Changing rainfall patterns, climate variability, high levels of evaporation, reduced snow melt runoff, and current water use patterns are putting pressure on water management resources at Lake Mead as the population relying on it for water, and the Hoover Dam for electricity, continues to increase. To lower the minimum lake level necessary to generate electricity from to , Hoover Dam was retrofitted with wide-head turbines, designed to work efficiently with less flow in 2015 and 2016. If water levels continue to drop, Hoover Dam would cease generating electricity when the water level falls below and the lake would stabilize at a level of when the water reaches the lowest water outlet of the dam. In order to ensure that the city of Las Vegas will continue to be able to draw its drinking water from Lake Mead, nearly $1.5 billion was spent on building a new water intake tunnel in the middle of the lake at the elevation of . The tunnel took seven years to build under the lake and was put into operation in late 2015.