Easiest solution is IMO, 25 foot greenway (my made up term for uncultivated, unmowed, conserved land) on all tributaries, drainage ditches, and impoundments. Grasses, forbs, shrubs, tree's, and etc. soak up tonnes (just for you Phil) of water, and literally eat the ferts that would have run off into waterways. May be a bit of expense up front, but cheaper than taxes that last forever.
I know there are all kinds of objections to something like this. Just less expensive than paying forever.