What I described is water filtration: biological filtration. Runoff from farms is organic in nature: manure and fertilizer, for the most part. Filtering it with traditional water filters (which need to be regularly replaced) is a huge waste of materials and a source of plastic waste that needs to be disposed of. It’s spending more money in order to fill up landfills needlessly.

Furthermore, it doesn’t even make sense from an infrastructure perspective. Artificial water filters are designed to be installed in pipelines. The water runoff on farms is not contained in a pipeline. It’s caused by rainfall and snowmelt on fields and running downhill (as well as sinking into the ground, soil permitting) over a large area. To filter it artificially you’d need to collect all that water into a pipe which would require enormous infrastructure to construct.

It’s so much easier, so much more economical, and so much more environmentally friendly to do minimal landscaping and allow water to collect in a basin located downhill where the water was flowing anyway. Some of it may need to be diverted for one reason or another, but that’s nothing compared to the cost of full collection and water treatment. Plus all those native wetlands plants that uptake the excess nutrients provide a habitat for native wetlands wildlife. It’s a win-win!