Water – riparian and wildlife 2.3

What is a fluvial ecosystem?

Ecological systems dominated by running water (streams and rivers); also called lotic systems.

What is a river channel?

The physical pathway or depression in which river water flows.

What is a floodplain?

Flat land adjacent to a river that periodically floods; supports nutrient-rich soils and riparian vegetation.

What is a lentic ecosystem?

Still-water systems such as lakes and ponds with little to no flow.

What defines a riparian area?

The interface between land and water (e.g., rivers, lakes, wetlands); supports unique, lush vegetation and critical wildlife habitat.

What does a hydrograph show?

A graph displaying river discharge (flow) over time; altered by dams.

What is an ecological engineer?

A species that manipulates habitat or ecosystem processes through its activities (e.g., beavers building dams).

What is a keystone species?

A species with a disproportionately large effect on its ecosystem relative to its abundance (e.g., beavers create habitat for many species).

How is the Colorado River drainage divided for management?

Into the Upper Basin (CO, UT, northern AZ) and Lower Basin (AZ, NV, NM, CA, Mexico), managed separately for water use.

What are five main effects of dams on river ecosystems?

1.Alter seasonal water discharge patterns

2. Reduce annual water discharge

3. Moderate water temperature

4. Reduce silt/nutrient load

5. Reduce native fish, increase non-natives

Give an example of pre- and post-dam discharge change.

Pre-dams: spring floods from snowmelt; Post-dams: steady, low flow with no flood peaks.

How has the Colorado River delta changed in 100 years?

Once lush and biologically rich ("Green Lagoons"), now largely dry and disconnected from the sea due to reduced discharge; restoration projects underway.

Why is spring flooding important to native fish?

Triggers spawning cycles and creates floodplain habitats vital for reproduction and seed germination (e.g., cottonwood trees).

How do dams affect native fish populations?

Native species evolved in warm, silty, flood-prone systems; dams create cold, clear, stable flows favoring non-native species.

Provide examples of non-native fish that replaced natives.

Bass, pike, walleye, and rainbow trout outcompete native warm-water fish (e.g., bluehead sucker) in altered Colorado River systems.

What are the ecological impacts of non-native fish?

Competition, predation, disease, and hybridization with native fish; ecosystem transformation.

How widespread are dams in the U.S.?

Over 75,000 dams >2 m high, plus 2.5 million smaller water-control structures; only 42 free-flowing rivers >200 km remain.

How can dam effects be mitigated?

-Fish ladders for migration

-Controlled "high-flow" releases to mimic natural floods

-Restoration of sandbars and riparian habitats

Why are dams removed?

To restore natural river processes and remove toxic sediment buildup (e.g., Blackfoot & Clarks Fork Rivers, MT).

How are beavers ecological engineers?

Build natural dams that store water, expand flood basins, and create wetlands that benefit diverse species.

Why are beavers keystone species?

Their dam-building creates vital habitat; their removal disrupts many species dependent on wetlands.

Where does Arizona's water come from?

36% Colorado River, 21% in-state rivers, 3% reclaimed water, 40% groundwater.

How is Arizona's water used?

74% agriculture, 21% municipal, 5% industrial.

Where does Phoenix get its water?

Mainly from the Colorado River (via CAP) and Salt River (via Roosevelt Lake).

What is the CAP canal and why was it built?

A 336-mile aqueduct system transporting Colorado River water from Lake Havasu to Phoenix and Tucson for human and agricultural use.

What are key structural features of CAP canals?

Cement-lined, steep-walled, fenced, and largely vegetation-free—barriers to wildlife movement and survival.

How do canals affect wildlife?

-Create barriers to animal movement

-Cause drownings of trapped animals

-Fragment habitats

How can CAP canal impacts be mitigated?

By installing underpasses, culverts, and overpasses to allow safe wildlife crossings.

What was the goal of the Salt River Wildlife Project at ASU?

To study wildlife responses to water, vegetation, and urbanization along the Salt River using 43 wildlife cameras.

What were key findings?

41 species detected; wildlife distributions varied by urbanization level.

Species Found Mainly in Wildlands

Feral horses, javelina, bobcats, mule deer, badger, mountain lion.

Species Found Across All Areas

Coyote, raccoon, cottontail rabbit, humans (recreationists).

Species Found in Urban Areas

Free-roaming dogs and cats.

What conservation measures were discussed?

Restore riparian vegetation and wetlands (e.g., Rio Salado, Rio Reimagined) to improve year-round wildlife habitat.

What is the main takeaway of riparian ecology in wildlife management?

Maintaining and restoring healthy river corridors and riparian areas is essential for biodiversity, ecosystem health, and sustainable water use in Arizona and beyond.