In the 1940s a British scientist by name of Beauchamp located a fixed sampling station for physicochemical parameters 5 km north-east of Nkhata Bay in the northern offshore waters of Lake Malawi. The lake is about 400 metres deep at that Beauchamp's sampling station, but no details were given on why that location was considered representative of the whole lake. I'm intending to do my sampling at that same location. However, as several years have lapsed after Beauchamp did his work and temporal changes may have occurred since then, and no clear reasons were given why that one location was considered representative I tend to hesitate. Could anyone help with a suggestion?
I would start with why test at all? What are you trying to confirm or understand? Then you can make logical choices about where to locate (but I would agree, one fixed spot seems like of limited use, so preferably increase or make mobile with rotation to various fixed points on a schedule).
the lake is quite big and it looks like there are several rivers feeding it. there is also a city near by, the influence of which can significantly modify your results if you will sample near Maleri island. If I would be you, I would sample at few locations and at different depth to see the differences with longitude.
is the lake closed? is there any feeding river or regular rain? so you may need to consider water add-on rate. And what is the purpose of the tests? try to think about locations where they are close to the uses of the lake (maybe water intake?!).
generally, you don't use one point. but i guess, he was doing a Q and D or quick and dirty. if i were to do it, you want an established point. doing it at the same point is better than starting at a new spot. perhaps its away from population..of around average depth.. and he thought it was representative of the lake..