Resurrecting the Dammed: A Look at Colorado River Restoration

998 BioScience • December 2001 / Vol. 51 No. 12

Features

John Villalobos stands on the highground overlooking a backwater sloughof the Colorado River at the AhakhavTribal Preserve, a 1,000-acre park andwildlife refuge on land owned by the Col-orado River Indian Tribes in the SonoranDesert south of Parker, Arizona. Villalo-bos is surrounded by restored honey andscrewbean mesquites as well as cotton-woods and willows. The slough, a 2-mile-long side channel dredged by the Indiantribes and the US Bureau of Reclama-tion in 1998 and 1999, features exten-sive bulrushes and cattails and a half-dozen or so beaver lodges.

“This is the way it used to look allalong this valley,” says Villalobos, projectadministrator for the Ahakhav Preserve.

“We want to show people the way theriver used to be. This is a model for gov-ernment agencies trying to atone for theerrors that their dams have caused. Thisis a place that can support our nativespecies and where our people can comeand enjoy their own lands.We want to re-store at least part of that.”

Indeed, the Colorado River IndianTribes—a group of four southwesternNative American nations—have usedpart of their allotment of river water torestore 250 acres of aquatic habitat alongthe Colorado and another 250 acres of ri-parian areas since 1996. They plan to re-store 200 more acres over the next fewyears. Already, the numbers of vermil-ion flycatchers and Yuma clapper railshave increased here, and Bell’s vireos andsouthwestern willow flycatchers have

reappeared for the first time in years.“We are restoring our environmental her-itage,” says a proud Villalobos.

The Ahakhav Preserve is one of severalplaces on the Colorado River and its trib-utaries south of Lake Mead where gov-ernment agencies, Indian tribes, privategroups, and individual landowners areseeking to recreate at least a portion of theformer riparian ecosystem. Efforts areunder way or planned to restore the na-tive flora at selected sites and to bolster thepopulation of native Colorado River fishdecimated by a changed river and the in-troduction of new species. Further, acoalition of government agencies andprivate companies in three states is de-veloping a controversial multispecies con-servation plan for the river and its en-dangered wildlife.

Whether and to what extent such ef-forts work will depend on several fac-tors. Foremost among them is water, al-ways a rare commodity in the aridSouthwest. Can enough water be foundor diverted from current agricultural,municipal, and industrial users for envi-ronmental restoration? Which ap-proaches work best? Are changes neededin how and when the river flows? Is theUnited States responsible for endangeredspecies and habitat restoration along theColorado and its delta in Mexico?

The Colorado River flows 1,450 milesfrom the Rocky Mountains in Coloradosouthwest through the picturesquecanyons of Utah and Arizona before turn-

Resurrecting the Dammed: A Look at Colorado River

RestorationJ E F F R E Y P. C O H N

The Colorado River Indian Tribes have used part of their water allotment to restore habitat along the Colorado River, in the Ahakhav Tribal Preserve.

Photograph: Bureau of Reclamation.

Downloaded from https://academic.oup.com/bioscience/article-abstract/51/12/998/224044by gueston 23 February 2018

December 2001 / Vol. 51 No. 12 • BioScience 999

Features

ing south toward Mexico and the Gulf ofCalifornia. During its passage to the sea,the Colorado drops more than 10,000feet in elevation, at times generating dan-gerous whitewater rapids. The river andits tributaries drain 242,000 square milesin seven US states (8.5 percent of thecontinental United States) and another2,000 square miles in Mexico.

Before people started tinkering with it,the Colorado often flooded in spring andearly summer, when rain and runoff frommelting snow turned the river into a rag-ing giant. The floods swept away salts,plants, and ground litter. In the process,they scoured old sandbars and beachesand laid down new ones; created back-water marshes, oxbows, and sloughs; andraised groundwater levels. As summerturned into fall and winter, the river grad-ually shrank, in some years to a meretrickle. How much water flowed varied,often widely, from season to season andyear to year.

