Las Vegas, known for its searing summertime heat and glitzy casino fountains, is projected to get even hotter in the coming years as climate change intensifies. As temperatures rise, water demand for the desert community is expected to spike. That is not good news in a fast-growing region that depends largely on a limited supply of water from an already drought-stressed Colorado River. Authorities are responding by aiming to wring more water savings out of everything from ice machines and grassy medians to industrial cooling towers, an aggressive conservation effort that could provide examples for communities throughout the Southwest.