During the last two winters, and that of 2000-01, Chalk catchments of southern England experienced severe groundwater flooding. Rising groundwater tables caused rivers to flow high up-catchment in normally dry valleys, flooding homes and businesses in these locations and further downstream. Groundwater ingress into the sewer network led to restricted toilet use and the overflow of diluted, but untreated sewage to road surfaces, rivers and water courses. Increased sewer flows reaching sewage treatment works caused overspills and the contamination of water flowing into rivers. The water and sewerage company Thames Water Utilities Ltd (TWUL) estimate that they spent in the region of £19m responding to the extreme wet weather of 2013-14 and used a fleet of over 100 tankers. However, the magnitude of the event was so large that these efforts could not stop the discharge of sewage to the environment. A particular challenge in managing groundwater flooding in Chalk catchments is that it can last for weeks to months as they are slow to drain after rainfall stops. In response to these groundwater flooding events TWUL are working to reduce the infiltration of groundwater from the Chalk into sewers, and to understand the risk of groundwater flooding to the network. This involves the development of "Infiltration Reduction Plans", which will be submitted to the Environment Agency, and strategic planning of investment in their infrastructure. This project brings together researchers from the British Geological Survey and Imperial College London, to work in partnership with TWUL infrastructure managers and technical specialists to support this investment planning. The overarching aim of the work is to quantify the scale of the risk of groundwater-induced flooding to the sewer network in a Chalk catchment and to translate this knowledge into options for investment planning. The project builds on recent NERC funded research involving the partners that has developed a series of highly relevant datasets, tools and models. Specifically, we will: (i) quantify the risk of groundwater flooding under current climate using an ensemble of weather sequences generated using the state-of-the art weather generator, GlimClim; (ii) assess changes in the likelihood of flooding under future climate using new probabilistic climate projections; (iii) investigate the propagation, in space and time, of the interaction of groundwater flooding with the sewer network, and where investment should be targeted first to minimise sewer overloading; and (iv) translate this improved understanding into TWUL's investment planning, for example, as part of Ofwat's Asset Management Planning 5-year cycle. The project will use the River Lambourn, Berkshire, which has been impacted by these issues, as a case-study catchment.

Manufactured chemicals are essential for the maintenance of public health, food production, and quality of life, including a diverse range of pharmaceuticals, pesticides, and personal care products. The use of these compounds throughout society has led to increasing concentrations and chemodiversity in the environment. Whilst there has been a focus on understanding the impacts of chemicals on a subset of freshwater biodiversity (particularly invertebrates and fish), we understand less about how chemical pollution impacts freshwater microbes. These microbial communities (the 'microbiome') number in the millions to billions of cells per milliliter of water or gram of sediment and form the most biodiverse and functionally important component of freshwater ecosystems. The biogeochemical and ecological functions delivered by freshwater microbes are essential to wider freshwater ecosystem health. The PAthways of Chemicals Into Freshwaters and their ecological ImpaCts (PACIFIC) project will focus on understanding the link between sources of anthropogenic chemicals and their pathways, fate and ecological impacts in freshwater ecosystems, with an emphasis on freshwater microbial ecosystems and the functions they perform. We will investigate the relationship between predicted diffuse and point source chemical pathways and measured chemical concentrations in water and sediments at locations across the Thames and Bristol Avon catchments, chosen to represent gradients of diffuse pollution sources. These locations will be chosen to coincide with Wastewater Treatment Works (WwTWs) to understand how sewage effluent contributes to chemical burden across these gradients. Liquid chromatography coupled with (high resolution) tandem mass spectrometry and QTOF (quadrupole Time-of-Flight) mass spectrometry will be used to perform targeted and untargeted profiling of chemical groups proven and suspected to impact freshwater ecology. A range of microbial community ecosystem endpoints will also be measured at each location to identify the impact of chemical exposure, including bacterial and fungal community composition via DNA sequencing, the expression of nutrient cycling and chemical stress and resistance genes, the production of extracellular enzymes involved with biogeochemical cycling, and the functional gene repertoire of whole microbial communities. We will perform experimental microcosm exposures on freshwater microbial communities, with increasing complexity and realism, deploying high-throughput screening to identify novel chemical groups (and their structural features) with the capacity to restructure these communities. Exemplar microbial community modifying chemicals will be investigated in more detail by applying cutting-edge molecular techniques to determine ecological exposure thresholds that represent different taxonomic and functional aspects of freshwater microbial ecosystems. Novel field-based mesocosms will be used to explore wastewater exposures in more realistic, but controlled settings, allowing us to explore how chemical pollution may interact with other ecological drivers such as nutrients and temperature, and how microbial responses scale up to higher trophic levels and alter ecosystem functioning. Spatially and temporally up-scaled models of diffuse and point source chemical pollution pathways will be combined with novel thresholds developed from the lab and field exposures, to determine chemical threats to freshwater microbes, supporting the development of tools for the better management of the risks of chemical pollution to freshwater ecosystem health. These will be combined with future hydrological, climate, and socio-economic scenarios, informed by responses in our experiments and co-developed with project collaborators, the Environment Agency, to explore future threats to microbial freshwater ecosystems and wider ecosystem health.