Those days are gone. The Colorado isnow one of the most controlled rivers inthe world.Virtually every drop of its wa-ter is managed, accounted for, and allo-cated to some user. In the United States,the Colorado is divided into upper andlower basins, each entitled to 7.5 millionacre-feet of water a year. (One acre-footis the amount of water needed to coverone acre of ground to a depth of 1 foot,or nearly 326,000 gallons.) Under a 1944treaty, the United States delivers 1.5 mil-lion acre-feet to Mexico where the rivercrosses the border near Yuma, Arizona.The 16.5 million acre-feet total exceedsthe river’s average annual flow of about15 million acre-feet. Fortunately, the up-per basin states do not use all the waterallotted to them, and the last two decadeshave seen mostly above-average flows.

Starting with the Laguna Dam northof Yuma, which was completed in 1909,the Colorado’s flow is now interrupted by10 major dams, 4 reservoirs, and morethan 80 diversions. The former includesthe Hoover and Glen Canyon Dams,which together hold more than 55 millionacre-feet of water. Altogether, water fromthe Colorado irrigates more than 3.7 mil-lion acres in the United States and Mex-ico and provides drinking water to nearly30 million people in cities from Las

Vegas and Phoenix to Los Angeles, Mex-icali, and Tijuana. The dams also gener-ate more than 4,400 megawatts of elec-tricity, all in the United States.

By preventing the Colorado fromflooding, the dams and reservoirs have al-tered the river. With its more uniform,year-round flow, no floods now sweepdown the river. No longer are salts orplant debris washed away, nor are anynew backwaters created or old onesrecharged. The dams have also changedthe Colorado from a warm- to a cold-water river, held back sediment thatwould otherwise create new sandbars,and kept nearly all freshwater from reach-ing the delta in Mexico. In 1981, writerPhilip Fradkin declared the Colorado “ariver no more” (A River No More: TheColorado River and the West [New York:Knopf]).

As a result, the cottonwoods, willows,and mesquites that once lined large sec-tions of the Colorado and its tributariesare now largely gone. Although no oneknows for sure, perhaps as much as400,000 acres of riparian habitat existedbefore dams were built, says RobertOhmart, an Arizona State University bi-ologist. By 1938, three years after theHoover Dam was completed, nearly90,000 acres of riparian habitat remained,according to a 1998 Bureau of Reclama-tion report. Today, the bureau estimatesthat only about 6,000 acres still exist.Some older cottonwoods and willowscan still be found, but few young treesnow grow. Most riparian areas are nowdominated by saltcedar, a Eurasian tree

introduced in the 19th century as an or-namental and to control erosion. Alsocalled tamarisk, saltcedar has become awidespread pest in the West. It can tol-erate and even thrive in the high-salt,dry soils that kill cottonwoods and wil-lows or inhibit their seeds from grow-ing.

As cottonwoods and willows declined,so too have southwestern willow fly-catchers.A subspecies of Traill’s flycatcher,the southwestern willow flycatcher wasonce locally common along the riversand streams of the arid southwesternUnited States and northern Mexico. Noone knows the bird’s former numbers,but an estimated 900 territories werefound in recent surveys, says Robert Mar-shall, a former US Fish and Wildlife Ser-vice biologist now with The Nature Con-servancy’s Arizona chapter in Tucson.

Acting on a petition from the Centerfor Biological Diversity, a Tucson-basedenvironmental group, FWS listed thesouthwestern willow flycatcher as en-dangered in 1995. It was the first riparianbird in the southwestern United States tobe listed. Next, the agency issued a bio-logical opinion in 1997 requiring the Bu-reau of Reclamation to consider how itsroutine dam operations affected the fly-catcher and other endangered species inthe United States. Earlier, in 1994, FWShad designated critical habitat for four na-tive Colorado River fish. Together, saysMarshall, those actions “forced all federaland state agencies to pay attention to is-sues and species that previously had beengiven little more than lip service. Theygave environmentalists leverage to com-pel action.”

