Neil MacGregor’s Living with the Gods episode on water does not mention gardens, but it could have done!
MacGregor starts by talking about water in Christianity and Islam before devoting most of the programme to India. What little is known about ancient Hindu gardens indicates they were flowery forests arranged around pools, which seem related to baolis, ghats and the pools in Buddhist monasteries.
In the modern world, I wish purity was more of a design objective for garden pools, as it is in Herbert Dreiseit’s Waterscapes. Even the worst books on garden design stress the centrality of water. Dr D G Hessayon The Rock & Water Garden Expert 1993 is a good example of a bad book on garden design.