River, lake and pond water potentially are a huge source of water, but unless you live in a very clean natural area on mountains chances are that is also very dangerous cause they easily are very polluted and poisonous when not full of bacterials like e.coli and similar in high concentration.
Potabilization of that water is an highly expensive thing for residential systems that cannot scale up like a municipal/provincial/national infrastructure, and unless it's really your only option to find water i feel to discourage you to use it expecially for drinking.
To potabilize it you will need a multistep filtering and sterilization system, and probably also a sedimentation tank where you will have to stock water and wait for long before move to the next step of filtering.
More, even if you start by test the water in a lab and setup an expensive filter to purify it, there is no guarantees that the polluttants will remain the same in time: industry and anything is on the water path before it reach your collecting point can eavily change what they throw in the same water, and you cannot really control it.
of course if you live in high quote on a mountain where there are glaciers and springs everywhere, chances are that the little torrent you would like to use as a source for you water is clean and potable.
In that case the steps to follow for potabilization and the hazards connected are [almost the same as the one you need to do with a wellpoint](/post/boreholes-and-wellpoints/)
## Laws and rules
Take care that is highly probable that you cannot harves water from a river/lake/ponds legally, the cumulative damage if everyone do that is too high and most nations have laws proibiting to use that water.
In South Africa you cannot take water from rivers nor lakes.
