Thermopeaking in Alpine streams: event characterization and time scales

Abstract

The present study provides a detailed quantification of the 'thermopeaking' phenomenon, which consists of sharp intermittent alterations of stream thermal regime associated with hydropeaking releases from hydroelectricity plants. The study refers to the Noce River (Northern Italy), a typical hydropower-regulated Alpine stream, where water stored in high-altitude reservoirs often has a different temperature compared with the receiving bodies. The analysis is based on a river water temperature dataset that has been continuously collected for 1 year at 30-min intervals in four different sections along the Noce River. A suitable threshold-based procedure is developed to quantify the main characteristics of thermopeaking, which is responsible for thermal alterations at different scales. The application of Wavelet Transform allows to separately investigate the thermal regime alterations at sub-daily, daily and weekly scales. Moreover, at a seasonal scale, patterns of 'warm' and 'cold' thermopeaking can be clearly detected and quantified. The study highlights the relevance of investigating a variety of short-term alterations at multiple time scales for a better quantitative understanding of the complexity that characterizes the river thermal regime. The outcomes of the analysis raise important interdisciplinary research questions concerning the effects of thermopeaking and of the related short-and medium-term effects on biological communities, which have been rather poorly investigated in ecological studies.

Attractiveness of a lateral shelter in a channel as a refuge for juvenile brown trout during hydropeaking

“…The risk of drift for aquatic organisms is strongly affected by the morphological condition of the river and the density of refuges (Young et al 2011). Water is turbinated through the powerhouses directly from reservoirs; thus, in the winter, a rapid increase in discharge occurs in combination with a sudden increase in water temperature, which influences the behavior of invertebrates (Carolli et al 2012;Zolezzi et al 2011). Bruder et al (2012 reported that brown trout have difficulty moving up in the Alpine Rhine in a high speed flow and that the fish try to reach shelters to conserve energy.…”

Uncertainty Estimation and Evaluation of Shallow Aquifers’ Exploitability: The Case Study of the Adige Valley Aquifer (Italy)

“…The hydrology of the Adige catchment (9700 km 2 at Trento), is mainly controlled by snow and glacier melting (e.g., [47][48][49]), although it is also significantly influenced by anthropogenic activities such as hydropower production [50] and agriculture [48]. The catchment is characterized by a sub-alpine climate with a long-term mean annual precipitation of 1022 mm.…”

“…Three important tributaries join the Adige River within the study area ( Figure 1A). The Noce River has a mean water discharge of 46 m 3 /s and a timing strongly modified by four hydropower plants located within its catchment [50]. From entrance in the Adige valley, it flows for 11 km before joining the Adige River.…”

Contributions from limnology to reservoir management

“…La distancia necesaria para la recuperación del ciclo térmico diario depende de la velocidad del río, caudal, anchura y procesos de intercambio de calor con la atmósfera (Prats et al, 2012). En algunos casos, además, las variaciones bruscas de caudal pueden conllevar cambios térmicos bruscos que pueden afectar a las poblaciones de macroinvertebrados (Zolezzi et al, 2010).…”