Hello Fanny IRM-ED and nevw,
Thanks for pointing out the untagged way, and for your questions.
The untagged way, and another one a little further north, is a vehicle track, like many others around the lake. I simply forgot to tag them. Both are now tagged and the tags uploaded.
The ESRI imagery shows the lake at about 60% capacity. The lake is a municipal reservoir. The local water authority pump from the lake all year round, and in dry years, down to 32% capacity, after which they then pump from Lake Julius, about 90km away.
The reason the tracks traverse the bottom of the lake is simple. The lake bed has a very low slope, and when the lake is pumped down towards it's lowest level, the area of the water shrinks considerably, the exposed lake bed drys out, and the tracks appear and are well used until the wet season, if there is sufficient rainfall to fill the lake again.
I've mapped the shoreline to what I estimate is the 80% mark, as that seems to be the most common level, until it is pumped down again.
I hope this makes sense.
Cheers,
Coco