There are about as many means of getting water on Gor as there are on Earth. Wells can be foud in the Tahari, aqueducts can be foud in Cities, spring water in the mountains and water can even be obtained from the Liana Vine.
“Another useful source of water is the liana vine. One makes the first cut high, over one's head, to keep the water from being withdrawn by contraction and surface adhesion up the vine. The second cut, made a foot or so from the ground, gives a vine tube which, drained, yields in the neighborhood of a liter of water.”
~ Explorers of Gor page 311