Mark WILLIAMS, Ira ARTZ, Krey PRICE

Restoring Ecosystem Habitat in the Arid Southwestern United States:

Lessons Learned

Tetra Tech, Inc. United States

Ecosystem Restoration in the

United States

Since 1986, the agency most responsible for providing large-scale, ecosystem restoration projects in the US has been the US Army Corps of Engineers

Civil works projects for restoration often $100’s of millions of dollars, with the Everglades costing into the $billions.

Tetra Tech has been fortunate to provide support for many restoration projects, especially in the arid Southwestern U.S.

Problems in the Arid Southwest

NRCS

Dryland Rivers

Hyper-arid environment

Southwestern U.S.

annual precipitation

< 20 - 50 cm

Evapotranspiration

> 100 cm

Even though riparian areas represent <1% of the region’s area, they support > 50% of the nesting bird species and

>75% of vertebrate wildlife species(Johnson et al., 1977,

and Gillis, 1991).

Problems in the Arid Southwest

Ecosystems like this used to be much more common

Prior to dam construction and groundwater overdraft, many streams were perennial

The meandering channels included sandbars and backwaters.

Problems in the Arid Southwest

Cottonwoods, willows, mesquite forests, and cienegas used to fill the floodplain.

Problems in the Arid Southwest

Degradation caused by upstream dams, drought, climate change, and urban impacts such as groundwater overdraft, floodplain encroachment, habitat loss, modified hydrology, landfills, mining, invasive species, bank stabilization and channelisation

Problems in the Arid Southwest

USGS

Arizona stream: 1904 and recent

Lack of vegetation leads to unstable banks, as shown here in 1978 flood event on the Rillito River

Problems in the Arid Southwest

USGS

70 m of lateral channel migration

Problems in the Arid Southwest

USGS1850

2000

1940

The southwest has become increasingly urbanised

Restoration of riparian ecosystems in the Sonoran Desert considered critical by the Nature Conservancy

The Corps of Engineers and local municipalities have cost-shared several ecosystem restoration studies in the Phoenix and Tucson areas, in Arizona

Opportunities for Restoration

USGS

New

M

exic

o

ARIZONA

Utah

Phoenix

Tucson

Flagstaff

Salt River Watershed

Verde River

Watershed

Gila River

Watershed

Opportunities for Restoration

Tetra Tech’s role has been to provide planning, economic and environmental analysis, and design support to 3 major projects in the 34,000 square kilometer Salt River watershed, in the Phoenix metropolitan area, ArizonaTres Rios

Rio Salado Va Shly’ay Akimel

New

M

exic

o

Opportunities for Restoration

Project benefits include the following categories:

Habitat creation and restoration

Removal of invasives

Restoration of gravel pits

Restabilisation of the geomorphic regime

Water supply through infiltration

Flood risk management

Recreation

New

M

exic

o

Restoration Objectives

Restoration of a more natural riverine environment:

Return ecosystem functions

Return species diversity

Replace lost riparian habitat

Scrub-ShrubMesquite Mesquite

Bosque Wetland Ponded

Flow

WetlandCottonwood

Willow

Cottonwood

Willow

New

M

exic

o

Lesson Learned

The challenge in developing a restoration plan is finding the most cost efficient–yet effective–solution Federal water resource guidelines are strict

on economic benefit/cost analyses Relies on comparing a multitude of

possible measures Combined into alternatives

Reach Structure & Content Cleanup Temp. Housing Total

2L 42$ 10$ 0.4$ 52$

3L 2$ 1$ 0.1$ 3$

4L 2$ -$ 0.1$ 2$

5L 27$ 4$ 0.9$ 32$

6L 11$ 3$ 0.1$ 14$

Total - S. of River 84$ 18$ 1.6$ 104$

5R 123$ 5$ -$ 128$

6R 4$ 0.5$ -$ 5$

Total - N. of River 127$ 6$ -$ 133$

Total 211$ 24$ 2$ 236$

Notes: Damages for Reaches Not Shown are Minimal

Rio Salado Oeste

Without Project Equivalent Annual Damages

(in $1,000s)

Rio Salado Oeste Incremental Analysis

Alt 5A

Alt 5B

Alt 5

Alt 4

Alt 2

$0

$2,000

$4,000

$6,000

$8,000

$10,000

$12,000

$14,000

$16,000

51 165 240 253 267

AAFCU's

Avg

An

nu

al C

osts

($1,0

00)

