Conceptual Modelling to Assess Hydrological Impacts and Evaluate Environmental Flow Scenarios in Montane River Systems Regulated for Hydropower

Abstract

To improve understanding of natural and managed flow regimes in data‐sparse regulated river systems in montane areas, the commonly used Hydrologiska Byråns Vattenbalansavdelning (HBV) conceptual run‐off model was adapted to incorporate water regulation components. The extended model was then applied to the heavily regulated river Lyon (391 km2) in Scotland to reconstruct the natural flow regime and to assess the impacts of regulation at increasing spatial scales. Multi‐criteria model evaluation demonstrated that the model performed well in capturing the dominant catchment processes and regulation effects, especially at the timescales at which operation rules apply. The main change as a result of regulation in the river Lyon is a decrease in inter‐annual and intra‐annual variability of all elements of the flow regime, in terms of magnitude, frequency, and duration. Although these impacts are most pronounced directly downstream of the impoundments, the regulation effects propagate throughout the river system. The modelling approach is flexible and widely applicable and only limited amounts of data are required. Moreover, results are easily communicated to stakeholders. It has the potential to contribute to the development of flow regimes that may be more beneficial to the ecological status of rivers. In the case of the river Lyon, it is likely that this involves a more variable release regime. The approach developed here provides a tool for assessing impacts on flow regimes and informing environmental flows in other data‐sparse regions with heavily regulated montane river systems. Copyright © 2014 John Wiley & Sons, Ltd.

Metrics to assess how longitudinal channel network connectivity and in‐stream Atlantic salmon habitats are impacted by hydropower regulation

“…It is assumed that all barriers are fully passable in the downstream direction. Further details of the Tay and Lyon catchment areas and regulation schemes are reported by Birkel et al (), Geris et al (), and Soulsby et al ().…”

“…Owing to its glacial history, the catchment has steep hillslopes and tributary streams, with a wide gently sloping valley bottom. Hydropower infrastructure was developed in the 1950s; since then, the river has been heavily regulated for hydropower (Geris et al, ; Soulsby, Birkel, Geris, & Tetzlaff, ), and so, in addition to natural semi‐passable barriers (i.e., waterfalls that are passable under certain conditions), there are a number of manmade barriers to fish migration (i.e., dams; Figure a). Passability of barriers is based on the Scottish Environmental Protection Agency dataset on barriers to fish migration (Table ).…”

Misrepresentation and amendment of soil moisture in conceptual hydrological modelling

“…There are common features among conceptual hydrological models as demonstrated by PDM (Moore, 2007), ARNO (Todini, 1996), HBV (Geris et al, 2014), and Xinanjiang (XAJ) (Zhao, 1980;1992;Zhao and Liu, 1995), such as using multi-bucket concepts, and unrealistic modelling of their soil moisture (e.g., their maximum soil moisture is set at the field capacity).…”

Assessment of streamflow decrease due to climate vs. human influence in a semiarid area

“…Their results indicated that human activities, such as the expansion of agricultural areas, dam construction, and industrial activities, were responsible for more than 50% of the streamflow reduction in the basin (Wang et al, 2013). Geris et al (2015) employed the HBV model to investigate the flow regime variation (i.e., magnitude, frequency, and duration) in a highly regulated catchment in the River Lyon, Scotland. The aim was to develop a model applicable to highly regulated areas and data-sparse regions.…”

“…The aim was to develop a model applicable to highly regulated areas and data-sparse regions. The results indicated that the flow regime had reduced in magnitude, frequency, and duration, at both inter-and intra-annual scales, due to regulation activities in the catchment (Geris et al, 2015). In a study conducted by Birhanu et al (2019), the HBV model was applied to the Gumara catchment's water system in Ethiopia to assess the impact of land use and land cover change on the water cycle and, more specifically, streamflow variation.…”