The problem with all surface springs these days is "Run off", not necessarily what comes out of the ground but what flows in from the ground.  You don't need a couple hundred yards for it to be an issue either because a couple inches will do it.  

There are two concerns with run off, one is biological and the other chemical.  What that means is to be safe we should both filter and treat the water before consumption.  Filter is to remove suspended solids based on size and treat to either neutralize or remove either or suspended solids or dissolved chemicals.  

Sounds complicated doesn't it?  Well yes it is.  I began my career treating water, first drinking water and waste water, then nuclear power plant boiler feed water.  You'd think that later one we wouldn't have to even think of but if we consider nuclear fall out as a possibility we do.  Heck someone who has a nasty mineral in their water does.  

What I can tell you is the best solution is always thinking of this in "Macro" and not rely on "One Size fits all" solutions.  I'll give you an example, almost every city water supply in this nation has different methods and standards for treating its water.  They all start in one place, which is why the guys are asking so many questions in this thread.  Its knowing you starting water quality and potential worse case.  On an open stream, any stream from a river to creek, that's normal dry weather to wet weather after a rain. Now its impractical to have a water laboratory for just in case so we should take a catch as much as we can approach.

The minimum I would recommend is a filter that is virus rated and has activated charcoal to remove most of the unwanted chemicals.  Now of course there's different ways to skin that cat.  Boiling, for example kills biologic just as adding antiseptic like iodine or chlorine and almost every refrigerator has an activated charcoal filter these days.  I'll let these guys recommend this brand vs that brand but will say there's some great inexpensive options available these days but encourage everyone not to ignore what you have on hand anyway because every option has a limited life.  For example, anyone with a modern refrigerator these days will tell you that filter does great but has to be replace in a matter of months.   Even high volume sources such as ceramics and membranes can only withstand so many cleanings.  We just had a very good thread on Berley filters and how to extend its cartridge life in storage.  

What that means to us in survival on this subject is what we must look at is time and that divided into short term solutions and long term solutions.  Surface water without constantly resupplying and monitoring like a city should always be considered a short term solution.  In some situation where resupply is not possible, we will run out of treatment methods in a matter of months not years.  That's why those of us who live in rural areas even if we have surface water have wells.  Funny as it is, probably the best tool we all have for a long term solution is a shovel.  The beauty of a well is once you cover it, run off no longer is an issue and whatever water quality we have, good or bad, will remain pretty consistent.  

I'm going to make a bold statement here which is going to be in contrast with today's norms.  I grew up drinking water from shallow stone lined wells and I'd rather have one of those that's fresh as it can be than a deep drilled well with chemicals leeching in.  That, of course, is dependent on where you live and what the geology is like and the best method to determining that is ask your neighbors because despite all our technological achievements, we still drill wells every day that ends up giving us water that's hell on wheels to make usable.  I miss those old shallow wells and often wonder we haven't made things worse.  Just yesterday my mom's neighbor asked if they could run a hose to fill his kids pool because his well water sucks so bad.  You typically don't have to deal as much with mineral deposits on a shallow wide well.  You do have to deal with rationing like in times of drought and the water table dropping.  Life and nature are a balance, solve one problem and you get another.  

This brings us to you don't need drinking water to flush a toilet or even take a bath.  During the aftermath of hurricane Alicia, my neighbors learned I had a flushing toilet.  I had a line outside my door until frustrated I went outside and told them "Look go haul your own water. There's a creek right there."  You would have thought they believed me a genius.  I probably should have added, if you gotta pee, there's a bush.  

Surface water is a very good thing to have.  All you have to do is understand its limitations.

Tj