Saving the southwestern willow fly-catcher and other endangered speciesmeans recreating the riparian habitatsthat once flourished along the ColoradoRiver and its tributaries. Early restorationefforts languished, according to BertinAnderson, president of the Revegetationand Wildlife Management Center inBlythe, California. Most were too smalland few adequately tested the soil, watertable depth, or salinity levels. “You haveto reclaim the land,” says Anderson. Inparticular, he advises, the land has to beflushed with water periodically to leachout salts and simulate natural flooding.

Listed as endangered since 1995, thesouthwestern willow flycatcher once

thrived in riparian habitat throughoutthe arid Southwest. Photograph:

Bureau of Reclamation.


Beyond the Colorado River IndianTribes’ Ahakhav Preserve, perhaps themost extensive restorations today are onthe four national wildlife refuges thatprotect much of the Colorado south ofLake Mead: Havasu, Bill Williams River,Cibola, and Imperial. These and otherefforts are creating small but potentiallyimportant patches of riparian habitats.

Created in 1941, Imperial NationalWildlife Refuge features 25,125 acres ofSonoran Desert, riparian habitats, andthe last nonchannelized stretch of thelower Colorado River in the United States.Refuge biologists established a 3.5-acrecottonwood and willow nursery in 1993.Beginning at one year of age, the trees arecut off at the bottom, stripped of theirleaves, cut into poles, and planted in for-mer backwater or other wet areas at Im-perial. One such spot is an open field atImperial where saltcedar and other exoticplants have been removed. Here, the polesare growing into full-fledged cotton-woods. Dikes and dirt berms keep waterpiped from the river from escaping. Morethan 50 acres at and off the refuge are nowwet enough to support cottonwoods andother native riparian plants. Further re-planting efforts will use nursery-grownseedlings, says Renee Robichaud, an FWSbiologist at Imperial.

Farther north, Cibola National WildlifeRefuge protects more than 17,000 acres.Created in 1964 as mitigation for ripar-ian habitats destroyed along the Col-orado, Cibola includes a new river chan-

nel dug to compensate for the old, nowstraightened one. Because the new chan-nel is wider and has more water than theold one, says Brenda Zaun, a wildlife bi-ologist at Cibola, thousands of ducks,Canada geese, and sandhill cranes winterat the refuge, the largest flocks in Ari-zona. Refuge biologists have also begunplanting cottonwoods and willows alongthe edges of a 150-acre site being clearedto create a sandhill crane roosting area, aswell as on a smaller 120-acre site.

Still farther north along the Colorado,Kathleen Blair and her colleagues at theBill Williams River National WildlifeRefuge had to do no work to restore nat-ural riparian habitats along a section ofthe river’s tributary. Heavy rain sentfloodwaters cascading down the BillWilliams in 1993 and 1995, washing awayyears of accumulated salt, plants, and de-bris from former agricultural fields, saysBlair, the refuge’s wildlife biologist. Thefloods naturally restored a 2,200-acresection of the refuge. Cottonwoods, wil-lows, and mesquites have recolonized thesecondary flood plains, while palo verdetrees occupy the more distant hillsides.“Within a few weeks of the floods we


Features

Restoration efforts began in 1993 at Imperial National Wildlife Refuge. Now, morethan 50 acres get enough water to support cottonwoods and other native riparian

plants. Photograph: Bureau of Reclamation.

The Nature Trail at Cibola National Wildlife Refuge is a 2-year-old revegetationsite. Thousands of ducks, Canada geese, and sandhill cranes winter at the refuge, the

largest flocks in Arizona. Photograph: Brenda Zaun.



Features

had seedlings growing just about every-where they could grow,”Blair recalls of thefloods’ aftermath. “Those trees knowwhere to grow better than we do.We’ll letnature and the river determine the courserather than try to impose our humancourse.”

