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Dams and freshwater ecosystemsGlobally, there are 45,000 or so large dams inoperation and collectively, they have had a majorimpact on freshwater ecosystems. Together withcanals and diversions, they have been blamed for thefragmentation of more than 60% of the world’slargest rivers. Dams have thus contributed to thehuge loss in freshwater biodiversity observed inrecent decades – according to WWF’s Living PlanetReport, more than half of 192 freshwater indicatorspecies are showing a population decline.

This is not to say that every single dam and reservoircauses unacceptable environmental problems. Someare relatively benign due to their design, locationand/or mitigation measures implemented. From anenvironmental perspective, of most concern arethose dams that have either a direct or indirectimpact on ecologically important areas, such asnationally protected areas or those of internationalimportance such as wetland sites designated underthe Ramsar convention. For example, Lake IchkeulNational Park, Tunisia’s only Ramsar site, has seenbird numbers collapse since three dams wereconstructed in its catchment in the 1980s and 90s.Once home to up to 20,000 wintering Greylag geese,their numbers are now reduced to less than 1000.

However, in many cases such severe impacts can, ifnot reversed, at least be reduced throughenvironmental mitigation measures. The WorldCommission on Dams’ (WCD) Strategic Priority 4(Sustaining Rivers and Livelihoods) has stressed theneed for viable compensation measures and therelease of environmental flows (WCD, 2000). This isnot only relevant for new dams but can also beapplied retrospectively to existing dams.

Mitigating the impactsThe environmental impacts of dams and mitigationmeasures to deal with them have been documentedextensively (e.g. Bizer, 2001). Three types ofmeasures are particularly important for the protectionof freshwater biodiversity – environmental flows,ecosystem restoration and fish loss mitigation.

Environmental flowsChanging the operational regime of dams to mimicnatural flows is one of the most importantenvironmental mitigation measures available.Maximising the output of a dam, whether forhydropower generation or water supply, can haveserious consequences both for ecosystems and otherusers as, inevitably, flow conditions downstream ofthe dam are altered. However, in many cases it ispossible to adjust the operational regime of a dam tobetter meet a variety of needs, both in the case ofexisting and new dams. So-called ‘environmentalflows’ provide critical contributions to river health,economic development and poverty alleviation

Environmental flows are not the same as ‘minimumflows’ which are now common in many dam projects.Nor are they natural flows but they aim to find abalance for meeting a variety of needs for watervolume, quality and timing, including those ofecosystems and downstream communities. World-wide, 230 rivers now have some kind of flowrestoration scheme in place. A well-known exampleis the Snowy River scheme in southeastern Australiawhere dams diverted 99% of stream flow from theriver’s headwaters. An agreement was signed in

Dams and freshwater ecosystems – repairing the damage

Lac Ichkeul National Park © WWF/U Collier

2000 by the Federal Government and theGovernments of Victoria and New South Waleswhich aims to restore the Snowy to 15% of its originalflow in 7 years, with an eventual target of 28%. Thewater for the environmental flows is being acquiredprimarily through investments in water savings.

Ecosystem restorationHabitat loss from dams can either be direct (i.e. thearea flooded) or indirect (loss of downstreamwetlands). Where no direct mitigation, for examplethrough environmental flows, is possible,compensatory measures should be considered. Thiscould involve purchasing suitable land and managingit for environmental protection purposes. Often,compensation involves areas next to or near theimpoundment that have been impacted by otherhuman activities (e.g. agriculture), with a focus onrestoration or rehabilitation, especially of nativevegetation. For example, in Brazil, the Peti hydroproject (originally commissioned in 1946) is nowsurrounded by a 606 ha nature reserve where thenative forest has been rehabilitated. CEMIG, theoperator, has also established on environmentalresearch centre and native species re-introductionprogramme. Another option for governments andother authorities is to designate other areas underthreat as ‘no go areas’ for dam developments.

Setting aside land for conservation can be difficultwhere land is required for agricultural production. Inthese instances, the promotion of sustainable landuse practices might be a better option. For example,the Salto Caxias scheme in Brazil promotes organicfarming as part of its mitigation package.

It also has to be recognised that habitat restorationdoes not entirely compensate for the loss of naturalareas, as it is very difficult (in particular in the case ofwetlands) to achieve similar biodiversity values.Nevertheless, the approach can be beneficial in thecase of existing dams where areas are already

degraded. Reforestation in particular can haveadditional benefits in terms of reducing erosion andhence reservoir sedimentation.

