# Overview: Lower Colorado River Valley subregion
## Introduction:

The desert is seen by many as a dry, empty place. However, the biodiversity of the Lower Colorado River Valley encompasses much more than just sand and heat. Throughout this voyage, we will explore the unique geological structures that make up the Lower Colorado River Valley. We will see just how humans have utilized the land and water from the region, as well as the rich, cultural stories that have lived throughout the Lower Colorado River Valley for years. From Baja California to the Parker Dam, we will see the marvelous aspects of this region while focusing on the species, their habitats, and their stories. During this journey, themes will be presented including history and culture, geology and climate, biodiversity, and water and land use. Beginning with history and culture in Yuma, AZ, and ending with water and land use at the U.S./Mexico border wall, these themes will develop an awareness and understanding of sense of place within the Sonoran Desert. Just as this land is connected within itself, so are people connected to this land. Here in the Lower Colorado River Valley it is important to work hard to retain respect for this land, not only to sustain the earth but to sustain the communities living within it. Although many efforts are being made to preserve our ecosystem, there continues to be struggles in preservation. Diminishing levels of water in the Colorado River and immediate threats to wildlife and riparian areas such as the border wall are problems that have no current solution. If efforts are not immediately taken to resolve the detrimental issues addressed below, all the beauty and diversity the Sonoran Desert contains may be lost forever.

## A. History/Culture
### 1. Ocean-to-Ocean Bridge

The Ocean-to-Ocean bridge in Yuma, AZ, begins the journey toward discovering a sense of place in the Sonoran Desert. The Ocean-to-Ocean bridge is one of the most popular and well-known landmarks in Yuma, AZ. Yuma has a significant history and this bridge is one piece of that history.
Before dams were built all along the Colorado River, there was a significant river presence in Yuma. The river was much larger and harder to get across over most of the length of the river. The major exception to this was here in Yuma, AZ. What became known as the Yuma Crossing was the most tame and safest part of the river.
For a while, ferry boats would take people across the river from Arizona into California. However, in 1915 the Ocean-to-Ocean bridge was constructed and was the first bridge constructed over the Colorado River. Today, one can see the newly constructed bridge right next to the original bridge that was constructed in 1915. The bridge is now the focal point of Gateway Park, a park right on the bank of the Colorado where one can walk the trails through native trees and shrubs. While the Ocean-to-Ocean bridge is the gateway to Yuma's history and culture, the Yuma Territorial Prison is the foundation to what would become an important city in the southwest.

### 2. Yuma Territorial Prison

The next stop in Yuma, AZ, is another historical and culturally important landmark, the Yuma Territorial Prison. Overlooking the Colorado River, sits the ruins of this famous prison. Although it is no longer in use, it is a significant landmark and museum that cements it into Yuma's history and culture.
After the discovery of gold in California, many set out to head west. Since Yuma was located in the Colorado’s narrowest point in 1849, immigrants had to cross Yuma in order to arrive to the California gold fields. However, many were not fortunate enough to find gold in California and set out to find a new beginning. Travelers had already become familiar with Yuma during their journey, cementing it as a new home for many of them. It was seen as an oasis in the desert due to the presence of the mighty Colorado River. Travelers became comforted with the idea of finding water and escaping the dangers of freezing. By 1858, Yuma had experienced an economic boom and this surge in the economy lead to a rise in the population which helped establish Yuma County in 1871.
The Yuma Territorial Prison budget was around $25,000 and the prison was officially authorized by the legislature in 1875, it saw its first 7 inmates on July 1st, 1876. For 33 years the prison ran consecutively until overcrowding forced all prisoners to relocate to Florence, Arizona. Throughout the years, many facilities used this building for different reasons. For example, Yuma High School used it from 1910 to 1914 after their school burned down, earning them the name Yuma “criminals."
From 1939-1960, the location operated as both a museum and prison area after the locals raised funds in an effort to preserve this piece of history. The citizens were in favor of turning the territorial prison into a state park and the city board agreed to accept the funds in order to fulfill the citizens’ wishes. Later, land ownership disputes would end up delaying the park’s opening. Eventually, the city of Yuma sold the building for one dollar.
This prison holds a deep history for Yumans and is another manmade landmark that led to the development of the city as it is today. It has carried and contributed to much of Yuma’s history and culture. As the story of Yuma carries along, we see the prevalence of the Yuma Territorial Prison throughout it. It is a reminder of where Yuma came from and all that it has become since then.

