A typical lake in Finland

I once heard in a pub quiz that the average depth of Finnish lakes is 7 metres. But I think that most lakes have never had their depth measured - and certainly not in the detail that I would want. So I decided to make my own measurements (using string, GPS and a boat) of a lake I spend a lot of time on. The original data comprised 121 depth measurements; the coastline was later refined using google maps.

The axes are just distances in metres (north upwards), and the depth is on the colourscale in metres.

Lakes in Finland

• In Finland there are over 180,000 lakes, pools, ponds of at least 500 square metres in surface area. 
• On a lake database (jarviwiki.fi) are included all lakes of at least 1 hectare in size (i.e. 100x100 metres is 10,000 square metres).
• There are lots of small lakes, and not so many bigs ones - following a power-law relationship, see chart below.