For what it is worth, the USDA-NRCS fences all animals out and then puts in pumps and pumps the water to the animals to drink because all the livestock you mention, poo a lot when they drink. It is a good management practice to consider, and if you have the money, it is a great thing to do. If not, I love your idea of riparian areas and limited access points.
I spent a fortune on what is known as a Comprehensive Nutrient Management Plan which is essentially a lot of scientific paper work based on what my sheep poo, what my soil types are, topography and a host of other data. It required bureaucracy in my humble opinion. Honestly, I think a great rule of thumb is this: since most ruminants poo 85% of what they eat back out in the form of manure, if you must import
feed onto the farm to sustain the numbers of animals you have, you are probably overloading your farm with too much manure run-off in the soil.
I am not saying their aren't ways around it without having low livestock numbers. If a
tractor is available, simply scraping up the manure from heavily used areas and piling it, ditches sending any rainwater into riparian areas will work. On large farms it is done all the time. But it is so refreshing to hear you are concerned about this right from the start. I am pretty impressed with your concern about nutrient conservation and management. Good for you!