### 3. MCAS Yuma

Our next stop in Yuma, AZ, is at the Marine Corps Air Station which was established in 1928. In 1948, the air base was built to train marines for World War II. The base became a flight school that taught multi-engine trainees, AT-6 engine trainees, and B-17 flying fortresses. After the war, the area was taken over by nature. The area remained this way until 1951 where the base was rebuilt and training resumed.
When cadets graduate, they are ready for assignments and combat training. During World War II, landing and flying fields were necessary and eight were built in Yuma as a result. In 1959, the Navy took over the base and Col. L. Davis became the first commanding officer. Today, the population of the base consists of 6,592 military, 5,531 family members, 2,651 civilians, and 5,000 transients.
MCAS Yuma is significant because of the number of people it has brought to Yuma, AZ. Not only has it brought many people to this city, it has diversified the population and created an ideal retirement location for veterans and their families. While this area is important to Yuma's history, it also has an environmental impact that is not always recognized.
The MCAS of Yuma covers about 3,000 acres in Yuma County. This area is home to many species, including the flat-tailed horned lizard which, although it did not get categorized as an endangered species until 2011, has been noted as "threatened" and as a "species of special concern" by the State of Arizona (Hollingsworth & Stepek, 2012). These classifications caused some organizations to mobilize their efforts to conduct surveys and collect data for population and environment analysis. One such survey was conducted by the cooperation and collaboration of the San Diego Natural History Museum, the Arizona Department of Game and Fish, and MCAS Yuma.
These studies focused on the numbers of flat-tailed horned lizards within nine-hectare for ten days, marking and recapturing the subjects. This study's goal was to provide information such as yearly survival, recruitment, and population growth. This survey averaged an estimation of 15 lizards by nine-hectare plot, which is a significant decrease from the Arizona Game and Fish Department's estimate of 76-77 adults per nine-hectare. However, the difference could be due to misreading subadults for adult populations. Studies such as these are important to highlight the species and diversity found within MCAS Yuma's land and will allow any issues or necessary actions regarding this species to be addressed.

### 4. West Wetlands Park

West Wetlands Park in Yuma, AZ, is the next stop through the journey of discovering a sense of place in the Sonoran Desert. For locals, West Wetlands Park has been an escape and a comfort, a place to enjoy a peaceful walk or to have a family picnic.
What was once a landfill is now a beautifully restored recreation area that has been divided into an "Upper" and "Lower" bench. The Upper Bench consists of roadways, playgrounds, a fishing pond, picnic ramadas, a hummingbird garden, and lighted pathways. On the other end, the focus of the development of the Lower Bench has been on restoring and preserving native trees, grasses, flowers, and shrubs and on building a riparian habitat.
Parks and recreation areas such as West Wetlands provide a home for native plants and animals to live and thrive since the development and growth of the city of Yuma over the years has altered the original state of the region. The designation of the Yuma Crossing National Heritage Area and restoration of important landmarks such as the Ocean-to-Ocean bridge has helped to preserve not only the environment, but also the history and culture of this area.

### 5. Imperial Sand Dunes

The Imperial Sand Dunes are a naturally occurring phenomena in the Sonoran Desert. These dunes are not only used for recreational sports such as motor cross but have also become a unique filming location for several major films including Star Wars: Return of the Jedi and Jumanji: The Next Level.
The Imperial Dunes are located about twenty miles outside of Yuma and extend for about 40 miles. This unique location typically welcomes one million visitors per year including those looking to take breathtaking photos of the dunes and of themselves in the dunes. Anyone who grew up in Yuma or around Imperial Valley knows about these dunes since many drove past them on their way to El Centro and San Diego.
When thinking about what sense of place in the Sonoran Desert means, its important to remember that places such as the dunes that we do not think of or see everyday are actually features of the Sonoran Desert that contribute to its overall beauty and magnificence. Another location that contributes to the magnificence of the Sonoran Desert is the Imperial National Wildlife Refuge where native riparian areas and wetlands are restored and protected.

## B. Geology/Climate
### 1. Estrella Mountains

The Sierra Estrella mountains are constantly sunny all year long. Due to the favorable weather, the mountains are best known for their outdoor activities. The natural terrain provides visitors with a picturesque background. Clear skies are conducive to stargazing events twice a year at the Estella Mountains Regional Park.
The northwest facing mountain consists of 38 km compact ridges and is 559 m above sea level near the junction of the Gila and Salt Rivers. Its highest peak elevation is 1,375 m (unnamed peaks) and the Montezuma Peak which is 1,323 m.
There have been recordings that multiple pits were filled with sandy sediment, this sediment is known as quartzofeldspathic sandstone. The Sierra Estrella rocks were likely uprooted by the detachment faults between 25 and 15 Ma. Over time, the rocks became deeply slanted in several areas by fluvial streams. Ultimately, the Estrella Mountains are just one of the many geologic formations within the Sonoran Desert. Another notable geologic feature are the Peninsular Ranges which are located from Southern California to the tip of the Baja California Peninsula.

### 2. Peninsular Ranges

The Peninsular Ranges would perhaps not be as prominent if the Baja California Peninsula did not form over the years through plate tectonics. The Baja California Peninsula was once part of the North American plate; however, the constant shifting of the plates that make up the earth cause landmasses to separate from each other, and this process often results in mountain ranges.
The Peninsular Ranges are a geographical feature stretching from Southern California to the tip of Baja California. The overall climate of the area surrounding the Peninsular Ranges is moderate year round, with cooler conditions higher up in the mountains. The rocks of these ranges are mostly Mesozoic granitic rocks.
There are other interesting geologic features within the Sonoran Desert that make it so unique. One such feature is the Pinacate Peaks, located south of the United States-Mexico border.

### 3. Pinacate Peaks

The Pinacate Peaks, located south of the United States-Mexico border, form part of a large volcanic field that is of great value to the Sonoran Desert's geology and climate. The Pinacate region contains at least ten volcanic craters, with the last volcanic activity occurring about 11,000 years ago. The region contains volcano types such as Pyroclastic cones, maars, and tuff rings. These surreal earth formations are an example of the versatility of landscapes found in the Sonoran Desert.
The climate can be described as arid with most rain pouring from convective storms, regardless of the season. The relatively large volumes of precipitation concentrated in small areas creates flash flooding, a crucial factor in geomorphic processes. This area has a range of temperatures from zero degrees Celsius (during rare winter freezes) and over fifty degrees Celsius. In earlier years, people avoided the area because its warm climate and ground would reduce vegetation.
The formation of these features in the land have been a subject of study for many years. There are a significant number of people who want to explore and identify all the geologic formations that have created this landscape.