The northernmost of the four refuges,Havasu National Wildlife Refuge en-compasses 33,500 acres of wetlands andMojave Desert habitats along LakeHavasu, a reservoir created by the ParkerDam on the Colorado. Refuge biologistshave begun restoring 1,500 acres in andaround Topock Marsh, a river backwater.The marsh had become clogged with cat-tails and woody plants, a sign that it wasfilling in, says Matthew Connolly, an FWSwildlife biologist formerly at Havasu,now at the Ohio River Islands NationalWildlife Refuge in West Virginia. Previ-ously, Colorado River floods would sweepout the cattails, prevent woody plantsfrom intruding, and keep the marsh wet.Because the floods come no more and therefuge has no way to simulate them, Con-nolly’s colleagues plan to burn the cattailsto enhance habitat for the endangeredYuma clapper rail.

Havasu biologists are also restoringthe refuge’s 220-acre Lake Beal, yet an-other Colorado River backwater. FWSand the Bureau of Reclamation biolo-gists began dredging more than 150,000

cubic yards of sediment from the lake inMay to create a refuge for native Col-orado River fishes, which have been es-pecially hard hit by changes in the river.They were adapted to a flood and thenlow-flow regime, warm waters, and anuninterrupted river. Moreover, intro-duced trout, sunfish, bass, carp, and cat-fish eat the native species’ eggs and young,says Charles Minckley, an FWS fisheriesbiologist.Virtually no young native Col-

orado fishes survive into adulthood now.All are listed as endangered or threat-ened and some have disappeared fromlarge sections of the river.

Wildlife biologists are particularly con-cerned for bonytail chubs and razorbacksuckers.“They are essentially gone,” saysMinckley, who adds that no bonytailshave been known to reproduce success-fully in the wild for 30 or 40 years. Some1,500 hatchery-raised bonytails have beenreleased since 1996 into Lake Mojave,the Colorado north of the Davis Dam,

Havasu National Wildlife Refuge encompasses 33,500 acres of wetlands and Mojave Desert habitats. Photograph: Bureau of Reclamation.

Lake Havasu is a reservoir created by the Parker Dam on the Colorado.Photograph: Bureau of Reclamation.

Topock Marsh, no longer swept byperiodic floods, was clogged with

cattails and woody plants until refugebiologists began restoring the marsh.Photograph: Bureau of Reclamation.


but few are known to have survived. Anestimated 8,000 razorbacks still live inLake Mojave, most resulting from re-leases of hatchery-raised fish, but this isdown from 65,000 two decades ago.

Additionally, FWS biologists are rais-ing razorbacks in ponds at the BillWilliams refuge. Fifty have been releasedinto the river since 1998, and biologistsplan to release bonytails as well later thisyear. The fish are released behind beaverdams, where they are protected from thelarger introduced fish downstream. Withany luck, Minckley says, they will grow big

enough to avoid being eaten when thenext big flood occurs and washes thempast the beaver dams.

Meanwhile, five federal agencies joinedwith six state water, natural resource, andwildlife agencies, three Indian tribes, andthe local water districts and power com-panies in California,Arizona, and Nevadato launch a $6.7 million multispeciesconservation planning effort for the Col-orado in 1994. Multispecies or habitatconservation plans allow state and localgovernments as well as private companiesand landowners to protect endangeredspecies and their ecosystems in returnfor incidental take permits under the En-dangered Species Act.“We wanted to takea proactive approach,” says MartinMeisler, a senior environmental special-ist for the Metropolitan Water District ofSouthern California, which supplies wa-ter to Los Angeles. The groups expect tosubmit a draft conservation plan to FWSby February 2002 and a final plan by theend of that year, according to Meisler.

In all, the plan will cover 57 mam-mals, birds, and fish that are listed or arebeing considered for listing by FWS andCalifornia as endangered or threatened.“We want to work toward the recovery ofendangered and threatened species and tohelp prevent the need to list others inthe future,” Meisler says. The plannersare looking for what they call “conserva-tion opportunity areas” along the Col-orado and its tributaries. So far, they haveidentified more than 60 sites, from LakeMead south to Yuma, where riparianhabitats can be restored, old sloughs andoxbows recreated, and new ponds dugto compensate for lost wetlands.

