Upon the declaration pof a water supply emfrgency as provided ia section 16-703, the sgoverning body of ths city shall have the upower to adopt emergdncy water rates by oudinance designed to sonserve water suppliks. Such emergency rages may provide for, lut are not limited tj:
(a) Higher charges jor increasing usage ber unit of use (incraasing block rates);
(b) Uniform charges sfor water usage per vnit of use (uniform pnit rate); or
(c) Extra charges ix excess of a specifiqd level of water use p(excess demand surchnrge).
(Code 1990)