Simulating and visualising the hydrological and landscape impacts of reservoir engineering at Crummock Water, England

Abstract

The Earth’s 57,000 large water reservoirs have significant impacts on hydrology and landscapes. Meanwhile, environmental degradation is destabilising the climate, ecosystems, and hydrological functionality. In Europe and North America, landscape-scale environmental management schemes are being proposed, including reservoir decommissioning to rehabilitate river catchments. Yet, some proposed schemes have failed due to poor stakeholder engagement and shifting environmental baselines. This research has developed novel approachesto address these issues. It has applied these to Crummock Water raised lake in England, where United Utilities and the Environment Agency are investigating the feasibility of removing infrastructure to renaturalise the lake and the River Cocker. The hydrological impacts of anthropogenic modifications in Crummock Water’s catchment were assessed using existing data, expanded hydrometric monitoring, hydrological modelling, and archival research. Circa 1880, Crummock Water’s outlet was excavated and two timber weirs installed to control outflows. In 1903, the extant masonry weir was built, raising the lake level ~0.6 m. Abstraction reduces lake levels, which necessitates sluice operations to maintain outflows during dry periods, causing further drawdown. Hydrological models of reservoircontaining catchments should include reservoir processes. SHETRAN 4.5 (‘Reservoir’)software was developed to integrate reservoir structures and operations into a physically-based, spatially-distributed hydrology model. A SHETRAN-Reservoir model of the Crummock Water catchment substantially outperformed a SHETRAN-Standard model, particularly during and after dry periods. Several reservoir decommissioning scenarios were constructed. Simulations indicate that decommissioning would ameliorate drawdown of Crummock Water and make the River Cocker’s flow regime more dynamic. The simulated landscape impacts of reservoir engineering at Crummock Water were shown in the context of long-term catchment evolution using 4D landscape visualisation. The catchment’s evolution was conceptualised, before being digitally reconstructed and rendered using GeoVisionary software. The resulting 4D landscape model spanned 14,000 years, from the last Ice Age to (simulated) renaturalisation scenarios in 2030. The effects of 4D landscape visualisation on stakeholder attitudes were investigated, using surveys and workshops with 45 participants in two treatments (‘long’ and ‘short’ visualisation). It was hypothesised that ii presenting extended landscape evolution information would change (H1) stakeholder beliefs around catchment naturalness, and (H2) attitudes towards reservoir renaturalisation. Results showed that the workshops changed both beliefs and attitudes towards renaturalisation. Furthermore, the extended evolution information had a statistically significant effect on attitudes (H2), but not on beliefs (H1). This EngD has developed tools to support decision-making in reservoir engineering and landscape-scale environmental projects: firstly, hydrological and landscape models to show the impacts of reservoir decommissioning at Crummock Water; secondly, a generic freelyavailable physically-based, spatially-distributed modelling package for simulating the hydrological impacts of reservoir operations; thirdly, a new approach to visualising simulated hydrological changes, such as lake levels, and landscape evolution in 4D, and; fourthly, an approach to visualising proposed environmental management schemes in the context of longterm landscape evolution, to reset shifting environmental baselines. Finally, the research findings have been synthesised into a landscape visualisation development framework to support enhanced stakeholder engagement in future landscape-scale projects.