1. Context and Mandate of the World Commission on Dams

1.1 The World Commission on Dams (WCD) was established to address central issues of the controversy with respect to decision-making about large dams and their effectiveness in sustainable development. The Commission's overarching goals are:

• To review the development effectiveness of dams and assess alternatives for water resources and energy development
• To develop internationally acceptable standards, guidelines and criteria for decision making in the planning, design, construction, monitoring, operation and decommissioning of dams.

1.2 The WCD work programme is composed of four sets of activities that will generate the comprehensive base of shared knowledge needed to produce these three major outputs:

• 8-10 in-depth case studies of specific dams in the river basins in which they are located
• A cross-check survey of 150 dams world-wide
• 17 thematic reviews of cross-cutting issues that are at the core of the dams' debate
• Solicited and submitted inputs from interested individuals and organisations

2. The Cross-Check Survey

2.1 Objectives:

As an integral part of the work programme, a cross-check survey of approximately 150 large dams will be conducted. The sample of 150 will be constructed from focal and non-focal dams in the river basins of the WCD case studies, from dams that have been previously analysed in other studies or for which data is available in existing databases, and from complementary dams that contribute to the overall diversity of the sample.

The analysis of this sample will seek to generate broader patterns and trends relating to the performance (e.g. the extent to which dams in the sample that have achieved their project objectives) and decision-making aspects (e.g. the percentage of projects for which certain criteria and guidelines were required and conducted) of dams. The cross-check survey results will, however, only be illustrative of past experience rather than representative of all of the large dams that have been built world-wide.

2.2 Scope

A variety of dams of different types (e.g. storage, run-of-river); ages (e. dams from the 1930's through the 1990's), functions (e.g. water supply, irrigation, power, flood management, recreation and other); ownership structures (e.g. public, corporate and private); and regional locations will be included in the cross-check survey. Each dam will have a date record with time series dimensions where feasible. Analysis will be performed on the full set and on sub-sets of 150+ dams in the sample.

The cross-check survey is not intended to provide conclusions on the acceptability of individual projects. Rather, the conclusions will be of two kinds. First, patterns or frequencies across the sample for performance issues such as projected versus actual electricity generated, projected versus actual increases in agricultural production, projected versus actual costs, etc., will be identified. Second, trends over time such as the percentage change in projects undergoing environmental impact assessments as part of the project cycle and whether they were part of part of a river basin master plan will be derived.

2.3 The Sample

The sample of 150 large dams has been constructed to maximise the value of the findings than can be derived from the cross-check survey. Given the time and resources available to the WCD, as well as other constraints, the construction of a fully representative sample of the total population of large dams is not possible. Nevertheless, the cross-check survey will be quite comprehensive and is likely the most extensive ever conducted on large dams.

The sample of 150 large dams for the cross-check survey is composed of the following sub-samples:

• 8 focal dams from the case studies;
• approximately 27 non-focal dams from the river basins in which the case studies are located (a maximum of 5 per basin not including the focal dam will be selected) because of relatively easy access to data on these dams;
• approximately 30 dams from existing databases or where information is readily available such as the World Bank Operations Evaluation Department, International Rivers Network, International Energy Authority, etc. because of relatively easy access to data on these dams;
• approximately 60 additional dams to add geographical, temporal, functional and size diversity to the sample of 150.

2.4 Data Collection Instruments

A data collection questionnaire has been developed by the Secretariat for the dams in the cross-check survey. These cross-check survey data-collection sheets primarily focus on questions that will yield:

a) predicted versus actual measures of benefits, costs and impacts of dams;
b) descriptive parameters mainly related to decision-making of dams.

Consistency of results will be increased because the standardized data-collection questionnaire sheets will be employed for all 150 dams. However, it is likely that not all data will be available for all 150 dams. The analysis of the cross-check survey will faithfully record the impact of data gaps on the findings where relevant.

2.5 Data Collection Procedure

Data for the focal and non-focal dams will be collected in conjunction with the execution of the WCD case studies, while information for dams drawn from other databases will need to be supplemented and verified. Commissioned consultants will collect the data for the additional 60 large dams.

The approach for developing the data records for the cross-check large dams will include research of published reports and secondary data sources available in the public domain, as well as contact with the following types of organisations requesting information:

• dam operators and utilities;
• key government departments responsible for the project (e.g. Ministry / Department of Irrigation / Power of State or National government; or appropriate river basin development authority);
• local institutions/universities that may have conducted research on the dam;
• local NGO's/networks working on dams at the state / national level;
• NGO's/networks with a regional and/or international focus on dams issues;
• industrial/engineering firms with international experience and involvement in dams (with permission of the host country);
• multilateral and bilateral agencies for data on large dams available with them;
• international professional associations (ICOLD, ICID, IHA, IEA) with access to data.