New

M

exic

o

Cost Effectiveness Analysis

Use of IWR-Plan Incremental analysis program Analyzes thousands of possible combinations

of potential features Cost inputs compared to habitat units outputs Results in “best-buy” and “optimised” plans Used nationwide

0 100 3000

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

20,000

Mon

eta

ry C

osts

33 51 87 165 184 187 240 253 267

4

Refine

2

55B

2

3

1

5A

NOT Cost Effective

“ Best Buy “

Cost Effectiveness Analysis

Benefits:

Habitat Units

New

M

exic

o

Tres Rios Project

Located where three rivers meet (“Tres Rios”): the Salt, the Gila, and the Agua Fria

The project began as a means of treating treatment plant effluent using constructed wetlands

The Plan Formulation analysis justified a 10-km, $110 million restoration project

Tres Rios

• $110 M

• 11 river kilometers

• Restoration (600 ha)

• Levee (100-year)

• Recreation/education

• Cultural mitigation

IN CONSTRUCTION.

SPONSORS:

City of Phoenix/Gila River Indian Community

91

stA

ven

ue

Open Water

MarshesRiparian

Corridors

Flow Regulating

Wetlands

(see next slide)

N

Tres Rios ProjectPlan Overview Overbank Wetlands

Flood Control

Levee

Flow Regulating / Constructed

Wetlands

New

M

exic

o

Flow Regulating / Constructed

Wetlands Wetlands even out diurnal treatment plant peaks for more uniform treatment in constructed wetlands

Outflow then piped along top of bank with flow outlets into the overbank wetlands

Overbank Wetlands (OBW)

Salt River

USACE

Stormwater

Channel

Effluent Channel

FRW Inlet

Structure

Force

Mai

ns

FRW 1

FRW 2

FRW 3

DW A

DW B

Discharge

Structure

FRW 1

Emergent Zone/Hummocks

Open (Deep) Water

Road/Maintenance Access

Island

Riparian Corridors

Open Water Marsh

Overbank Wetlands

SALT RIVER

AUXILLARY

DISCHARGE

USACE

PIPE INLET

OVB - NORTH OBW

CULVERTS

SALT

RIVER

OVB - SOUTH

DISCHARGE

SPILLWAY

OVB-SOUTH

DISCHARGE

SPILLWAY

OVB-NORTH

USACE - L

EVEE

EFFLUENT

CHANNEL

Dimensions

Total Length = 2743 m

Total Area = 52 ha

Aquatic = 4.5 ha Wetland = 32.6 ha

Riparian = 6.8 ha Mesquite = 2.3 ha

Floodplain Terrace = 5.8 ha

New Levee Alignment

Va Shly’ay Akimel

Historic Condition: Perennial water

High water table

Braided & meandering

Cottonwood/willow,mesquite communities

Braided and meandering

Va Shly’ay Akimel

Current condition: Incised, isolated low-flow channels

Erosion during higher flows

Gravel pits have drained groundwater and degraded habitat

Authorized Project

Habitat enhancement Terracing / channel re-shaping Grade control structures Bank stabilization Open water / wetlands Cultural and ecological education centers Recreation

Authorized Project

Authorized Project Restores:

360 hectares cottonwood/willow

150 hectares mesquite

80 hectares wetlands

10 hectares Sonoran desert scrub shrub

approximately 8 km of maintained trails

$140 M 22 river km

Rio Salado Project

First ecosystem restoration project for which the Army Corps of Engineers received authorization

Challenges included scrutiny by higher authority on high cost of habitat units relative to projects in more hydric communities in the eastern United States

Use of potentially-contaminated groundwater for initial irrigation also resulted in scrutiny

Rio Salado ProjectAdditional constraints:

Regulated Hydrology – upstream dams dampen the natural peak flow conditions

Poor groundwater quality Need to maintain flood conveyance capacity Source and cost of water Birdstrikes to aircraft a threat Ongoing gravel mining operations

Lessons Learned (continued)

The challenge in restoration projects is to find creative and defensible solutions

Authorization granted by higher Corps’ authorityGroundwater treatment allowed – determined to be

least cost source of supply

Wetland locations for bird refuges moved

Agreements reached with mining operators

Restoration Success

Cost = $100M Length = 10 kilometers 275 hectares restored

Demonstration project shown

Rio Salado Project

2003 2005 2007

Gila River Indian CommunitySalt River Pima-

Maricopa Indian Community

Flood Control District of Maricopa County

US ArmyCorps of Engineers

Primary Lesson Learned

Partnerships are Critical for Success

Questions?

Tetra Tech would like to acknowledge

and thank the US Army Corps of

Engineers, Phoenix office, for making

past graphics available