Assessment of the Impact of Small Hydropower Plants on the Ecological Status Indicators of Water Bodies: A Case Study in Lithuania

Abstract

Hydropower plants produce renewable and sustainable energy but affect the river’s physico-chemical characteristics and change the abundance and composition of the aquatic organisms. The impact of large HPPs on the ecological conditions of surface water bodies have been extensively studied, but less attention has been paid to environmental impact studies of small hydropower plants (SHPs). The impact of hydropeaking on both the river flow regime and ecosystems has been well-studied for peaking mode plants, mainly medium to large-sized ones. However, for small hydroelectric power plants, and especially for those in lowland rivers, the available information on water quality, benthic macroinvertebrates communities and fish abundance, and biomass is not sufficient. Ten small hydropower plants were selected, and the ecological status of water bodies was assessed in different parts of Lithuania. The studies were performed at the riverbed upstream from the SHPs, where the hydrological regime has not changed, and downstream from the SHPs. It was found that the small hydropower plants do not affect the physico-chemical values of the water quality indicators. This study demonstrated that the total number of benthic macroinvertebrates taxa (TS) is influenced by the concentration of nitrogen and suspended solids, the water flow, the river area, and the current speed; the number of EPT (Ephemeroptera (mayflies), Plecoptera (stoneflies), and Trichoptera (caddisflies)) taxa is influenced by the concentration of nitrogen and suspended solids. The studied indicators do not have a significant impact on biomass. The SHPs affect the fish abundance and biomass. The Lithuanian fish index (LFI) is influenced by the average depth and area of the river. Some SHPs operating in lowland areas may yield somewhat significant hydrograph ramping but more detailed investigation is needed to support the significance of this impact on the biological indices.

Analysis of Hydrologic Regime Changes Caused by Small Hydropower Plants in Lowland Rivers

“…The changes in the rates of flow variation were mentioned among most common and noticeable by Magilan and Nislow [18] and Ely et al [27]. Since the present study was based on daily flow data, it was not possible to compare the results with those of Punys et al [12] andČesonienė et al [48], which used sub-daily (hourly) flow data and identified a significant flow hydrograph ramping downstream from some studied HPP dams. However, the findings of [48] showed that the ramping did not correlate to a significant impact on the biological indices.…”

“…Since the present study was based on daily flow data, it was not possible to compare the results with those of Punys et al [12] andČesonienė et al [48], which used sub-daily (hourly) flow data and identified a significant flow hydrograph ramping downstream from some studied HPP dams. However, the findings of [48] showed that the ramping did not correlate to a significant impact on the biological indices. Still, such a rapid and frequent flow and stage fluctuation certainly indicate a high undesirable, unnatural modification of the flow regime.…”

Impact of a small hydropower plant on water quality dynamics in a diversion and natural river channel

“…The magnitude of change from above and below the hydropower plants ranged from −69.09 to +24.25%. Studies of physicochemical parameters have also been carried out at other hydropower plants, including run‐of‐river hydropower plants; however, due to their scope or the lack of available data, it was not possible to determine WQIs for them (e.g., Fantin‐Cruz et al., 2015; Česonienė et al., 2021; Alvarez et al., 2020; Valero 2012; Vaikasas et al., 2015; Tomczyk & Wiatkowski, 2021).…”

“…Instead, the research focus is usually on hydroelectric plants in large reservoirs (e.g., Fantin-Cruz et al, 2015;Wang et al, 2016;Zhao et al, 2020). Previous research on this topic has found that these plants had the most significant effect on the richness and structure of the ichthyofauna and benthos (Bidoglio et al, 2019;Silverthorn et al, 2018;Álvarez et al, 2020;Česonienė et al, 2021), river continuity (a hydropower plant acts as a transverse obstacle on the path of migration of organisms and causes habitat fragmentation) (Jumani et al, 2019;Gibeau & Palen, 2020;Puzdrowska & Heese, 2019), hydrologic conditions (changes in the amplitudes of fluctuations in the state, daily and annual flows, and the values of these parameters) (Alipour et al, 2020;Ding et al, 2019;Kucukali, 2014), accumulation and erosion of bottom sediments (Anderson et al, 2015;Isaac & Eldho, 2019), and the physicochemical composition of these sediments and water (especially within the context of nutrients and heavy metals, which are highly concentrated within the sediment) (Chen et al, 2018;Fantin-Cruz et al, 2016;Wu et al, 2018).…”

Run-Of-River Small Hydropower Plants as Hydro-Resilience Assets against Climate Change

“…ROR SHPPs, on the other hand, are more so considered as hydro-resilience facilities with minimum dependence of hydraulic head variations [78], as well as installations that could produce energy even in low flows. As friendlier projects with fewer impacts on the environment, e.g., non-affection of the physico-chemical values of the water quality indicators [79], ROR SHPPs have been gaining interest from policymakers and investors during the last few decades [35], with sustainability indicators for ROR hydroplants to be presented in the literature [80].…”