KARACHI: President Arif Alvi on Sunday said that Karachi would need to install a desalination plant to meet the challenge of water scarcity. Speaking to the state-run APP, he added that the plant should have the capacity to treat 1,100 to 1,400 million gallons of water per day. He further said that, for the arrangement to be more feasible, an efficient tariff mechanism would also have to be introduced simultaneously. “A large investment is required with equal care towards revenue generation,” President Alvi said. “It should ensure that the essential commodity [water] is not only easily available to the citizens but also affordable for them,” he added.