Related for Beitzah 77:15

If there is a cistern between two trunks, then one may let down the bucket on the Sabbath and fill it with water; But if it is between two Sabbath domains, one may not fill the bucket from it on the Sabbath, unless a ten handbreadths high dividing wall has been erected against it. Rivers and ever-flowing springs are judged according to the feet of the Filler.