Fisheries impact mitigationDams can have a devastating impact on fisheries, forexample by blocking the passage of migratory fish totheir spawning grounds. Not all rivers have migratoryfish populations but where they exist, fish passes arenow often integrated into dam designs. In the case ofexisting dams, it is often possible to retrofit fishpasses. There are numerous designs and options forfacilitating fish passage but their effectiveness is verymuch design and species dependent.

Fish populations are also impacted due to habitatdestruction (for example of downstream wetlands)and alterations (in particular changes in streamflow,temperature and oxygen levels). Compensating forthis through the creation of artificial reservoir ortailwater fisheries (for example by introducing non-native fish species into reservoirs) is undesirablefrom a biodiversity point of view, although it can havesocial and economic benefits. It can also beexpensive, as it often requires frequent restockingthe reservoirs. Extreme care needs to be taken toavoid further impacts on native fish species by theintroduction of alien species.

The costs of mitigation – who pays?With new dams, it is now increasingly common tointegrate the cost of environmental mitigationmeasures into the project costs. For existing dams,the question of ‘who pays’ is a frequent theme,particularly in developing countries. In the case of theKafue Flats (see below), there are social andeconomic benefits in terms of fisheries and grazingwhich more than compensate for any losses inelectricity generation from a changed operationalregime. Such external benefits need to be recognisedby governments and operators.

One option is to integrate the cost of mitigationmeasures into electricity tariffs (or water usercharges in the case of non-hydro dams). In this case,the consumer/user pays. Otherwise, taxes or rentscan be imposed on the owner/developer to pay formitigation programmes. Other financing modelsinclude government/agency financing or financepackages from multilateral or bilateral agencies (forexample the World Bank or Global EnvironmentFund). However, the availability of this type of financeis limited.

The mitigation of existing dams can also be made acondition of the approval for new ones, withmitigation packages being integrated into the costs ofthe new project. Furthermore, in some countries,relicensing processes offer the opportunity tonegotiate mitigation programmes. For example, in theUnited Sates, the maximum duration of an operatinglicence is 50 years. Mitigation measures arenegotiated during relicensing and/or are determinedby government agencies responsible for wildlife

Peti hydro scheme nature reserve © WWF/U Collier

protection and are made part of the license. Thecompany seeking the license pays for thesemitigation measures, as well as the extensiveenvironmental studies that have to be carried out forthe relicensing process.

Mitigation and green hydro certificationAn independently certified approach tocomprehensive mitigation of environmental effectscan be found in the ‘naturemade’ green electricitylabel in Switzerland (www.naturemade.ch), whichis supported by WWF, other environmental andconsumer associations and a number of electricitycompanies. This renewable energy label providesfor the accreditation of new and existinghydropower plants under certain conditions andconsumers can chose to buy ‘green’ electricity ata premium price.

To achieve the highest standard, the ‘naturemadestar’ label, hydro plants have to meet strictenvironmental conditions. These includeenvironmental flows, sediment flushing, fishladders and protective measures for wetlandhabitats. Additionally, operators have to pay apercentage of their income into a fund forenvironmental improvement measures, includinghabitat restoration. The measures have to beadditional to those that need to be taken to meetthe certification criteria. The plant operator, localauthorities and environmental organisations jointlydecide the allocation of the fund. Fourteen Swisselectricity suppliers have gained certificationunder this label. Key to the credibility of this schemeis its independent statute with board membershipfrom industry, consumer and environmentalorganisations. In the United States, the Low ImpactHydropower Institute has a similar approach(www.lowimpacthydro.org).

Environmental flows for the Kafue FlatsEnvironmental flows are not solely a ‘luxury’ fordeveloped nations. South Africa’s National Water Act‘reserves’ an allocation of water to supportecosystem functions. In Zambia, WWF is working onestablishing an environmental flow regime in theKafue Flats, as part of a wider project on integratedwater resources management for the area. Theproject is a partnership with the Zambian ElectricitySupply Company (ZESCO) and the Ministry ofEnergy and Water Development (MEWD). Manyother stakeholders have been involved in projectdiscussions.

The Kafue River and Kafue Flats are part of theZambezi River Basin in Zambia. The Kafue Flatscover an area of about 6500 km2 and are recognisedas a major wetland resource both in ecological terms,with rare and endemic species, and in socio-economic terms because they support localindustries such as flood recession agriculture, dryseason cattle grazing and traditional fisheries. It isestimated that about 700,000 people live in, or in thevicinity of, the Kafue Flats.

The area’s natural water regime was radicallychanged after the construction of two dams in 1969and 1976. First, downstream from the wetlands, ahydropower plant was built in the Kafue Gorge. Thisinstallation supplies approximately 40% of Zambia’selectricity needs. Because of the nature of the KafueFlats a second dam was needed upstream to ensurea steady supply of river water and the Itezhi-tezhistorage dam was built 250 km upstream.