The plan envisions paying farmers,Indian tribes, and other landowners togrow cottonwoods, willows, and othernative plants rather than commercialcrops.“Some of the best riparian habitatsare on agricultural lands,” says SamSpiller, an FWS wildlife biologist who isthe agency’s lower Colorado River coor-dinator. Those lands already have irriga-tion ditches, berms and dikes, and, mostimportant, the right to water. “We needto develop agreements with willinglandowners to reestablish major tractsof riparian habitats,” Spiller says.“With-out water, most hoped-for restorationjust won’t happen.”

Spiller points to two places in south-western Arizona that serve as pilot pro-jects for the conservation opportunityconcept. One is a 40-acre site on the GilaRiver east of Yuma near Tacna. The otheris Pratt Farms, a 12-acre tract on the Col-orado north of the Laguna Dam. Both areformer farms, neither of which is nowgrowing crops, on land owned by theBureau of Land Management. The Bu-reau of Reclamation funded the plantingof honey mesquite and palo verde treeson the Tacna site in the mid 1980s and therestoration of cottonwoods and willowsat Pratt Farms in 1999. “Oh, definitely,there are still trees there,”says Glen Gould,a BOR natural resource specialist. “Cot-tonwoods and willows are a struggle, butthe mesquites and palo verdes are doingfine on their own.”

Not all observers are so upbeat. “It’s astep in the right direction, but you can’trestore riparian habitats with postagestamp–sized patches,” says Arizona StateUniversity’s Ohmart. At least 60 acres areneeded to recreate fully functioning ri-parian habitats and attract southwesternwillow flycatchers and other birds. “It’sterrible to use irrigation water to growcottonwoods and willows,”he adds.“Toomuch salt and litter will accumulate.Youneed a big flood every 25 or 50 years torearrange stuff. A naturally flowing riverwill do that.”

Julie Stromberg agrees. Stromberg, anassociate professor of plant biology atArizona State University, contends thatcurrent restoration efforts focus too muchon cottonwoods, willows, and mesquites,rather than the full array of 300–500


Features

An estimated 65,000 razorback suckersswam in Lake Mohave two decadesago. Today, there are approximately

8,000 razorbacks, most resulting fromreleases of hatchery-raised fish.

Photograph: Bureau of Reclamation

Bonytail chubs are no longer reproducing in the wild. Efforts to restock Lake Mojavewith hatchery-raised bonytails have been largely unsuccessful.

Photograph: Bureau of Reclamation.


riparian plants naturally found alongSonoran Desert streams. Her researchalong the Hassayampa and Agua FriaRivers, both tributaries of the Gila west ofPhoenix, shows that even soils that havebeen dry for 30 or 40 years still containseeds of riparian plants that will fare bet-ter than transplanted, nursery-growntrees once water is added. Her prescrip-tion: Dig up and move the soil to restorecomplete riparian habitats, while alsorestoring the Colorado’s natural flowsand floods, which allow seeds to germi-nate on their own.

“It’s a band-aid approach that’s okayfor the short term,” Stromberg says ofthe conservation opportunity approach.“It is not the be-all or end-all of restor-ing natural ecosystems. What happenswhen there is a drought? How much ofthe river are we willing to devote to restor-ing native species?” In fact, no currentusers of Colorado water have yet agreedto give up their water rights for environ-mental restoration anywhere along theriver. “We would prefer to do conserva-tion on land that already has water,” saysthe MWD’s Meisler, who notes that alloptions for securing water for conserva-tion areas have to be assessed first.

