Food comes from land worked worked using tractors designed and built by engineers in cities, in many cases harvesting crops geo-engineered by biologists and chemists in cities. And to the extent that one or more of these conditions isn't true, those are often premium products made possible by demand stemming from choosey consumers mostly living in... cities.
Also, as JoeAltmaier observed, very few people employed in rural areas are actually employed in agriculture. Furthermore, many of the subsidies that are provided to rural areas have nothing to do with -- and aren't necessary for -- agriculture.
Regarding water, rural areas contribute equally to water quality problems and in many cases make highly unsustainable use of water resources -- see California for example. Also, urban areas are often near plentiful fresh water sources anyways (see: Chicago).
The fantasy of farming as a self-sufficient profession disconnected from larger economic networks and holding a privileged place among society's disparate roles is one of the most insufferable aspects of rural culture imo.
Seems like a win-win, right? But, there are significant reasons why the rural areas would never accept that deal. They're addicted to the imbalance of power and urban subsidies.
They voted in an administration who wants to take away all of the subsidies for their poor population.
But they also voted in an administration who wants to massively subsidize their way of life at the expense of the rest of the tax base. Trump's basic economic plan is to use the carrot of access to America's rich suburban and urban markets as a mechanism for increasing domestic manufacturing (largely benefiting rural areas). So suburban and urban residents will be subsidizing artificial marketplaces that inflate the prices they themselves pay for goods.
His major governmental program will be a transportation infrastructure overhaul that will very likely disproportionately be paid for by suburban/rural areas and benefit rural areas.
And more importantly, those rural voters consistently vote for state governments that rob the tax bases of suburban and urban areas to pay for infrastructure that rural areas can't pay for on their own. Particularly for education and transportation infrastructure.
Basically, rural communities in the US are leeches who use their disproportionate access to political power in order to subsidize their unsustainable way of life on the dime of suburban and urban tax payers. And then have the audacity to claim the opposite.