### 4. Gran Desierto de Altar

The Gran Desierto de Altar is located in Sonora, Mexico. It covers approximately 5,700 square kilometers and is one of the major sub-ecoregions of the Sonoran Desert. Although most of it is in Sonora, Mexico, the gran Desierto de Altar extends across the broder into Organ Pipe Cactus National Monument and Cabeza Prieta National Wildlife Refuge.
Being North America’s largest field of active sand dunes, the Gran Desierto de Altar is home to various types of dunes, the tallest standing 200 meters tall. Here, linear, crescent-shaped (barchans), and star shaped dunes can be found. These can be categorized as simple, compound or complex, depending on seasonal changes in the direction and strength of the wind. Crescent-shaped complex dunes and star-shaped dunes are a rare type of sand dune that only exist in certain locations around the world. These dunes can reach as high as 200 meters high and can occur both singly and in long ridges up to 48 kilometers in length.
The sand needed to form and maintain these dunes come from the fluvial and deltaic sediments of the Colorado River delta, the beaches of the Sea of Cortez, the River Sonoyta, and the smaller river and stream fans formed in those parts of the reserve where there are volcanic and granitic mountains.
The geological history of the Gran Desierto is intimately linked to the opening of the Sea of Cortez and the capture of the ancestral Colorado River. Prior to the opening of the Sea of Cortez, vast amounts of sediment accumulated in this region brought by rivers of which little trace remains today. The creation of the Sea of Cortez shortened the rivers and increased their average gradient, causing them to cut into the pre-existing landscape leaving behind river terraces, remnants of the former higher level floodplains.

### 5. Puerto Peñasco

Located near the Pinacate Biosphere Reserve, sits the famously known, Puerto Penasco, also commonly known as Rocky Point. As is its name, Rocky Point is surrounded by extensive mountain ranges and shares many of its geological characteristics with that of the Pinacate Biosphere Reserve. Such characteristics include the remnants of ancient volcanoes that can be found on the beaches of Puerto Penasco and inactive volcano peaks that can be seen throughout the entire state. These mountains, along with the two nearby islands, create a barrier for the region that prevent extreme weather events from happening, however, do not make it impossible. Due to phenomena, El Nino, Puerto Penasco still experiences tropical storms and hurricanes that reach the northern Sea of Cortez. Such disasters are rare but cause significant damages when they occur.
Rocky Point is known for its warm weather temperatures. During the summer, Puerto Penasco experiences hot and humid climates while in the winter it exhibits itself to be cold and dry. Temperatures range from 109°F in the summer to 51.8°F in the winter. This generally good weather brings many tourists during late May to late June. The hot season starts from June 14 to October 4 averaging at about 89 degrees Fahrenheit. The cooler season starts on November 27 and ends March 8 averaging below 73 degrees Fahrenheit.
Its temperatures are highly influenced by the nearby Sea of Cortez. The Sea of Cortez experiences very warm water temperatures, ranging from 75°F in the summer to 61°F in the winter. This direct influence also contributes to the rainfall of Puerto Penasco. Puerto Penasco is located on the northwest fringe of the North American Monsoon 6 circulation pattern, which in turn, causes Puerto Penasco to experience substantial seasonality in precipitation, specifically in July and August. These summer monsoon rains come from the Sea of Cortez, often in masses of water-laden air called “Gulf Surges.” However, annual precipitation is minimal due to its location in the rain shadow of the mountains of northern Mexico’s Baja California peninsula.

## C. Biodiversity
### 1. Telegraph Pass Trail

Telegraph Pass has become a wide attraction for anyone in Yuma, Arizona. Its 5.3 mile trail provides unique scenery from which it has gained its popularity. Along the way, people are able to enjoy the various wildlife that the desert of Yuma has to offer, from its native cacti to its reptilian friends, the biodiversity within the Telegraph Pass Trail is a representation of Yuma County.
The plants and animals that are located here are similar to those that are located within Yuma County. Throughout the trail, the scenery provides a variety of floras, from cacti, to shrubs, to trees. These varieties of plants include shrubs such as brittle brush, ocotillo, creosote bush, trees such as the Ironwood and Palo Verde tree, and cacti such as the saguaro and beavertail cactus. The trail is also home to wildlife that is native to Yuma. For example, you may encounter the western diamondback rattlesnake, chuckwallas, desert horned lizards, roadrunners, coyotes, the black-throated sparrow bird, and so forth.
The trail's warm weather conditions allow for such wildlife to flourish along the path. It provides the appropriate circumstances for these species to inhabit the area and satisfy their needs. The Telegraph Pass Trail has become the place for species to live and for the community to learn about the astonishing wildlife that exists within this area.

