Panel 4:
Large Dams and Ecosystems: Assessing and Managing Environmental Impacts

Mr. E.A.K. Kalitsi
Volta River Authority, Ghana
Dams and Ecosystems: Assessing and Managing Environmental Impacts (Ghana's Experience)

Construction of dams to create reservoirs is always associated with changes in ecosystems. Assessing and managing the social and environmental impacts of such developments are important in order to ensure that these projects are beneficial. As a result of the Akosombo (1965) and Kpong (1972) Developments, Ghana has significant experience on the assessment and management of the social and environmental impact of dams. This submission discusses the lessons learnt from the experience during the colonial era and at independence, and how they can be used to build the new Bui Development. For example, people displaced from Akosombo have never felt satisfied.

Policies for resettlement and compensation should be developed well ahead of dam construction. All persons adversely affected by the formation of the reservoir should be properly and appropriately compensated in cash and in kind. The resettlement costs should cover all inundated properties including houses, farms and public facilities. The environmental costs should always be factored into the price of electricity in order to reflect the true cost of power. This is essential to sustain the programmes needed to ensure the effective mitigation of environmental effects of the hydro development. To protect the integrity of the lake, measures should be taken to check deforestation by protecting the original forests.

Reservoirs also provide tremendous opportunities for the development of tourism. It is important to match the rate of development to the pace and quality of environmental protection in the area where the project is situated.

The key recommendation is to err on the side of generosity in sharing of benefits, although local affected people are unlikely to be fully satisfied with the compensation package.

Mr. Karim S Numayr
Chairman, National Committee of Large Dams, Jordan
Sedimentation and Water Quality Problems at the King Talal Reservoir

The aim of this submission is to share the experiences related to water quality and sedimentation at the King Talal Reservoir (KTR) in Jordan. It also proposes different phases to address the issues. The KTR was constructed in 1978 and it was designed to store water from river base flow and from sewage treatment plants and effluents from industrial plants between Amman and Zarqa. In addition, it collects the natural runoff from the Zarqa River Basin and some major springs. Water from the KTR is used for agricultural irrigation in the Jordan Valley.

Sedimentation is an issue in the KTR because its rate of accumulation is relatively high and the reservoir storage capacity is reduced. There is also a risk that the sediments can plug the outlet works of the dam and prevent supply to 10 000 ha of irrigated land. Water quality is greatly influenced by the incoming wastewater, which has a high concentration of suspended solids and nutrients such as phosphorus and different nitrogen compounds. The paper proposes three phases to address each issue. For sedimentation it suggests:

1. site investigation and risk analysis
2. engineering design and feasibility, and
3. implementation of work.

For water quality it proposes:

1. assessment and evaluation
2. management and mitigation practices, and
3. budgeting and implementation. This work is underway at present.

The presenter stressed the need to plan and implement the necessary studies and to look at all the options before proceeding, as each path can have environmental and economic consequences.

Ms. Elisabeth Khaka
United Nations Environment Programme, Kenya
Implication of Dams on the Freshwater and Coastal Environment and its Resources in Senegal

Ms. Khaka made the presentation on behalf of UNEP colleagues unable to attend. She referred to the negative downstream environmental implications of dam projects and emphasised the need for integrated water resources management that incorporates coastal regions. One example of this is the impact of land-use systems on downstream and coastal areas. The Senegal River is a case study that indicates the need for comprehensive and systematic water resources management with assessment of environmental and socio-economic conditions of the river basin and its associated coastal region. These two areas represent distinct management systems yet they are inextricably linked.

On the Senegal River, a reduction in fish yields has been observed downstream of the Diama dam as well as an increase in bilharzia in the river itself. The coastline and river has undergone profound geomorphological changes. The inner mouth of the river is dependent on onshore drift and sediment transport from the (now dammed) river. There is therefore a need for a systematic review of the impacts of the dam on the river as well as on the coastal regions and to view them as a single unit. One option for integrated management of river basins and coastal areas is being jointly prepared by UNEP and the Priority Actions Programme Activity Centre for the Mediterranean Action Plan. This set of guidelines is to be tested in Croatia and Bosnia Herzegovina. Ms. Khaka stressed the need for integrated basin planning in dam design and management.

Mr. Mohamed Lemine Ould Baba
Universit‚ de Nouakchott /IUCN-Mauritania, Mauritania
Reducing the Environmental Impacts of the Manantali and Diama dams on the Ecosystems of the Senegal River and Estuary: Alternatives to the Present and Planned Water Management Schemes

In the post-Sahelian drought era (1970s), the governments of Mali, Senegal and Mauritania planned to construct two major dams, the Diama and the Manantali, on the Senegal River. Diama completed in 1986 is located 27 km upstream of the river mouth in Senegal and Manantali (1990) is located in Mali. The objective was irrigating 375,000 hectares of floodplains for rice cultivation, production of hydropower and navigation. Mr Lemine Ould Baba's presentation refers to the Mauritanian side of the delta region.

In the Senegal valley, traditional floodplain agriculture, fertilised by sediments from flood water and cattle dung from dry season grazing, was an important source of livelihood and food security for the rural poor. Irrigated agriculture is confronted with difficulties in the absence of drainage facilities and increasing saline intrusion, lowering rate of expansion and production level (3T/ha/yr as opposed to 12T/ha/yr in project document). The burgeoning population of grain eating birds, in the absence of dry season mortality, hampers agricultural production. A tenacious reed (Typha) that obstructs reservoir fishing has replaced pasture in large areas of the former floodplain. The Sahelian nomadic pastoral communities are affected by reduced dry season pastures. The impact has been devastating for Sporobolus a perennial grass used for weaving by women and serving as a major source of livelihood. Among species going extinct are indigenous variety of water lily used as a cereal substitute by communities and a floating wild rice, compatible with flood plain cultivation.

