Many high tech industries have been attracted to areas such as Phoenix, Arizona, in turn bringing well-paid jobs.
Farmers are able to grow high value citrus crops due to the cheap availability of water for irrigation, therefore they are making a greater profit.
The increasing population of cities such as Tucson, Arizona mean a boom in the construction industry.
Tourism is a huge earner. Desert cities such as Las Vegas attract people from all over the USA and the world bringing money to the area.
Millions of people are attracted to water sports on the reservoirs and 700,000 people visit the Hoover Dam every year.
Industries such as aluminium mining in California rely on the water and the cheap power available from water control projects.
The huge cost of construction and maintenance is a financial burden to the states that funded the dams.
Silting of the reservoirs greatly reduces their capacity. It costs huge amounts of money to dredge the reservoirs so that capacity can be maintained.
Loss of silt downstream means that farmers now need to apply expensive fertilisers to land that was previously supplied with river deposits to keep it fertile.
High evaporation rates lead to increased salinity. This means that the HEP turbines have a shortened lifespan. The yield of crops decreases as the salinity of the land increases with evaporation bringing salts to the surface. The total cost of salination is estimated at $113 million a year.