Drinking water has been scarce for over a decade in Taiz, but the problem has reached crisis levels in recent weeks as Iran-backed Houthi rebels besiege Yemen’s third-largest city in their escalating conflict with government forces. The needs of Taiz’s more than 1 million residents are now barely being met, humanitarian groups say, as access to wells is limited, desalination plants run low on fuel and water delivery trucks are largely prevented.