The Unique Ecosystem of Las Vegas Wash Wetlands

Just a few miles off the Las Vegas Strip, lies an oasis in the middle of the desert, where the sound of slot machines and traffic is replaced by the sound of rushing water and birds; welcome to the Clark County Wetlands Park. 

Located on the east side of the Las Vegas Valley, the park extends along the Las Vegas Wash from the wastewater treatment plants to Lake Las Vegas (Las Vegas Bay).

Las Vegas Wash wetlands. (photo courtesy of Las Vegas Wash Coordination Committee)

Wetlands around the Wash are more than just a pretty oasis. The wetlands play an important role in filtering urban runoff and reclaimed wastewater of fertilizers, oil and chemicals, before it is discharged into Lake Mead. More importantly, the Las Vegas Wash wetlands create a unique habitat, hosting about 700 species of birds, mammals, reptiles and fish. 

The wetlands also function as a flood dam, controlling the erosion of the Wash. Like a big sponge, they absorb extra water from floods and gradually release them back into the river. Wetlands decrease erosion by binding the soil together. They also work as natural levees for banks by absorbing the impacts of fast moving water.

A variety of fish, which are both native and introduced species, inhabit the  Las Vegas Wash. A total of seven species including green sunfish, mosquitofish, common carp, black bullhead, red shiner, fathead minnow, and the suckermouth catfish were observed in the 2002-2003 fish surveys. However, none of the above mentioned species are native to Nevada. Non-fish species that were found during the surveys include the red swamp crayfish, spiny softshell turtle, bull frog and red eared slider. More than 200 species of birds have been found at the Wash among them are the Yuma clapper rail and Southwestern willow flycatcher. Some of the other species of animals that can be found in the Wash include the sidewinder, desert iguana, green sunfish, desert pocket mouse, hoary bat, Yuma myotis and Woodhouse's toad

Decline of wetlands

The wetlands started growing in size in the 1950s, when the first wastewater treatment facilities were opened and the Las Vegas Wash became a perennial stream. Until the 1980s, the growth of the city stimulated the expansion of the wetlands by introducing more reclaimed water into the channel. However, the increase of water flow, caused by the rapid urban growth in the 1980s, led to dramatic physical changes in the Wash. Erosion cut the channel deeper and wider, which caused the size of the wetlands to dwindle from 2,000 acres in the 1970s to less than 200 acres in the 1990s.

Erosion at the Las Vegas Wash. (Photo courtesy of Las Vegas Wash Coordination Committee)

Invasive species

Another issue that threatens the wellbeing of the Wash habitat is the expansion of invasive species such as Tamarisk (Salt Cedar) in the watershed. Tamarisks are resistant plants that take over the precious wetlands by displacing rival species. Non-native species spread quickly and alter the form and function of the wildlife habitat and nesting sites. These species are drinking up water supplies that are needed by the human and wildlife populations throughout the southwest. For example, a mature tamarisk can consume up to 200 gallons of water per day.

The wetlands also are subject to illegal uses such as hunting, dumping trash and uncontrolled vehicle operation.

 

Endangered species

Almost a dozen species in the Las Vegas wetlands are listed as endangered including the  Southwestern Willow Flycatcher, Razorback Sucker, Yuma Clapper Rail and Desert tortoise.

  

Southwestern Willow Flycatcher, Razorback Sucker, Yuma Clapper Rail and Desert tortoise are listed as endangered. (photo courtesy of Las Vegas Sun and LVWCC)

The loss of habitat, water pollution (mostly from agricultural runoff) and the invasion of non-native species threaten the existence of these animals.  The lateral erosion of the channel coupled with the construction of erosion control and bank stabilization structures have caused the habitat of these endangered species to be destroyed; however, once these structures are completed they will lead to long-term improvements of the wetlands.   

Changes in the chemistry and consistency of the flow components in the Wash (reclaimed water, urban runoff, shallow groundwater and stormwater) can acutely affect the fish and wildlife inhabitants. The fish in the Las Vegas Bay may appear healthy, but it is what is on inside that matters. Some fish in the bay and the Las Vegas Wash have mutated reproductive systems and different hormone levels than fish in other parts of the lake.

The treated water is altering the reproduction systems of fish in Lake Mead. (photo courtesy of Las Vegas Sun)

Restoration and management plans

The Las Vegas Wash Coordination Committee was formed in 1998 with the purpose of protecting and enhancing the Wash and the surrounding wetlands. The committee has contributed to the improvement of the wetlands and stabilization of the Wash’s banks through construction of erosion-control structures, planting trees and shrubs, management of invasive species and extensive wildlife, and water quality programs.

The sides of the Wash are being stabilized by planting native plants and installing flow-control structures such as dams and weirs. Weirs (low-height dams) along the Wash are permanent grade-control structures, designed to resist large storm events. They help reduce channel erosion by slowing down the flow of the water and providing a stable bed to grow vegetation. Weirs also improve the quality of the water by creating ponds that slow down the flow of water and catch excess sediment. Since the late 1990s, 13 flow-control weirs have been constructed in the Wash and three more are planned to be completed by the end of 2012.


There are controversial opinions about the impact of weirs on wetlands and wildlife habitat along the wash. Some believe that the construction of weirs can affect the fish inhabitants by impeding their upstream migration and by altering their habitat. However, it is apparent that wetlands improvement (as a result of weir construction) and vegetation enhancement activities contribute to a suitable habitat for fish and riparian species. The Las Vegas Wash Coordination Committee reports indicate the effectiveness of erosion control programs along the wash on the population of razorback sucker’s in Lake Mead. In fact, weirs have been affecting the spawning success of fish by providing a suitable environment (wetlands) and improving water quality.

Rainbow Gardens Weir, a grade control structure at the Las Vegas Wash

It is rarely expected to find an oasis of water, wildlife and vegetation in a desert valley, similar to the unique ecosystem of Las Vegas Wash. The Wash is home to many species of plants and wildlife that are not found anywhere else. The Las Vegas Wash ecosystem is also exceptional because it originated as a result of urban growth and human activities. The expansion of wetlands in the last fifty years is a measure of urban growth in Las Vegas, but at some point excessive urban growth has accompanied erosion, water pollution and wetlands degradation. Fortunately, the city is aware of the roles of wetlands in improving the environment and nesting wildlife and strives to save and enhance this precious ecosystem. Restoration and management plans, which were started in the 1990s, have brought a successful outcome and continue to restore the “urban river” ecosystem.