Sentence:  In view of the increasing shortage of usable surface and ground water in many parts of the Nation and the importance of finding new sources of supply to meet its present and future water <WSD>needs</WSD> , it is the policy of the Congress to provide for the development of practicable low-cost means for the large-scale production of water of a quality suitable for municipal , industrial , agricultural , and other beneficial consumptive uses from saline water , and for studies and research related thereto . 
Meaning of the word marked with <WSD> tags:  anything that is necessary but lacking