Possible Clues:

• Deposit of rock holding usable water
• Way question's gripped retired judge - it holds water
• Well driller's target
• A lock closed early with some hesitation - it'll hold water
• Water-carrying layer of rock
• Water supplier, demanding almost a pound, starts to fill empty reservoirs
• Water-bearing layer
• Rock formation showing a peculiar style, mostly containing iron
• As the Welsh might say, like an aspen where there's water
• Ground water source