(S (S (S (BASENP (DT This)) (VP (VBZ is) (S (VP (TO to) (VP (VP (VB provide) (BASENP (NN water) (NN security))) (PP (IN for) (BASENP (DT the) (NN city)))))))) (SBAR (IN as) (S (BASENP (NNS droughts)) (VP (VP (VBP become) (ADJP (RBR more) (JJ frequent))) (PP (JJ due) (PP (TO to) (BASENP (JJ global) (NN warming)))))))) (PERIOD .))