### 2. Kofa Wildlife Refuge

Heading out of Yuma up Highway 95, there is a large wildlife refuge, the Kofa National Wildlife Refuge. The refuge was established in 1939 and encompasses over 665,400 acres of the Yuma Desert region of the Sonoran Desert. The refuge is currently home to a diverse range of wildlife and plants.
Some of the notable plant species within the Kofa Wildlife Refuge include the saguaro cactus, prickly pear, cholla, hedgehog, pincushion, and barrel cacti. Within the refuge in Palm Canyon, California palms are dispersed throughout and continue to thrive even though they used to live under much wetter and cooler conditions.
There are quite a few animal species that make this part of the Sonoran Desert their home. These include badgers, foxes, ground squirrels, pocket mice, and kangaroo rats. However, their are many mammals, reptiles and amphibians, and birds who call the Kofa Wildlife Refuge their home. Mammals such as the ringtail and mountain lion, bighorn sheep and mule deer, and bats each have found places in the desert to call home. Amphibians and reptiles including the Gila monster, the western diamondback rattlesnake, chuckwalla, desert horned lizard, desert iguana, and the red spotted toad have also found sanctuary in this wildlife refuge. Birds including white-winged doves, cactus wrens, northern flickers, canyon towhees, phainopeplas, Gambel's quails, turkey vultures, and golden eagles thrive in their desert oasis, some through the protection of the largest saguaro cacti.
Although many believe that the Sonoran Desert is desolate and void of life, plenty of wildlife and flora and fauna are dependent on it for their survival; in turn, they populate it with beauty and life. A little over one hundred miles to the west, the Imperial Sand Dunes cut through the desert and bring a uniqueness and landscape that cannot be matched anywhere else in the United States.

### 3. Imperial National Wildlife Refuge

The Imperial National Wildlife Refuge is located 30 miles from the Colorado River where it divides in two. This refuge offers resources to help restore native riparian habitats as well as wetlands in order to help migratory birds and other species. These riparian zones are important because they recharge groundwater, store floodwater, and aid in water quality. Ultimately, these zones provide a biodiversity hotspot for plants and wildlife.
During the spring and fall the greatest variety of birds can be observed at the refugee. Some year-around birds that are observed include the ladder-backed/Gila woodpeckers, Verdin, Crissal Thrasher, and Abert’s Towhee. The size of this location is 49.3 square miles, 31,558 acres. In total, over 275 different species have been noted at the refuge.
Other species that are part of the conservation status and use the habitat within this location include the sandhill crane and willow flycatchers. During the winter, Canada geese, tundra swan, and bald eagle. Some conservation concerns are the loss of cottonwood, willow, and marshlands resulting in the loss of habitats. In order to combat this, projects are being implemented to restore the riparian areas. While it is important to protect riparian areas such as the Imperial National Wildlife Refuge, it is equally important to protect our water, including the Salton Sea and rivers such as the Colorado.

### 4. Anza-Borrego Desert Park

A few miles west of the Salton Sea, the Anza-Borrego Desert Park provides a home to many flora, fauna, and wildlife. The Anza-Borrego Desert Park is known for its beautiful wildflowers that bloom every year during the spring and early summer. The blooming starts in late February in the lowest part of the region and moves towards higher land in May. Flowers tend to grow everywhere except sandy regions, rocky hillsides, high mountains, and badlands. The plants are grouped into four primary groups: agave and yuccas, bushes, cacti, and wildflowers. Due to the lack of rainfall in this region, especially within the past year, the length of time the flowers are in bloom has been significantly shorter. Additionally, increasing temperatures are affecting these plants negatively.
The Anza-Borrego Desert Park is also home to many species of animals. One of these popular species includes the peninsular bighorn sheep. Listed as an endangered animal in 1998, this species mainly resides in low elevation areas that are dry and rocky. In order to prevent the animals from being disturbed, the park closes areas--such as Coyote Creek--to vehicles from June to October. Closing designated areas to vehicle traffic allows the sheep to navigate the land to find watering areas. Since these sheep are an endangered species, it is also important to consistently verify the population levels; therefore, the sheep are counted and monitored frequently to ensure the population is not decreasing.
Another distinctive animal to the Anza-Borrego Desert Park is the deer mule. Unlike the bighorn sheep, deer mules are mostly located in higher elevations. These mammals tend not to stray far from a water source and they generally hunt at dawn or dusk. Mountain lions, bobcats, and coyotes are the natural predator of the deer mule; in fact, one sound that is heard very often in this region is the yelping of coyotes. Other animals that can be found in this park include the desert kit fox, black-tailed jackrabbit, desert cottontail, antelope squirrel, and the kangaroo rat.
Unfortunately for this beautiful park and its wildlife, the Salton Sea may have a negative impact on it. This park is very close to the Salton Sea, almost as close as the nearby cities of Brawley and El Centro. As the Salton Sea dries up, the lake beds, or "playa," become more and more exposed and the salty playa becomes wind-borne. This wind-borne dust has created dangerous air quality for the people who live in this area and the wildlife that find solace in parks such as the Anza-Borrego.

