I think the existing plant resources have way more flavor than just 10 different variations on "spring". These resources sound do-able, but not very interesting.
Also, gardens really don't produce more water; they suck them away.
One of the classic lines in Dune is about the townspeople looking at the date palms, and realizing that they each took up as much water as 20 men, and hoping that they would at least produce some fruit, but how this was in vain since they were out of season.
And there is other stuff about the massive luxury of the garden in the Governor's palace, and the popular resentment of it.
I would suggest; rather than making vanilla Food into water, make City Health into water.
So the limits to city growth are determined by both its food supply and its water supply. I think this makes a lot of sense; even without a big local water supply, you can substitute food for water by cutting back on city growth by using what water you have for people rather than agrictulture.
(Currently in developed countries, ~60% of water is used for agriculture, 35% for industry and only 5% by households - and most of that is for washing, and a little for cooking, not personal consumption. In developing countries I think its even higher for agriculture, and also higher for households)
Some ideas for this:
a) Take away the health bonuses from the various granary type buildings. Condense these buildings; there are too many of these anyway. Retool some of the other buildings that already give health so that it makes sense with them providing water. Many of them already make sense; you already have an aqueduct type building that gives a health bonus.
Don't have too many of these; currently health isn't often a binding constraint; food is much harder to come by.
b) Keep the current food resources, they have great flavor, but they just provide bonus tile yields (as some of them do already). You build a drip farm (or its upgrades)/soil enricher/complex on them.
These substitute for farm/pasture/plantation.
Drip farms and their upgrades are buildable anywhere. They provide 0 food on a normal tile, +1 with fresh water access, and a further +1 on a bonus resource.
Soil enricher and complex are buildable only on bonus resources, and also get a bonus +1 food for fresh water access.
c) Add in a few water resources from your list above that need to have a well or deep well built on top of them, that then provide a health resource to all your cities in the same way that rice/corn/etc. do in addition to improving tile yields.
You could replace some of the current health buildings with things like water-sellers market that gives a bonus health from these resources.
Deep well could be an improvement over normal wells with higher tech requirements that gives an extra tile output bonus, and/or also provides a local health bonus like forests do in vanilla.
I like the idea you have of multiple improvements that are better than previous ones; this gives workers something to do late game by rebuilding resources, rather than instantly getting an empire-wide uprgade from discovering a tech that gives +1 food to farms like in vanilla.
d) Have the windtrap tile improvement provide health to the nearby city in the same way that forests do +1 health per , in addition to a +2 food tile yield (improved by techs) and providing fresh water.
e) Various factories and such create unhealth because they require water to run, or because they pollute local water supplies.
You could also have Garden buildings that add happiness or commerce but provide negative health.
f) Then substitute Water (and the cool water drop icon you have above) everywhere that I said health.
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