Integrated modelling of a new dam: a case study from the "HELP" Mesta/Nestos River

New important dam projects and multipurpose water reservoirs are important parts of water resources management at the river basin scale in order to satisfy water needs in different sectors, such as hydroelectricity, water supply and agriculture. In an era of open market economy, investments for new dam projects are no longer covered by state budgets; so they need to attract private investment and thus should be able to demonstrate economic reliability and beneficial returns during their lifetime (usually 50 years). Apart from economic considerations, water managers should also apply the main principles of integrated water resources management at the river catchment scale, which are included in new regulations for environmental protection, public participation and social equity. For example, the European Union Water Framework Directive (EU-WFD) stipulates that water resources management should combine economic issues together with technical reliability in order to meet environmental and social objectives. In this paper, an integrated model for a new dam project which allows these objectives to be met is described. The model was applied in the case of the "Temenos" dam located in the Greek part of the transboundary river Mesta/Nestos. The basin covers 6,218 km(2) and is almost equally divided between Bulgaria and Greece. It flows from the North, where the headwaters are located in the Rila and Pirin mountains of Bulgaria, to the South East, where the river ends in a delta situated on the coast of the Aegean sea in Northern Greece. Currently, two hydroelectric power plants are located in the mountainous part of the Nestos basin in Greece: the Thissavros plant, with a reservoir capacity of 565 millions m(3), and further downstream the Platanovryssi dam, with a reservoir capacity of 11 millions m3. Both dams were designed to operate in pump-storage mode for electricity generation. The future Temenos project is planned to be financed exclusively by private funds. Situated downstream of the other two dams, it is designed for electricity production, irrigation regulation and should contribute to increasing the total amount of power produced by the existing complex. The integrated model of the Temenos project is based (1) on the MODSUR distributed hydrological model, (2) the HEC-ResSim tool for reservoir simulation, (3) the CLM regional climate model from the Max Planck Institute for Meteorology, Germany, and (4) the use of a special purpose economic tool based on the NPV (Net Present Value) rule. Different climate scenarios were generated and used for testing the viability of the Temenos project, together with transboundary assumptions based on the execution of the flow treaty between Bulgaria and Greece on the sharing of the Mesta-Nestos waters. The economic rule has been extended to include the merging of economic elements (energy and water selling prices) with social benefits (compensation to farmers in case of lack of water) and the value of the environment (costs for restoration of good water status in case of failure to preserve a minimum environmental flow). It is argued that this integrated approach offers water managers and stakeholders a useful evaluation of the sustainability of water projects.