### 5. El Pinacate y Gran Desierto de Altar Biosphere Reserve

El Pinacate and Gran Desierto de Altar Biosphere Reserve is home to a wide variety of diverse mosaic habitats and animals. It is a combination of volcanic landscapes, which are locate within El Pinacate, and sand dunes, which are located in the Gran Desierto de Altar.
Many species are endemic to the Sonoran Desert. They feature sophisticated physiological and behavioral adaptations to the extreme environmental conditions. For example, this can be seen through the Pronghorn’s ability to feed on thorny cactus species or the extremely long seed dormancy of most plants. It currently holds 560 species of vascular plants, including an endemic plant restricted to the volcanic shield. This would include, for example, the sculptural elephant tree.
The reserve is home to more than 540 species of vascular plants, 44 mammals, over 200 birds, more than 40 reptiles, as well as several amphibians and even two endemic species of freshwater fish. The biosphere reserve is home to animals such as the Sonoran pronghorn, the bighorn sheep, the mule deer, the gray fox, the Gila monster, and the desert tortoise. The reserve also exhibits large caves in which the migratory lesser long nosed bat resides in. The name of the reserve itself comes from the name of the desert stink beetles showing just how important its biodiversity is to the area.
Such richness in biodiversity comes from the unusual freshwater regime located within the reserve. The minimal precipitation it receives favors the permanent water availability in what are called “tinajas.” Some of the tinajas contain water year round which serves as a crucial resource for wildlife year round.

### 6. Organ Pipe Cactus Reserve

One of the first images that comes to mind when a desert is mentioned is tall, green cacti. The Organ Pipe Cactus International Biosphere Reserve is of great importance to the biodiversity of the Lower Colorado River Valley region and the Sonoran Desert as a whole. This reserve contains various species of wildflowers, trees, shrubs, and other essential animals. These elements culminate in a space that hosts magnificent forms of life and diversity.
Some of the species that make up the biodiversity include the Palmer Indian mallow, Rayless golden head, and desert agave, among other wildflowers. Various trees and shrubs are also evident in this reserve including creosote, brittle-bush, jojoba, palo verde, and cacti towering high above.
The Quitobaquito Springs and pond is a significant body of water within the Organ Pipe Cactus Reserve and it holds cultural significance and historical relevance. The challenges presented to the pupfish and its habitat have led to the current protection and tracking of this species and its environment. After monitoring these species, there was a noticeable decrease in its population of about four times its population numbers between 1975 and 1981. In 1993, some growth was observed, and new monitoring and managing procedures continue to take place to preserve this species. One of the current threats to the Quitobaquito Springs is the U.S./Mexico border wall. Construction was heavily increased between 2016 and 2019 and this construction has had an immediate impact on bird populations here. In fact, the disappearance of 47 different bird species, including some endangered species has been documented by ecologists. Manmade structures such as the border wall almost always have negative impacts on wildlife, water, and the land in general.

## D. Water/Land Use
### 1. "El Rio" Local Gathering Spot

Our next stop on this journey takes us across the U.S./Mexico border and into San Luis Rio Colorado Sonora. "El Rio" is the standard way for locals to refer to the area directly under the Mexican Federal Highway 2, which connects transit from San Luis Rio Colorado and Mexicali.
Since the early 1900s, the Colorado River has been completely or nearly completely drained for irrigation. The once formidable Colorado River is usually dry or forms a small stream in this area: An excerpt from Water is for Fighting Over, and Other Myths About Water in the West states: "...it is not just San Luis, it is San Luis Rio Colorado. It is the only city that has the name Rio Colorado, Campa, technical director of the city's water utility, told me as we strolled the river's sandy bottom on a warm spring morning. It took imagination to grasp at what Campa was getting at. Nineteenth century steamboats once passed this spot. The Colorado was once a river here. No more. The only thing capable of navigating the Rio Colorado's bed that day was a four-wheeler with fat tires" (2019).
This description accurately depicts what the Colorado River looks like the majority of the time. What was once a free-flowing, mighty river, is now barely a stream. It is a completely different space due to the increased number of people on the weekends, whether the zone is dry or some water is released. Whoever visits the area is likely to partake in activities such as racing and drinking, among others. Many people think of these activities as a way of taking the name given to their city and making it their own, they are creating memories that will link them to this place permanently.
Locals have many different ways of interpreting what "El Rio" means to them. Some hold on to the history that it represents, such as the formation of the city. While others prefer to redefine what "El Rio" means to them by creating new traditions and memories with this piece of land.

### 2. Salton Sea

As part of the Colorado River Delta, the Salton Sea stands as the largest lake in California. It is located in the southern riverside and the northern imperial counties in southern California. Throughout history, the Salton Sea has regularly filled and dried out due to its elevation level. However, the most recent version of the Salton Sea was formed when the Colorado River floodwater breached an irrigation canal being constructed in Imperial Valley in 1905 this water flowed freely into the Salton Basin for 18 months. The sea has since been maintained by agricultural runoff from the Imperial and Coachella valleys. Today, the Salton Sea functions both as a sump for agricultural runoff and as an important wildlife area.
The nutrient-rich runoff includes a high volume of salt and helps support a vibrant aquatic community, home to fish and wildlife. In the past, the Salton Sea also was a popular spot for recreational boating and fishing. At one time, the Colorado River Delta’s wetlands and riparian habitat spanned nearly 2 million acres and stretched from the northern tip of the Gulf of California to Southern California’s Salton Sea, providing rich habitat for more than 200 plant species, countless fish, hundreds of species of migratory birds and waterfowl, and wildlife such as deer, quail, raccoons, bobcats, and even jaguars.
Due to the significant loss of wetlands in California and other areas, the Salton Sea ecosystem has become one of the most important wetlands for many species of migratory birds and supports some of the highest levels of avian biodiversity in the southwestern United States. The Salton Sea’s National Wildlife Refuge has over 380 species of birds, among the highest totals of all national refuges. The Salton Sea provides an important habitat for several endangered species including the desert pupfish, Yuma clapper rail, and the brown pelican.
Despite the Salton Sea's importance for many species, including endangered species, the Salton Sea has recently faced many complications. Due to its formation as a landlocked body of water and its continued contamination of agricultural runoff, the Salton Sea has become toxic to not only the wildlife, but also human beings. With the sea already saltier then the Pacific Ocean, salt continues to build up. Reduced water supply, minimal rainfall, and evaporation have also significantly lowered the water levels in the already quite shallow Salton Sea. Not only have such situations placed a risk to the wildlife habitat, but have also affected nearby communities. Exposed lake beds, known as the “playa,” have led to serious issues with the local air quality. The sandy substance holds a century’s worth of agricultural runoff.
Unfortunately, the environmental problems of the Salton Sea have expanded further than just the local region. It is no longer affecting only the community around it since wind-born dust has spread the poor air quality to many parts of Southern California, into Arizona, and even to nearby parks such as the Anza-Borrego Desert Park. With the Salton Sea receding, the “playa” only gets larger, releasing more contaminated particles into the air. This situation is causing air pollution and poor quality of life for the the wildlife and people it used to support.

