What is a lake? Well, there's no good, agreed on definition. Most will agree that a lake is a body of water completely surrounded by land, but there are many other characteristics that hydrologists debate. How big should a lake be? Where is the line between a lake and a pond? A pond and a pool? And between a pool and a puddle? How deep should it be? When does a pond overgrown by a vegetation become a marsh?
Hydrologists agree that some of the boundaries are arbitrary. For example - different definitions of a minimum size for a lake range between one hectare and as much as 40 hectares in surface area. For our purposes - high altitude lakes - we need to choose and set the boundaries ourselves:
In order to put a lake/pool on a list we need good evidence that it really exists. Why do we bring up this topic? Well, the reason is that some high altitude lakes have been put on maps (even state-of-the-art maps) and they are not really there. We have experienced this ourselves in March 2012, when looking for Laguna del Muerto - a pool in the Ojos del Salado area at elevation of 5020m. We were using a map that was considered "THE map" by tour operators and guides working in the area. Still, after an hour or so combing the area with our noses glued to two Garmin handsets, we concluded that there was no pool there. Later on we have studied satellite photos and it seems that the lake simply dried out.
What constitutes good evidence? There is a saying: "Pics or it didn't happen". So, the best evidence will be a visual confirmation of the lake/pool existence. Pictures and videos taken when visiting an area are conclusive. Good quality aerial photos are also considered very good evidence. Next, we will also accept satellite photos, if they are of reasonably good quality. However, if resolution or quality is poor, it is possible to mistake another object - a glacier, a flat firn field or even a shadow of a cloud - for a lake. Google Earth is a good source of photos with reasonable quality. We will also accept climber's first-hand written reports, but we will always look for a visual confirmation.
Near-lakesBodies of water at high altitude are in continuums - of area, length, width and depth. Some of them may change their size dramatically during a year - they may be fed with molten snow in the wet season and then lose a large portion of their volume through evaporation in the summer. They may also freeze, and may not thaw for more than one year. When a lake is frozen for several years, is it still a lake that sometimes freezes, or rather a glacier that sometimes thaws? There are no good answers, and this is why we have set the above rules for a body of water to be qualified as a lake (or pool). However, there will be some bodies of water that 'almost' make it to be qualified - we'll call them near-lakes. They may be important for some reason, let's not lose sight of them. Examples of near-lakes: