Feasibility and environmental assessment of hydropower plants

Hydropower is the energy source that requires no fossil fuels and doesn´t present carbon emissions to the environment in its operational stage. Within the global energy framework there is great demand for both types of energy, renewable and non-renewable, and a special interest in the search of undeveloped hydroelectric resources in high potential and the Andean countries.

Feasibility and environmental impact

Feasibility and environmental impact of hydroelectric plants studies involve the following tasks:

 

Potential of generation

A hydroelectric project must begin with the identification of potential sites under certain evaluation criteria; criteria for site selection taking into account topography, water regimes and various factors. Hydropower capacity of a site is based on site characteristics, data flow in rivers and the water column available.

Determination of the water column: Based on the topographical study using Geographic Information Systems (GIS), it can optimize the selection of points with greater water column and minimum distance between the intake and turbines. This regional analysis allows selection of the best locations on a regional scale with less consumption of time.

Determination of flow regime: Based on the existing information and distributed hydrological models average flow, maximum and minimum reservoir of the hydroelectric plant are obtained. These flows will be an entry parameter for the design of the reservoir, the determination of generation capacity and project risk analysis.

 

Hydrogeological aspects

An evaluation of the groundwater regime and its interaction with the reservoir and dam has to be considered in the planning and design of hydroelectric plants.

Loss of flow through the dam abutments and background: Because the reservoirs are supported on a porous alluvium material and fractured rock, it is important to evaluate the hydraulic containment of the dam. Loss of flow can become significant and affect the storage capacity of the dam.

Leak flow rate and piping: Great speed in the flow of groundwater can drag the fine inside the alluvium material and the weathered rock producing the “piping” where preferential flow channels are produced and the subsequent collapse of the material. Dam designers must calculate the maximum speeds in a three-dimensional numerical modeling and suggest corrective actions to slow the leak.

 

Geotechnical aspects

Landslides in the reservoir basin: Growth of water level in the reservoir involves a redistribution of water table in the area of influence of the reservoir. By increasing the water table, the potential for landslides increases. The numerical model of the groundwater regime should be modified by increasing the level of a reservoir for subsequent geotechnical evaluations.

 

Environmental aspects

There is a concern for preserving the environment so environmental considerations must also be evaluated in the selection process and planning.

Determination of environmental flow: hydroprojects often involve changes in natural flow fluctuations in water courses. There is an effect of flow regulation on fish and aquatic flora in the bed of the river so the river drainage produced by flow regulation could have an adverse impact.

Salinization of floodplain: Due to the absence of flow in rivers, saturated soils on banks of rivers begin to evaporate into the environment and create salt crusts. This process of salinization is not friendly to the environment and reduces flora and fauna in the ecosystem of the bed of the river. Environmentalists should calculate the potential of salinization in the river bed due to the installation of a hydroelectric plant.

 

Project management aspects

Climate, hydrological and hydrogeological Monitoring system design: Few data availability limits hydrological evaluations of river flows and how they are treated; the reduction of data redundancy generates confidence in the estimates of developable hydropower capacity. Managers should take into account design of environmental monitoring systems at different stages of the proposed hydrological stations serving tools for assessments of generation capacity, reservoir management and identification of environmental problems.

Risk analysis of critical infrastructure: Due to the extension of a hydroelectric project and its relation to the water cycle, there are aspects of risk analysis of floods and droughts that have to be incorporated into the planning and design production capacity infrastructure.

Sedimentation in the bed of the reservoir: The potential for sedimentation of natural flow of a river should be incorporated into the design of the project’s life. Engineers must calculate sedimentation rates in reservoirs and evaluate alternative solutions.

Saul Montoya

Saul Montoya es Ingeniero Civil graduado de la Pontificia Universidad Católica del Perú en Lima con estudios de postgrado en Manejo e Ingeniería de Recursos Hídricos (Programa WAREM) de la Universidad de Stuttgart con mención en Ingeniería de Aguas Subterráneas y Hidroinformática.

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