### 3. Parker Dam

Our next stop in our tour of the Sonoran Desert is an important one that pertains to water use. The Parker Dam is about 155 miles downstream of the Hoover Dam and is important because it brings water and power to the residents of the Lower Colorado River Valley. The main purpose of this dam is to store water and eventually pump it to the Central Arizona Project Aqueducts. The Central Arizona Project delivers 488 billion gallons of water from the Colorado River out to communities, agriculture, and wildlife use.
Funded by the Metropolitan Water District of Southern California, the Parker Dam helps deliver water to the Los Angeles and San Diego area. Without this water source, these places would not thrive and grow in population. Parker Dam is the deepest dam in the world it is no surprise that it is able to pump large amounts of water that supports one of the most populated places on earth.
Housing four hydroelectric generating unit, the Parker Power plants can produce about 30,000 kilowatts per unit and these units are non-polluting. Around 50% of the power output is used for the pumping of water through the aqueducts. The other 50% is promoted by the Western Area Power Administration.
The Parker Dam is often recognized as one of the greatest uses of water in Arizona especially because it provides water to so many people and utilizes hydropower to generate electricity. However, this is just one perspective on the Parker Dam. A more pessimistic but realistic perspective recognizes that the dam disrupts the natural flow of the Colorado River and is used to transport water to states that are miles away from the Colorado River. While hydropower is a great renewable source of energy, water is not so renewable. The more we use our water, the more we will experience long periods of drought, and the more the climate will change, and not for the better.

### 4. Lake Havasu

According to Lake Havasu’s 2020 water conservation plan, the land uses within the city are residential, commercial, industrial, recreational, resort, and underdeveloped. Residential land is scattered throughout the city while commercial and industrial are condensed parallel to main traffic routes. Residential and resorts are located throughout the shoreline and island. Four detailed plans have been set in place to address future growth patterns of this region.
The city’s main water source comes from the Colorado River. Lake Havasu City has 4th priority Colorado River water entitlement that totals 28,581.7 acre-feet/year. Around 3,500 ac-ft are withheld for future Native American water use. Lake Havasu continues to secure thousands of acre-feet within other subcontracts.
In order to lower the city's allocation request, the city plans to practice the reuse of wastewater for landscape and land irrigation. All water passes a 48-inch pipeline to go to the city's water treatment plant. The water is eventually treated with ferric chloride where it then goes through sand filter processes containing a bacteria and ultraviolet radiant system to disinfect the water.
While many images of Lake Havasu portray summer vacations full of jet skis and family boats, the reality of Lake Havasu is not as bright. Lake Havasu faces many of the same difficulties as Parker Dam because it is also connected to the Colorado River. Water levels continue to decrease as more and more water is used for agriculture in Arizona and California and for ornamental grass in suburbs. Even with the wastewater treatment plans, it may be too little too late unless heavy restrictions are placed on what the Colorado River water can or cannot be used for.

### 5. Palo Verde Nuclear Generating Station

The Palo Verde plant treats millions of gallons of wastewater. The plant plans to extend this treatment to the Buckeye groundwater to reduce the amount of waste. Buckeye's water is high in mineral and salt content, making it difficult for the general public to use. In using these sources that other facilities do not use, wastewater would be reduced by twenty percent.
Palo Verde is located about one hour's drive west of Phoenix. It is the largest nuclear generating station in the country. According to the plant manager, Rick Lange, the plant uses about 40,000 gallons of water every minute in the winter. On the other hand, the plant uses about 60,000 gallons of water every minute in the summer. The waste water the plant plans to utilize will aid habitat restoration.
In the future, the station will treat even dirtier water and has found the funds for these plans. Currently, the station is working to get approval from the state and farmers near the area. Additionally, new cooling technology has been developed to work on different water options.

