted areas.

The water chemistry in the wildfire affected lakes in the Mykland area, had almost returned to pre-fire conditions 4.5 years after the wildfire. Thus, in this area of Norway, with significant reductions in acid deposition during the last decades, with [SO4*] reduction by 75–88 % in lakes from 1980 to 2011 (Schartau 2012), the most severe water chemical episodes, are again primarily driven by sea-salt events, directly linked to hydrologic episodes, directly as a result of heavy rain, or indirectly during snow melt as the sea-salt episode(s) are “accumulated” in the snowpack.

Hydrological regime, topography, geology, fire intensity, fraction of catchment burnt, lake morphometric conditions such as catchment-to-lake area ratio and lake residence time, are key factors for the variations in water chemical response in wildfire affected lakes.

• This reply was modified 5 years, 5 months ago by Rich OConnell.
• This reply was modified 5 years, 5 months ago by Rich OConnell.
• This reply was modified 5 years, 5 months ago by Rich OConnell.

Mt St Helens erupted in May 1980 – at that time Lily lake near White Pass would have been just opening from winter ice – or with some areas of continuing ice/snow on the surface. There are no known surveys of fishing success from 1980 – 1988, there were fishing efforts during that time, as the lake had previously provided large rainbows ( I viewed 3 RB over 3 lb one evening in 1953 at the Steilacoom Ice Arena, where a couple fishing friends came one evening to show off their catch; the lake had a reputation for good fishing. After the eruption Tb ‘s who fished the lake reported poor fishing and no evidence of survival of the 2 pre-eruption plants of Westslope Cutthroat. Since the Eastern Brook were successful prior to the eruption, but not seen in any numbers post-eruption I suggested that Jamie put the lake up for Eastern Brook again as I had a stock of EB at my NMFS Hatchery, from Tenas lake near Hoodsport, that had, in the past, provided large EB (4-5 lb) in that lake, and Nearby Price Lake; authorization was given, and that stock was replanted in Lily lake (records say Ford hatchery EB), so not clear, if original stock in Tenas was Ford??). So it appears that The eruption adversely affected Lily lake EB population (I know the trails in the area had from 8-12″ of ash on them). John Baskin did note that he saw a few fry when he made the replant in 1988 – so some survival of EB may have occurred after Eruption.