This morning, the green lake looked different yet again.

If you remember yesterday’s pictures, we ended the evening with the lake being a fairly well mixed green color (picture on the right).

Now imagine my surprise when I came back in the morning and it looked like this:

The right side of the lake is still green, but the direct connection between inflow and outflow is an even brighter green! And the green inflow detaches once more at the tip of that little island (which it only did during the first observation yesterday, and two hours later the mixing had progressed around the tip).

There are only two ways I can think of how that could have happened:

a) During the night, there was a lot of un-dyed water added to the lake. Maybe through rainfall? But the effect would have been that the green color in the lake would have gotten diluted and, when the rain stopped, the inflowing water appears a lot greener than the surrounding lake water. Possible, even though I didn’t notice any rain during the night.

The other option is this:

b) Someone added more dye to the leaking pipes. This is the more probable explanation to me. The effect would be the same as above: A more intense inflow into a less intense lake.

In any case, the plume we are seeing now can only have been flowing with that intense a coloring into less green water for a couple of hours, otherwise the whole lake would have been mixed through and through.

I guess the easiest way to know which explanation is right would be (well, in addition to asking them directly) to have an objective measure of how green the water is, so that we would know if that changed over night or if the plume is really more intense now than yesterday. But with light that is always changing that is really not possible to say.

But this new green inflow is definitely beautiful: Look at the instabilities where it meets the stagnant lake water!

And more instabilities on the other side.

So those pictures were taken at around 7 in the morning. When I came back in the afternoon, the lake looked like this (sorry about the confusing lighting with the shadows and directly lit spots, can you ignore those and imagine what the color would look like under better light?):

Completely mixed and very very green! Interesting, isn’t it? So apparently the inflow stayed as intensely green as in the morning and, over the course of the day, mixed the whole thing.

P.S.: The company that puts the dye tracer in said on my Instagram @fascinocean_kiel that they are using uranine as dye, and that it’s completely safe for the environment. And, interestingly, that’s what we use in tank experiments under the name fluorescin, and that means that it is a fluorescent dye! I really need your UV light, Uta!! :-)