Mr Lemine Ould Baba emphasised the unpredictable ecosystem and hydrological changes (saline groundwater) following the dam. He recommends that the development approach for the Senegal Valley must account for multiple water uses and involve the affected users and stakeholders in decision-making for operation and mitigation measures. Some of the suggested mitigation measures include the creation of an artificial estuary for preserving mangrove flora and fauna, reducing water level in the reservoir to enable cultivation of dry season crops, regeneration of pasture, and reducing reed invasion. Field trials already underway in Mauritania indicate that such restoration can be successful and is supported by local people who depend on the ecosystem for their livelihood.

Commissioners' question time

Chair:
How local and specific is the sedimentation problem at the King Talal Dam?

Mr. Numayr:
There are different aspects to this problem, such as topographic perspective or type of material or its contents (eg organic matter/chemical). There may be heavy metals that were undetectable and we only found them recently. As far as the biological content of sediments are concerned, it is not high. The main concern now is that it is too close to the outlet works. It may even be inside the intake pipes. We want a diver to go down and video the situation. We have some measurements and the contour lines for the sediments. It is currently 8.7 m above the intake. We may have to dredge(which is costly) and this will also affect the water quality as sediment is disturbed. We do not want sediments to be flushed into the irrigation area either. However, I believe that we are addressing the problem and will solve it.

Commissioner Veltrop:
Considering the loss of reservoir volume of 15%, what is the estimated lifetime of the reservoir and what will be the effect of the remedial works on that life?

Mr. Numayr:
12 million m³ of the 87 million m³ reservoir volume is now filled. In the first expansion we gained 16 million m³. How to extend its life? At construction, it had a 50 years lifetime, built in 1978, therefore we expect it to end in 2030, but with the new raising we have to look again. We may be able to enlarge it with vertical expansion, we may have to do this in both directions if the foundation is ok. As far as the quality is concerned, we may also have to remove the sediments. This is not easy and will be costly also to store the sediments so they don't return to the reservoir. All this must be studied so that we don't lose this dam. Thank you.

Commissioner Blackmore:
With all these sediments coming in, is there any action being taken in the catchment to reduce the loads coming in?

Mr. Numayr:
This is a part of the proposed solution - upstream sediment traps and soil stabilization in some regions. We also had some problems with landslides. The works have to be cost-effective.

Dr. Henderson:
One issue that we are interested in is whether these problems have been anticipated at the planning phase - to what extent were these problems identified.

Mr. Numayr:
I don't have data to answer your question - my feeling is that it was not taken with great care. Now it is being taken care of.

Chair:
This is exceptional as he is not part of this panel, but I give Dr. Haddadin the floor.

Dr. Haddadin:
The last comment is true. The project was started during civil disturbances in 1971 when it was hard to visit the site due to instability, and there was a political will to develop the country and this was the first project after the 1967 war to be decided and started. On your question Chairman, yes, the issue is site-specific as the catchment has no plant cover (it is desert). Yes, there have been measures for land stabilisation, terracing and afforestation - interrupted due to money. The forecast dead storage was 6 million, way below the current loss due to sediment.

Commissioner Moore:
One interest for us is options assessment, and to understand the planning process. For the Bui Dam, are you examining whether the other two dams are working as predicted, and have you looked at other options? How do you assess the value of the National Park, and how do you address these trade-offs in the planning process?

Mr. Kalitsi:
The whole thrust of my paper is that we are taking our experience with Akosombo into account when planning the Bui Dam. For the National Park, for example, we identified the NP, the size of the NP and the impact of this project as a matter of fact there are different heights at which the dam could have been built and the impact for each was studied. The preferred level was adopted for this planning. Because of the importance of the environmental factors we have advertised for proposals for a study into the Bui Dam. This will be based on our experience in the way the dams have performed and the way the reservoir has performed (biologically, sociologically, and economically). Bui has a direct impact on existing reservoirs and these are being studied. The benefits of the National Park are also being assessed - at present it is open to abuse. The limits of the Park should be extended and with better management we can improve things.

Commissioner Patkar:
A comprehensive assessment of impacts on social and environmental issues is needed - what would you suggest as a maximum assessment of appraisal based on those? Would you really suggest an alternative, knowing that mitigation or restoration is not possible, so that certain genuine alternatives can be assessed in the right point of time?

Mr. Ould Baba:
The problem is the loss of the floodplain. What is cultivated needs to be valorised. It's the rest that is important, especially in the lower delta. This restoration since 5-6 years has restored 5 to 6 000 ha of floodplain. The invasion of plants is important and brings health problems. I do not agree it is impossible to restore, and we have relevant examples. For example, we should continue to fluctuate levels of Diama dam to maintain the original social and environmental character of the area. This is very important for the Sahel due to pastoral transhumance.

Summary of panel 4

The panel discussion addressed a range of environmental issues, from planning, through to reservoir management and environmental restoration. The discussion focussed on the following issues :

1. The difficulties in managing unforeseen changes in water quality in reservoirs as a result of changing population dynamics and occupation of the catchment.



2. The need to learn lessons from past experience in order to ensure successful projects in future, one of which is the need for more social and environmental studies during the feasibility phase and the assessment of alternatives.



3. The degree to which sensitive management of the infrastructure can promote environmental rehabilitation in the face of undesirable ecosystem change.



4. Upstream dam projects can have severe implications for the morphology of downstream coastal zones, at the interface between marine and fluvial processes