Flow Regime Changes: From Impounding a Temperate Lowland River to Small Hydropower Operations

Petras Punys,Egidijus Kasiulis,Gitana Vyčienė,Linas Šilinis,Antanas Dumbrauskas

doi:10.3390/en8077478

Abstract

This article discusses the environmental issues facing small hydropower plants (SHPs) operating in temperate lowland rivers of Lithuania. The research subjects are two medium head reservoir type hydro schemes considered within a context of the global fleet of SHPs in the country. This research considers general abiotic indicators (flow, level, water retention time in the reservoirs) of the stream that may affect the aquatic systems. The main idea was to test whether the hydrologic regime has been altered by small hydropower dams. The analysis of changes in abiotic indicators is a complex process, including both pre- and post-reservoir construction and post commissioning of the SHPs under operation. Downstream hydrograph (flow and stage) ramping is also an issue for operating SHPs that can result in temporary rapid changes in flow and consequently negatively impact aquatic resources. This ramping has been quantitatively evaluated. To avoid the risk of excessive flow ramping, the types of turbines available were evaluated and the most suitable types for the natural river flow regime were identified. The results of this study are to allow for new hydro schemes or upgrades to use water resources in a more sustainable way.

Highlights

Humans often modify rivers to meet specific objectives, including hydropower generation
Small hydropower plants (SHP) cannot be treated as a scaled down version of the large dams
The results indicate that flow variability statistics should be quantified using subdaily datasets to accurately represent the nature of hydropower operations, especially for daily peaking facilities

Summary

Introduction

Humans often modify rivers to meet specific objectives, including hydropower generation. Flexibility in the timing of water use is a primary reason for regulating rivers. It is accepted that the construction of dams causes hydrologic alterations with consequent changes in ecological conditions. The effect of the impact depends on many factors and has to be considered on a case by case basis. Irrigation dams have completely different hydrologic alterations than hydropower operations. The vast majority of studies considering these issues are based on large hydropower plants (HP) or large dams, where impacts are obvious. Small hydropower plants (SHP) cannot be treated as a scaled down version of the large dams. A literature review has shown that there is a lack of associated studies, especially for low to medium head facilities operating in temperate lowland rivers

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Results