The native flora does little to help the soil retain water.
During the intense rains of monsoon season or (relatively) wet months of January and February, a network of dry natural channels, called washes or arroyos, carved into the valley floor allows water to flow down from the mountains and converge in the Las Vegas Wash which runs through the Clark County Wetlands Park.
The wash system used to form a large natural wetlands which then flowed into the Colorado River, until the construction of Hoover Dam on the Colorado River led to the creation of Lake Mead.
Further development in the 1980s and 1990s made Lake Las Vegas, which required directing the Las Vegas Wash into tunnels which run under Lake Las Vegas and into Lake Mead.

Nevada receives an allocation 300,000 acre feet (370,000,000 m³) of water each year from Lake Mead, with credits for water it returns to the lake.
The allocations were made with the Colorado River Compact when Nevada had a much smaller population and very little agriculture.
The allocations were also made during a wet string of years, which overstated the available water in the entire watershed.
As a result, precipitation that is below normal for a few years can significantly affect the Colorado River reservoirs.
The Las Vegas area uses most of this allocation with Laughlin, Nevada using most of the remaining allocation.
In June 2007, the price of a cubic meter was 57 cents in Las Vegas.
Las Vegas gets around 90 percent of its water from Lake Mead.

Early Vegas depended on the aquifer which fed the flowing springs supporting the meadows that gave the area its name, but the pumping of water from these caused a large drop in the water levels and ground subsidence over wide areas of the valley.
Today, the aquifers are basically used to store water that is pumped from the lake during periods of low demand and pumped out during periods of high demand.
The native flora does little to help the soil retain water. During the intense rains of monsoon season or (relatively) wet months of January and February, a network of dry natural channels, called washes or arroyos, carved into the valley floor allows water to flow down from the mountains and converge in the Las Vegas Wash which runs through the Clark County Wetlands Park. The wash system used to form a large natural wetlands which then flowed into the Colorado River, until the construction of Hoover Dam on the Colorado River led to the creation of Lake Mead. Further development in the 1980s and 1990s made Lake Las Vegas, which required directing the Las Vegas Wash into tunnels which run under Lake Las Vegas and into Lake Mead.
Nevada receives an allocation 300,000 acre feet (370,000,000 m³) of water each year from Lake Mead, with credits for water it returns to the lake. The allocations were made with the Colorado River Compact when Nevada had a much smaller population and very little agriculture. The allocations were also made during a wet string of years, which overstated the available water in the entire watershed. As a result, precipitation that is below normal for a few years can significantly affect the Colorado River reservoirs. The Las Vegas area uses most of this allocation with Laughlin, Nevada using most of the remaining allocation. In June 2007, the price of a cubic meter was 57 cents in Las Vegas. Las Vegas gets around 90 percent of its water from Lake Mead.
Early Vegas depended on the aquifer which fed the flowing springs supporting the meadows that gave the area its name, but the pumping of water from these caused a large drop in the water levels and ground subsidence over wide areas of the valley. Today, the aquifers are basically used to store water that is pumped from the lake during periods of low demand and pumped out during periods of high demand.
Las Vegas Valley