As a result of the construction of the two dams, astable river level throughout the year has replacedthe natural flood patterns in the Kafue Flats. Thechange in the water regime has meant that thepopulations of many species in the area have greatlydeclined. For example, the number of Kafue lechwe,a type of antelope endemic to the Kafue Flats, hasdecreased to a third of its original 1970 population of100,000. Elephants, rhinoceroses, giraffes and wilddogs have disappeared from the area entirely.Increased poaching in the wetlands has exacerbatedthe decline. Lower fishery yields and reducedavailability of grazing land as a result of the alteredflooding regime have also affected humancommunities.

To release an appropriate volume of water at theright time of year to restore the ecological health ofthe Kafue Flats floodplains, WWF is co-financingmodelling work analysing different flow regimes, aswell as the re-establishment of hydrologicalmonitoring stations. In May 2004, the ZambianPresident is expected to ‘turn on the taps’ and launchnew operational rules for the Itezhi-tezhi dam. Theproposed environmental flows are expected torestore and conserve the floodplains for the benefit ofnature and people’s livelihoods, while maintainingpower generation and the irrigation industry in thevalley.

Itezhi-tezhi dam spillway © WWF/U Collier

Dam relicensing - USAIn 1986, the United States Congress amended theFederal Power Act directing the Federal EnergyRegulatory Commission (which issues licences fordams) to give “equal consideration to the purposes ofenergy conservation, the protection, mitigation ofdamage to, and enhancement of, fish and wildlife(including related spawning grounds and habitat), theprotection of recreational opportunities, and thepreservation of other aspects of environmentalquality”. With the maximum life of a dam license setat 50 years, many dams are now undergoing theprocess of relicensing and have to achieve a betterbalance of these objectives. The 1920 FederalPower Act ensures citizen involvement in thisprocess, which can take many years.

For the past three years, WWF has participated inrelicensing efforts in the Klamath-Siskiyou region ofCalifornia and Oregon, an area well known for its wildsalmon. Built between 1908 and 1962, the sevenhydroelectric dams and one non-generating dam onthe Klamath River have a combined generatingcapacity of 151 megawatts. A new license for theKlamath Project is to be issued in 2006 and theoperator, Pacificorp, has carried out extensive newstudies of environmental impacts and mitigation,which are available to the public. WWF is working, incollaboration with partner NGO’s, to negotiate abetter conditions for aquatic and terrestrial species(including better stream flow, an increase indissolved oxygen and the provision of habitatcorridors) by serving on several working groups.

Conclusions and recommendationsExisting dams have major negative impacts onfreshwater habitats. But it is possible to mitigate atleast some of the environmental impacts. However,globally there is no consistent approach to achievingthis. In some countries, mitigation is now enshrined inlaw (for example, the European Union’s WaterFramework Directive requires the implementation ofcomprehensive mitigation measures to achieve goodecological status in ‘heavily modified water bodies’such as reservoirs) or is part of the relicensingprocess (as in the case of the US). Elsewhere,mitigation is a more ad hoc process. In the case ofthe Kafue flats, discussions and studies had beengoing on for a decade or more but it was the initiativeand funding from WWF that finally got the project offthe ground. In Switzerland, green consumerism is thedriving force between higher environmentalstandards at existing dams. While there are manymore positive examples like these, there are alsothousands of dams where there are no adequatemitigation measures.

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WWF thus calls on governments, operatorsand funding agencies to:

• Develop effective legislative frameworksor relicensing processes requiringenvironmental mitigation at existingdams;

• Link mitigation at existing dams to theapproval process for new dams;

• Provide more funding for mitigationpackages, especially in developingcountries;

• Develop mechanisms for sharing goodpractice and lessons learning onenvironmental mitigation.

urther readingizer, R. (2001) International Mechanisms forvoiding, mitigating and compensating the impacts of

arge dams on aquatic and related ecosystems andpecies.ttp://www.dams.org/docs/kbase/contrib/env249.pdf

yson, M., Bergkamp, G., Scanlon, J. (eds, 2003).low. The essentials of environmental flows. IUCN,land, Switzerland and Cambridge, UK

WF (2003) An Investor’s Guide to Dams, WWFams Initiative. http://www.panda.org/dams

orld Commission on Dams (2000) Dams andevelopment. Earthscan, London

© 2004Dam Right!WWF’s Dams InitiativePanda HouseWeyside Park, GodalmingSurrey, GU7 1XRUnited KingdomTel: +44 1483 426 [email protected]/dams

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