Sentence:  study methods for the recovery and marketing of commercially valuable byproducts resulting from the conversion of saline water ; and undertake <WSD>economic</WSD> studies and surveys to determine present and prospective costs of producing water for beneficial consumptive purposes in various parts of the United States by the leading saline water processes as compared with other standard methods . 
Meaning of the word marked with <WSD> tags:  of or relating to the science of economics