### 6. U.S./Mexico Border Wall

Circling back around to where we started this journey in Yuma, AZ, we arrive at the border wall between the United States and Mexico. The border wall establishes the international boundary between the U.S. and Mexico and has been present in most of the area for many years. However, in the past four years, border wall construction has increased tremendously, affecting much of the land in which it is found. Additionally, much of the water around the area has contributed to the construction of the border wall. The Arizona portion of the wall alone required approximately 50 million gallons of water to complete. This water is used for dust control purposes as well as in making concrete bases to hold the towering steel slats. The border wall has brought many concerns in regard to the degradation of the surrounding land. Environmental impacts such as erosion, soil compaction, ecosystem fragmentation, and flooding have been under crucial observation.
The U.S./Mexico border wall has demonstrated itself to have a negative impact on the environment. The area in which the border wall is located is considered one of the most ecologically diverse wildlife migration corridors in all of North America. More than 450 rare species live in these areas, many of which cannot be found anywhere else in the world. However, through its establishment and construction, the border wall has destroyed much of the land's wildlife habitats. At least 700 neotropical birds, mammals, and insects migrate through the borderlands each year. This however, has been limited due to the continued construction of the U.S./Mexico border wall. Ultimately, the wall has inhibited the movement of wildlife, reducing their ability to navigate towards food and water.
The border wall not only inhibits animals from navigating to areas within their habitat, but also causes species to abandon their habitats, specifically in the Quitobaquito Springs within the Organ Pipe Cactus National Monument in southern Arizona. The enhanced construction of the border wall within the past four years has come within 120 feet of the Quitobaquito Springs and has resulted in the disappearance of about 47 species of birds, including some endangered species such as the willow flycatcher. The U.S./Mexico border wall has many implications politically and culturally, but just as important, if not more so, are the implications it has on the environment in all aspects.
* ↑ Flashback Friday: The Day Yuma's Ocean-to-Ocean Bridge opened to traffic. (n.d.). Retrieved April 06, 2021, from https://azdot.gov/adot-blog/flashback-friday-day-yumas-ocean-ocean-bridge-opened-traffic
* ↑ Ocean to Ocean Bridge – connecting a Cross-Country Highway. (2020, August 11). Retrieved April 06, 2021, from https://photobyjohnbo.wordpress.com/2020/08/18/ocean-to-ocean-bridge/
* ↑ Park History. (n.d.). Retrieved April 06, 2021, from https://azstateparks.com/yuma-territorial/about-the-prison/park-history
* ↑ Hollingsworth, B. D., & Stepek, M. A. (2012). FLAT-TAILED HORNED LIZARD (Phrynosoma mcallii) SURVEYS ON MARINE CORPS AIR STATION YUMA, ARIZONA.
* ↑ MCAS Yuma In-depth Overview. Military Installations. (n.d.). https://installations.militaryonesource.mil/in-depth-overview/mcas-yuma.
* ↑ MCAS historic overview. Living in Yuma, Arizona. (2018, March 2). http://southwestlivingyuma.yumawebteam.com/unique-to-yuma/mcas-historic-overview/.
* ↑ Visit Yuma. (n.d.). Retrieved April 06, 2021, from https://www.visityuma.com/about-yuma/history/
* ↑ Yuma West Wetlands. (n.d.). Retrieved April 06, 2021, from https://www.yumaheritage.com/west-wetlands.html
* ↑ Imperial Sand Dunes National Recreation Area. (n.d.). Retrieved April 06, 2021, from https://www.visityuma.com/things-to-do/imperial-sand-dunes/
* ↑ Melchiorre, E. B. (1992, September). Geowgy and Mineral Resources of the Sierra Estrella, Maricopa County, Arizona. http://repository.azgs.az.gov/sites/default/files/dlio/files/2010/u14/ofr-92-15_report_sierraestrella.pdf.
* ↑ Mueller, K., Kier, G., Rockwell, T., & Jones, C. H. (2009). Quaternary rift flank uplift of the Peninsular Ranges in Baja and southern California by removal of mantle lithosphere. Tectonics, 28(5).
* ↑ Langeheim, V. E., & Jachens, R. C. (2003). Crustal structure of the Peninsular Ranges batholith from magnetic data: Implications for Gulf of California rifting. Geophysical Research Letters, 30(11).
* ↑ NASA. (n.d.). Earth Matters - What A Wonderful World: Pinacate Peaks. NASA. https://earthobservatory.nasa.gov/blogs/earthmatters/2017/11/10/what-a-wonderful-world-pinacate-peaks/.
* ↑ Wood, C. A. (1974). Reconnaissance geophysics and geology of the Pinacate craters, Sonora, Mexico. Bulletin Volcanologique, 38(1).
* ↑ The landforms of the EL pinacate and Gran Desierto DE Altar BIOSPHERE Reserve: Geo-mexico, the geography of Mexico. (2019, April 14). Retrieved April 13, 2021, from https://geo-mexico.com/?p=10003
* ↑ Average Weather in Puerto Peñasco. (n.d.). Retrieved April 06, 2021, from https://weatherspark.com/y/2368/Average-Weather-in-Puerto-Pe%C3%B1asco-Mexico-Year-Round
