Is Oregon lake extremely pure water? If so, why?

Question

My question is,

Is the lake shown in the YouTube video Clear Lake, Oregon extremely pure water by volume not counting dissolved air which might be about 1 in 20 by volume?

In case you didn't realize, even pure water probably can absorb a significant fraction visible light even in the region with the lowest absorbtivity. I'm guessing that lake has essentially the same absorbtion spectrum in visible light as pure water and that you pretty much cannot see more than 200 meters through water at all based on my observation of that video. I guess it's technically correct to say it's extremely pure but is not extremely clear. Since pure water itself is not completely clear, I cannot tell for sure by observation that it doesn't have a solute with colour in it.

I believe the lake shown in the YouTube video Adventure Oregon - Lost Lake draining into a giant hole is the exact same lake. I don't know that so I will specify that I'm asking about the one in the YouTube video Clear Lake, Oregon even if it's a different lake. According to the YouTube video Adventure Oregon - Lost Lake draining into a giant hole, the lost lake of Oregon is a seasonal lake. If they are the exact same lake, could the purity be caused by the drain hole? If the drain hole really is in the lowest part of the lake, could the fact that water is constantly draining and getting replaced by rain water prevent and dirt from getting stirred up and lingering in the water? In the video with the full lake, there was also grass on the floor of the lake which is a sign that the lake might be a seasonal like and therefore might be the same lake as the one in the other video. Maybe also because of the drain hole, any slight bit of the type of moss suited for water dies off after the lake drains and its floor dries so there's no moss to break off microscopic fragments into the water and make it appear green.

Answer 1

The visibility or "clearness" is more a matter of suspended particulates, and organic material such as algae, than of dissolved material. For instance, runoff from glacial streams can be nearly opaque due to suspended rock flour, yet "pure" in the common sense of not having much in the way of algae &c. Conversely, some parts of the oceans can be very transparent due to lack of suspended sediment & organic matter, yet still have the same dissolved salts as other parts of the ocean.

Answer 2

Clear lake is clear for a number of reasons. One, most of the water flowing into the lake is from subsurface, so the water is coming up through sediments, i.e. filtered. Two it is the water supply area for Eugene Oregon, and therefore road and forestry activities are held to a higher standard, reducing the amount of sediment from runoff in the surrounding area. Three, the lake is very cold reducing algae or organic particulates in the water. Overall there is little in the way of inorganic particulate entering the lake and little opportunity for organic particulates to develop.

Wiki and the state forest service has some limited data on this lake:

Wiki

Forest Service Description

Answer 3

The lake is very clean and pure by the standards of some other lakes, but there are bound to be some harmless and beneficial impurities in there. The plants couldn't grow unless there was plenty of CO2 in the water, and it follows there is also oxygen. Nitrogen is dissolved from the air and nitrogen oxides are brought in by the rain. I would be very surprised if there were no calcium carbonate and other dissolved minerals in there.

The lake is fed by clear mountain streams and drains into an aquifer, so never becomes stagnant. If it were a seasonal lake and dry for part of the year, the abundant water weed couldn't grow. The water weeds help purify and oxygenate the water, and are a good sign. I would expect to find plenty of fish in there if there are not too many anglers taking them away. If you put a sample of the water under a microscope you would find plenty of mostly photosynthetic micro-organisms in it, but not enough to cloud the water to any significant extent. I doubt if it is the same lake you saw in the other video.

Answer 4

I believe the lake shown in the YouTube video Adventure Oregon - Lost Lake draining into a giant hole is the exact same lake.

That is incorrect, and that incorrect hypothesis resulted in a lot of incorrect reasoning. These are not the same lake. They are however close to one another. I apologize for being so harsh.

Lost Lake is a shallow, transient lake that disappears each summer. While it has no outlets above the ground, it has a number of outlets into the ground. The rock in the vicinity of Lost Lake (and also in the vicinity of the nearby Clear Lake) is very porous volcanic rock. A number of other lakes in the vicinity suffer the same fate as Lost Lake: They get lost in the summer.

Clear Lake, about 11 miles from Lost Lake by road, and about half that distance as the crow flies, does not suffer the same fate. Due to volcanic dams created a few thousand year ago, Clear Lake is much deeper than are the nearby Lost Lake, Fish Lake, and others. Clear Lake at 175 feet deep is a permanent, year-round lake. In fact, the underground waters from nearby sources such as Lost Lake and Fish Lake comprise the majority of the water flowing into Clear Lake.

Like those nearby lakes, Clear Lake also suffers a good amount of underground water loss. This is one of the key reasons that it wasn't artificially dammed. The leakiness is however more than compensated by the influx from the even leakier lakes such as Lost Lake and Fish Lake. The end result is that Clear Lake not only drains below ground, it also drains above ground to form the headwaters of the McKenzie River.

As to why Clear Lake is so clear, that's partly because it's fed primarily from underground sources that filter out most of the particulate matter before the water reaches the lake, and partly because the waters are so very cold. While life can survive at 40°F (4°C), it survives slowly.