Assessing the impact of climate change and extreme value uncertainty to extreme flows across Great Britain

Floods are the most common and widely distributed natural risk, causing over £1 billion of damage per year in the UK as a result of recent events. Climatic projections predict an increase in flood risk; it becomes urgent to assess climate change impact on extreme flows, and evaluate uncertainties related to these projections. This paper aims to assess the changes in extreme runoff for the 1:100 year return period across Great Britain as a result of climate change using the Future Flows Hydrology database. The Generalised Extreme Value (GEV) and Generalised Pareto (GP) models are automatically fitted for 11‐member ensemble flow series available for the baseline and the 2080s. The analysis evaluates the uncertainty related to the Extreme Value (EV) and climate model parameters. Results suggest that GP and GEV give similar runoff estimates and uncertainties. From the baseline to the 2080s, increasing estimate and uncertainties is evident in east England. With the GEV the uncertainty attributed to the climate model parameters is greater than for the GP (around 60% and 40% of the total uncertainty, respectively). This shows that when fitting both EV models, the uncertainty related to their parameters has to be accounted for to assess extreme runoffs

Morphological sustainability of barrage impoundments

Barrages built in estuaries fundamentally alter the dynamics of the river with regard to both flow and sedimentation patterns. Therefore it is essential to ensure that these structures do not affect the sustainability of the systems in which they are built. In recent years there has been increased emphasis on assessing the effect of climate change on river flows and the impact that this has on watercourses. Therefore, to investigate morphological sustainability of barrage impoundments, the effect of climate change must be included. An assessment of the morphological sustainability of the River Tees impoundment is presented. The predictions were completed using the l-dimensional software package ISIS, which modelled flow and sediment movement within the impoundment. Fifty-year simulations were completed to predict the sediment distribution through the system under differing future scenarios. A method is proposed for extending the flow boundary for the numerical model, which uses a generic statistical modelling technique. It uses the historical flow data recorded on the Tees and forward predicts the series based on its statistical properties. Firstly, the Markov Chain method was used to predict a 50 year flow series which assumes a stable climate. The predicted series showed good correlation with the measured series in terms of both statistical properties and structure. Secondly, the method was further developed to enable climate change predictions to be incorporated. This means that the generated series can be modified to directly account for the possible influence of climate change on discharge. This technique uses a Markov model fitted in the framework of a multinomiallogit model, enabling catchment precipitation and temperature values to be linked to the discharge. Climate change predictions available for the period 2070 to 2100 were then used to create 50-year modified flow series for the River Tees under a medium\high and medium\low emissions scenario. During the period of sediment monitoring on the Tees a change to the sediment supply was noticed as a result of the high flows experienced in October/November 2000. Unfortunately, it is unclear whether the sediment supply will return to its original levels or if, as a consequence of higher flows resulting from climate change, the supply will remain at present levels. Hence three different sediment rating curves were created from the field data to deal with this uncertainty; representing high, medium and low sediment supply conditions. Using the data generated for the flow and sediment boundaries, simulations were undertaken to assess the morphological sustainability of the Tees impoundment. Simulations using a flow boundary, which assumed both a stable climate and a changed climate, as well as three different sediment supply options for each, were considered. The results show that the impoundment reaches a dynamic equilibrium during the modelled period, irrespective of the sediment supply. From this it is possible to state that the Tees Impoundment is morphologically sustainable over the next 50-80 years. Climate change, while increasing the sediment supply, actually appears to improve the sustainability of the impoundment with regards to sediment. The increased number of high flows cause more steep water surface slopes which reentrain sediments and partially flush the system. In conclusion this thesis presents an assessment of the morphological sustainability of the Tees impoundment under differing future climate scenarios for both the fluvial and sediment inputs. Within the course of the work a different technique for extending flow series assuming both a stable and changed climate has been proposed. It is hoped that these methods will be of use in future sustainability assessments; however further investigations into these methods would be beneficial

Assessment of freshwater ecosystem services in the Beas River Basin, Himalayas region, India

River systems provide a diverse range of ecosystem services, examples include: flood regulation (regulating), fish (provisioning), nutrient cycling (supporting) and recreation (cultural). Developing water resources through the construction of dams (hydropower or irrigation) can enhance the delivery of provisioning ecosystem services. However, these hydrologic alterations result in reductions in less tangible regulating, cultural and supporting ecosystem services. This study seeks to understand how multiple impoundments, abstractions and transfers within the upper Beas River Basin, Western Himalayas, India, are affecting the delivery of supporting ecosystem services. Whilst approaches for assessing supporting ecosystem services are under development, the immediate aim of this paper is to set out a framework for their quantification, using the macroinvertebrate index Lotic-Invertebrate Index for Flow Evaluation (LIFE). LIFE is a weighted measure of the flow velocity preferences of the macroinvertebrate community. Flow records from multiple gauging stations within the basin were used to investigate flow variability at seasonal, inter-annual and decadal time scales. The findings show that both mean monthly and seasonal cumulative flows have decreased over time in the Beas River Basin. A positive hydroecological relationship between LIFE and flow was also identified, indicative of macroinvertebrate response to seasonal changes in the flow regime. For example, high LIFE scores (7.7–9.3) in the winter and summer seasons indicate an abundance of macroinvertebrates with a preference for high flows; this represents a high potential for instream supporting ecosystem services delivery. However, further analysis is required to understand these hydroecological interactions in the study basin and the impact on instream supporting ecosystem services delivery

Towards intangible freshwater cultural ecosystem services: informing sustainable water resources management

Rivers provide a range of Cultural Ecosystem Services (CES) such as aesthetic values, sense of place and inspiration, which remain insufficiently studied due to challenges associated with the assessment of their subjective and intangible attributes. However, the understanding of CES remains important as they are strongly linked to human wellbeing. This study utilizes a questionnaire-based survey to capture views from two villages along the mainstream of the Beas River in India, to identify the CES it provides, to assess how local communities appreciate their importance and how they relate to river flows. In total, 62 respondents were interviewed. Findings show that the Beas River provides several CES but among these, spiritual/religious ceremonies and rituals, aesthetic values and inspiration benefits were indicated as absolutely essential to the local communities. Results also demonstrate that people’s perception of the quality of CES is sometimes linked to river flows. It can be concluded that the Beas River is crucial in the functioning and livelihoods of local communities as it lies within the core of their cultural, religious and spiritual practices. This study reinforces the need to consider the full suite of ecosystem service categories in sustainable water resources development, planning and decision makin

Towards Intangible Freshwater Cultural Ecosystem Services: Informing Sustainable Water Resources Management

Rivers provide a range of Cultural Ecosystem Services (CES) such as aesthetic values, sense of place and inspiration, which remain insufficiently studied due to challenges associated with the assessment of their subjective and intangible attributes. However, the understanding of CES remains important as they are strongly linked to human wellbeing. This study utilizes a questionnaire-based survey to capture views from two villages along the mainstream of the Beas River in India, to identify the CES it provides, to assess how local communities appreciate their importance and how they relate to river flows. In total, 62 respondents were interviewed. Findings show that the Beas River provides several CES but among these, spiritual/religious ceremonies and rituals, aesthetic values and inspiration benefits were indicated as absolutely essential to the local communities. Results also demonstrate that people’s perception of the quality of CES is sometimes linked to river flows. It can be concluded that the Beas River is crucial in the functioning and livelihoods of local communities as it lies within the core of their cultural, religious and spiritual practices. This study reinforces the need to consider the full suite of ecosystem service categories in sustainable water resources development, planning and decision making