One need that is not being assessedby the multispecies conservation plan isthat of the Colorado’s delta in Mexico.Once covering almost 2 million acres, anarea the size of Rhode Island, the deltashrank and dried out as dams in theUnited States held back water. Since theearly 1980s, though, the delta has undergone a remarkable if far-from-complete comeback. El Niño floods inthe 1980s and 1990s added more water tothe river than the reservoirs could hold orthan users in the United States and Mex-ico needed.As a result, the delta’s wetlandsnow cover 150,000 acres.

Whether that comeback can be main-tained or extended remains unclear, how-ever. Edward Glenn, a professor of soil,water, and environmental sciences at theUniversity of Arizona in Tucson, calcu-lates that an average annual flow of 50,000acre-feet in the Colorado River from the

Morelos Dam below Yuma in Mexico,and a flood of 260,000 acre-feet every 4or 5 years, would be sufficient to at leastmaintain the current delta.

A coalition of mostly regional and lo-cal conservation groups is waging a pub-lic campaign urging the Bureau of Recla-mation to dedicate 1 percent of theColorado’s annual flow, or about 150,000acre-feet, to environmental restorationin the delta.“It’s a reasonable request,”ar-gues Lisa Force, program director forLiving Rivers, a Phoenix-based groupthat is leading the effort.“So much wateris wasted by inefficient irrigation meth-ods. Sprinkler or drip irrigation methods[alone] would save 43,000 acre-feet ofwater.”

In the meantime, a report issued by theSonoran Institute, a Tucson-based envi-ronmental group, has urged two imme-diate steps to increase water for the delta.One involves buying marginal farmlandwith water rights in Mexico and usingthat water to restore natural habitatsalong the Colorado south of the MorelosDam. The second would be to divert75,000 acre-feet of brackish, agriculturalrunoff from around Yuma to targetedecological areas in Mexico.

For their part, Bureau of Reclamationofficials say they cannot use water forenvironmental restoration, at least notnow. “This is very complex,” explainsThomas Shrader, a BOR ecologist, cit-ing US Army Corps of Engineers’ rulesabout flood control on the Colorado.Moreover, Shrader adds, “It is not ourwater.” Indeed, the water belongs to theseven basin states under a 1922 rivercompact and subsequent federal laws andUS Supreme Court rulings, and to Mex-ico under the 1944 treaty. “We cannotrelease water outside those entitlementsunless requested by a state or [unless partof] a scheduled release to Mexico,”Shrader says.“Any request for [water for]environmental restoration would haveto come from a state.”To date, none of theColorado River states has volunteered togive up some of their allotted water.

The Center for Biological Diversityand several other US and Mexican envi-ronmental groups are seeking to changethat. They sued the Bureau of Reclama-tion, US Fish and Wildlife Service, andNational Marine Fisheries Service underthe Endangered Species Act in 2000. Thesuit charges the agencies have failed toconsider the effects of US dams on fishand other US-listed endangered speciesin the Gulf of California and the Col-orado River delta in Mexico.

“We want the federal government toadmit that it is responsible for its actionson species even if they are beyond USborders,” says David Hogan, the Centerfor Biological Diversity’s river programsmanager. “We want to get water legallydedicated for conservation.” The centerand Defenders of Wildlife also pulledtheir representatives from the conserva-tion planning effort last year when themultispecies conservation plan’s steer-ing committee refused to extend the plan’spurview to the delta. Three other US en-vironmental groups had left earlier forunrelated reasons.

No decision on the lawsuit has yetbeen announced. However it is decided,major changes are needed to truly re-store riparian habitats along the Col-orado, states Mark Briggs, the SonoranInstitute’s science director.“If we can al-ter the river’s management even a little bitto get a guaranteed amount of good qual-ity water at the right times, we can main-tain and reestablish native species,”Briggssays. “The power of nature is so muchstronger than planting. Significantrestoration simply will not happen unlesswe address how we manage the Colorado.” ❑

Jeffrey P. Cohn, a Takoma,Maryland–based freelance sciencewriter, is a frequent contributor to

BioScience.


Features


Documents

Resurrecting the Dammed: A Look at Colorado River Restoration