* ↑ The Sea of Cortez. (n.d.). https://www.rickbrusca.com/http___www.rickbrusca.com_index.html/Sea_of_Cortez.html.
* ↑ The Udall Center for studies in Public Policy. (2012, January). Moving Forward from Vulnerability to Adaptation: Climate Change, Drought, and water Demand in the Urbanizing Southwestern United States and Northern Mexico. http://udallcenter.arizona.edu/sarp/pdf/Ch3_PuertoPenasco.pdf.
* ↑ National wildlife REFUGES - welcome To yuma, Arizona - on the river's edge. (n.d.). Retrieved April 15, 2021, from https://www.visityuma.com/things-to-do/outdoors-and-nature/national-wildlife-refuges/?view=list&sort=qualityScore
* ↑ Yuma, Arizona desert plants. (n.d.). Retrieved April 15, 2021, from https://www.azmetro.com/yumaplants.html
* ↑ Camping in the Kofa National Wildlife REFUGE ARIZONA. (2020, June 06). Retrieved April 08, 2021, from https://www.loveyourrv.com/camping-in-the-kofa-national-wildlife-refuge-arizona/
* ↑ Kofa National Wildlife Refuge. (2020, April 30). Retrieved April 08, 2021, from https://www.arizonahighways.com/scenic-drives/kofa-national-wildlife-refuge
* ↑ Wildlife & habitat - KOFA - U.S. fish and Wildlife Service. (n.d.). Retrieved April 08, 2021, from https://www.fws.gov/refuge/Kofa/wildlife_and_habitat/index.html
* ↑ Jennie. (2016, February 08). Imperial National Wildlife Refuge IBA. Retrieved April 06, 2021, from http://aziba.org/?page_id=411www.fws.gov%2Frefuge%2Fimperial%2F
* ↑ Home - Imperial - U.S. Fish and Wildlife Service. U.S. Fish & Wildlife Service. (n.d.). https://www.fws.gov/refuge/Imperial/.
* ↑ Wildflowers. The Anza-Borrego Foundation. (2021, March 17). https://theabf.org/explore-anza-borrego/wildflowers/.
* ↑ Wildlife of the Anza-Borrego Desert. (n.d.). https://www.abdnha.org/wildlife-of-anza-borrego.htm.
* ↑ Posted by TB at 6:49 am, 15, M., Says:, M., 15, T., & Says:, T. (2018, April 17). Mexico's El pinacate and Gran Desierto DE Altar Biosphere reserve in SONORA GETS UNESCO World heritage STATUS: Geo-mexico, the geography of Mexico. Retrieved April 06, 2021, from https://geo-mexico.com/?p=9841
* ↑ Ecologists Claim Birds Disappearing From Quitobaquito Springs Due To Border Wall Construction. (n.d.). https://www.nationalparkstraveler.org/2020/09/ecologists-claim-birds-disappearing-quitobaquito-springs-due-border-wall-construction.
* ↑ Pearson, G., & Conner, C. (2000). The Quitobaquito Desert Pupfish, An Endangered Species within Organ Pipe Cactus National Monument: Historical Significance and Management Challenges. Natural Resources Journal, 40(2), 379–410.
* ↑ U.S. Department of the Interior. (n.d.). Organ Pipe Cactus International Biosphere Reserve. National Parks Service. https://www.nps.gov/orpi/learn/nature/biosphere.htm.
* ↑ J, F. (2019). Water is for fighting over: and other myths about water in the west. Island Press.
* ↑ Redondo, L., & Garcia, C. (2021). Interviews with residents of San Luis Rio Colorado, SON "El Rio" significance in their personal life.
* ↑ Background Information on the Salton Sea. CDFW Prod. (n.d.). https://wildlife.ca.gov/Regions/6/Salton-Sea-Program/Background.
* ↑ Salton Sea Description. (n.d.). http://www.sci.sdsu.edu/salton/Salton%20Sea%20Description.html.
* ↑ Salton Sea. Water Education Foundation. (n.d.). https://www.watereducation.org/aquapedia/salton-sea.
* ↑ Parker Dam Lake Havasu Reservoir. (n.d.). Retrieved April 06, 2021, from https://www.desertusa.com/colorado/parker_dam/du_parkerdam.html#:~:text=Parker%20Dam's%20primary%20purpose%20is,211%20billion%20gallons%20of%20water
* ↑ A. (2019, December 10). Lake Havasu City Water Conservation Plan. Retrieved April 10, 2021.
* ↑ News, M. S. C. (2020, February 26). Why Palo Verde, the country's largest nuclear plant, is cutting its wastewater use. Cronkite News - Arizona PBS. https://cronkitenews.azpbs.org/2020/02/25/palo-verde-nuclear-water-use/.
* ↑ The Ecological Impacts of a Border Wall. The Ecological Impacts of a Border Wall | Environmental Law Institute. (2017, April 4). http://www.eli.org/vibrant-environment-blog/ecological-impacts-border-wall.
* ↑ Ecologists Claim Birds Disappearing From Quitobaquito Springs Due To Border Wall Construction. (n.d.). https://www.nationalparkstraveler.org/2020/09/ecologists-claim-birds-disappearing-quitobaquito-springs-due-border-wall-construction.
* ↑ Guardian News and Media. (2019, December 29). Water-guzzling demands of Trump's border wall threaten fish species. The Guardian. https://www.theguardian.com/environment/2019/dec/29/trump-border-wall-water-fish-species-threatened.
* ↑ McCallum, J. W., Rowcliffe, J. M., & Cuthill, I. C. (n.d.). Conservation on International Boundaries: The Impact of Security Barriers on Selected Terrestrial Mammals in Four Protected Areas in Arizona, USA. PLOS ONE. https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0093679.
* ↑ Worland, J. (2017, January 26). Donald Trump Border Wall Proposal Would Harm the Environment. Time. https://time.com/4650178/donald-trump-border-wall-environment/.