Dear individual,

What you call run-off, the agribusinesses call irrigation.

Mr Opinion,
Run-off comes from built-up area not farms. Farms have soil/grass that absorbs water. Carparks, massive supermarkets, sporting facilties etc. have concrete that causes run-off !

I have long said we should build run-off collection ponds on city outskirts in the form of lakes, canal real estate & widening instead of narrowing river courses.

Dear individual,

I was being facetious, given that more than 80% of irrigation water is actually wasted.

http://www.ranops.net/news-and-interest/abfc-roebuck-bay-grounding.html

I wonder about the impact on reef & ocean of larger versions of such incidents !

In the days of Bradfield they would have had to use positive displacement pumps to push water up over the mountains, probably steam driven with lots of moving parts and wear and tear. These days an inline series of solar powered turbine type pumps along the route are available to run by remote control with virtually no maintenance. Its not a matter of getting bulk water inland, its need to get concentrated nutrient away from coastal waters.

It's dissolved nutrient pollution causing the damage, not silt, not oil or industry chemical pollution.