Riparian Areas
1. Riparian area defined
The land along a river, lake, or marsh is called a riparian area. Riparian areas have unique plants and animals compared to the surrounding area. In a very dry area like a desert, the contrast between the riparian zone and the nearby desert is ___________________compared to a wetter environment, like a river running through a forest.
Although not a true riparian area, dry washes in the desert will sometimes have plant life distinct from the surrounding area, since water runs through the washes for a few hours after each rainstorm. For example, ironwood trees will often be found in Sonoran desert washes.
2. Arizona's Riparian areas
Arizona's riparian areas have been significantly altered in the past 100 years.
| Force that alters riparian areas | How would it alter the riparian area? |
| Dam | |
| Pumping water for homes and agriculture | |
| Irrigation canals for agriculture |
3. Water in Arizona
a. Surface water
1) Phoenix gets much surface water from the Salt and Verde Rivers watershed (all the streams and creeks flowing into the Salt and Verde Rivers).
2) The Colorado River flows from the mountains of Colorado through Arizona to the ocean at the Gulf of California (Rocky Point and the Sea of Cortez). This water is used for cities and farms. by the Central Arizona Project (CAP).
b. Aquifers
Aquifers are water stored underground. Tucson uses water from an aquifer under the city, although the rate of use has exceeded recharge rates, so the city now supplements with CAP water.
c. Map exercise
Look at the map of Arizona below and label all of the bolded cities, lakes, rivers and dams using the information provided. You will need to know these on the exam.
1) Cities: Phoenix (central Arizona), Tucson (southern Arizona), Flagstaff (northern Arizona), Rocky Point (Mexico), Yuma (southwest AZ) on the California border where the Gila and Colorado Rivers meet
2) Rivers, lakes and dams:
The Colorado River enters Arizona in the north from Utah out of Lake Powell and over the Glen Canyon Dam (1964). It continues west flowing through the Grand Canyon into Lake Mead in Nevada, and then over the Hoover Dam (1936). The Colorado river then heads south along the California/ Arizona border and flows into Lake Havusu. It flows over the Parker Dam (1939) and heads south. The small amount of water that is left eventually reaches the Gulf of California in Mexico.
Roosevelt Lake lies to the east of the city of Phoenix. It was created when the Roosevelt Dam (1912) was built. It empties into the Salt River which meets with the Verde River before it reaches Phoenix. Today, a series of dams lies along both the Salt and Verde Rivers and the water is diverted out of these lakes into canals for agriculture and urban use. Thus, the Salt River is dry as it runs through Phoenix. This contrasts with the situation when the Hohokum lived here and built an extensive series of canals directly from the Salt River used for irrigation. Many of these Hohokum canal paths have been followed by the SRP utility company in building its own canals. West of Phoenix, the Salt River flows into the Gila River which then flows into the Colorado and on to Mexico.
If you are having trouble finding the bolded terms, here is a link to a map of:
3) Arizona canals
b) Central Arizona Project (CAP) canal (Colorado River water from Lake Havasu to Phoenix and Tucson)
Note: These links are to maps in PDF format. You will need Adobe Reader which is a free download.
d. List reasons in favor and against building dams.
| In favor of dams | Against dams |
In 1999, the city of Gilbert opened an urban riparian area at the corner of Guadalupe and Greenfield roads. The ponds are filled with wastewater that has been treated, so that it is safe for irrigation. The water seeps down into an underground aquifer. Because the city of Gilbert lies in the Sonoran desert, the plant and animal life in the riparian area contrast sharply with the surrounding desert.
5. Plants
The contrast between desert plants and water plants is apparent. Aquatic plants often have large leaves since water is no longer a limiting factor. Internally, they have large internal air spaces to help provide oxygen to the roots and often for floatation. The root system functions only as an anchor and is smaller than in land plants.
6. Animals
a Birds
Water attracts both desert and water birds. Note the difference in adaptations between desert birds and water birds. Many of the water birds are temporary visitors, migrating to warmer regions, and do not stay here year round. At different times of the day and at different times of the year, there is a great variety in the types of birds that you will see.
Desert birds are often smaller, and get much of their water from their food. The cactus wren is the state bird of Arizona and an example of a desert adapted bird. They are most active in the early morning and at dusk, and seek shelter in the heat of day. By contrast, water birds such as the great blue heron are larger, suggesting they have access to abundant food supplies. Their long necks, beaks and legs are adapted for walking, swimming and feeding in an aquatic environments.
b. Plants
c. Other animals: Many desert animals are crepuscular, most active at dawn and dusk.
1) Insects
Flying insects are especially abundant by water sources. Many flying insects like dragonflies and mosquitoes lay their eggs in water. So in desert areas that lack water, flying insects are uncommon. Butterflies like the Painted lady and dragonflies like the blue dasher can sometimes be seen.
2) Cold-blooded invertebrates
Lizards like the long-nosed leopard lizard and toads such as the red spotted toad might be visible.