The amount of plastic litter in in the environment is growing rapidly. Its presence poses a severe threat to marine and freshwater life. However, at the heart of our knowledge of plastic litter lies a black hole. The location of 99% or more of the plastic litter thought to be in the ocean is unknown. This makes it difficult to propose effective solutions for the problems associated with plastic litter. The main goal of this project is to predict what happens to different types of plastic litter in the environment. To achieve this, the degradation of commonly used plastics will be monitored under controlled laboratory conditions. Experimental methods to produce tiny fragments of plastics made from different polymers will be developed. These will be used to simulate their behaviour in the environment. For example, how quickly they fragment and sink under different conditions and how easily they transfer from water to river sediments. For comparison, plastics which are thought to degrade in a more environmentally-sustainable fashion will also be monitored. Results from these tests will be used to predict the fate of different types of plastics in the environment. They will also allow an assessment of the contribution that promoting sustainable types of plastics can make to solving the problem of plastic litter in the environment.

Groundwater turbidity above the drinking water limit is a common problem in groundwater supply boreholes that abstract from fractured aquifer systems, such as the Chalk in South East England. Strategies for managing such high turbidity events include blending or filtering the water or temporarily shutting down affected wells or borehole isolating borehole sections, which costs water companies and their customers several 10th of Millions of Pounds every year. While the source of turbidity can vary, the occurrence of turbidity spikes is usually associated with fast groundwater flows through fractures following prolonged rainfall or intensive storm events. The occurrence of such high turbidity events can currently not be predicted, posing a severe financial risk to water companies and limiting the reliability of the available groundwater resource. This project aims to develop an in-borehole monitoring system for continuously observing fracture inflows in boreholes and assessing their linkage to turbidity events. The system is based on Active Distributed Temperature Sensing (A-DTS) technology which uses fibre-optic cables installed in boreholes to continuously monitor the temperature changes within boreholes under ambient temperature conditions and in response to heat pulses, induced by heating a metal core within the cable. The project will therefore: 1. Demonstrate the suitability of A-DTS technology for quantifying in-situ fracture flow to groundwater boreholes. This will include testing different technological setups and monitoring strategies across a range of conditions and validating A-DTS technology against the results of traditional non-continuous borehole characterisation methods. 2. Develop a continuous A-DTS based early warning system of changes in fracture flow and turbidity. Therefore, in long-term (12 month) continuous monitoring of fracture flows additionally turbidity and electrical conductivity (EC) at different depths within the borehole will be monitored. 3. Identify Risk Zones for Borehole Turbidity by developing and applying numerical modelling tools to simulate groundwater (and suspended particles) flow through the subsurface under variable operational and meteorological conditions. This will allow the delineation of the most likely water and particle pathways and the mapping of risk zones that are most likely to deliver particles, and hence turbidity, to the investigated boreholes. The outputs of this study will directly benefit water companies by providing novel tools for identifying and characterising turbidity risk zones within and around existing supply borehole infrastructure. This will inform the design and implementation of risk amelioration measures and will also influence decision on locations, design and operation of new groundwater supply boreholes. The continuous A-DTS monitoring system will provide early warning of imminent turbidity events, providing water companies with an opportunity to adjust operation of their infrastructure prior to the event and thereby reducing the overall impact on their operational and supply infrastructure, hence saving costs for the operators as well as their customers. Modelling tools developed in this project will support the delineation of risk zones for groundwater contamination and thus, not only impact on the management of water resource infrastructure but also on surface infrastructure design, management and operations. Furthermore, the technology also has potential applications in the assessment of salinisation risks (e.g. by identifying and delineating risk zones within and around supply boreholes) as well as for detecting possible impacts of hydraulic fracturing operations on the groundwater flow regime (e.g. through identification of flow regime changes/ new fractures within existing boreholes). Keywords: turbidity, risk, groundwater supply, A-DTS, monitoring, early warning system, water industry, customers, fractured aquifers