Qualitative risk analysis of invasive pathogens spreading via raw water transfers in the UK

Raw water transfers (RWT) are artificial movements of untreated water, often constructed from areas of high supply and low demand to areas of low supply and high demand for potable water, industry and irrigation, but also to meet environmental requirements, such as to maintain river flow. Increasing demands on water infrastructure coupled with climate change mean that the reliance of the water industry on RWT will increase significantly within the next decade. RWTs are recognised as a high-risk pathway for the spread of freshwater invasive non-native species (INNS), however the movement of invasive micro-organisms via RWT is yet to be explored. This study aims to qualitatively assess the risk of transfer and establishment of invasive pathogens as a result of RWTs. Using the Source-Pathway-Receptor-Consequence model, the pathways and processes involved in micro-organism movement due to RWT are mapped, and high and low risk scenarios with respect to pathogen spread via RWT are presented. The biological factors affecting the survival and persistence of pathogens are discussed, and how these interact with the physical parameters of RWT. We have highlighted potential freshwater diseases of importance to the UK and demonstrated their potential for transmission via RWT due to their to persistence within the environment. This risk analysis provides evidence that a more detailed study of pathogen interactions with RWT variables is required to enable quantitative risk assessments to be made, in anticipation of future legislative policy.