Fire and water: predicting and mitigating water pollution risk from wildfire ash

Every year vegetation fires (wildfires and management burns) affect ~4% of the global vegetated land surface. This includes forests, grasslands or peatlands, which provide 60% of the water supply for the world's largest 100 cities and for 70% of for the UK's population. In England 114 km2 of uplands are affected by management burns alone and the UK Fire and Rescue Services attend to over 70,000 vegetation fires per year. Vegetation fires can have serious impacts on water quality, which, combined with the current and projected future further decline in fresh water availability and increase in fire risk in many regions around the world, has given rise to increased attention to water contamination risks from fire. The primary threat is ash left behind by fire, which can be transported very easily into water bodies by water erosion. Ash is typically rich in contaminants and its transfer into water supply catchments has led to numerous drinking-water restrictions and substantial treatments costs in recent years (e.g. for Belfast, Canberra, Denver, Fort McMurray, Sydney). In the UK, losses to the water industry from vegetation fires are estimated at £16 Mill. per year.

Models are widely used by scientists and land managers to predict soil erosion or flood risks after disturbance events such as harvesting or wildfire, however, no models currently exist that allow predicting of ash transport and associated water contamination risk following fire. This gap in knowledge and resource seriously compromises the ability of land managers to anticipate water contamination risks from fire and to implement effective mitigation treatments to reduce fire risk, prevent erosion after fire and, adjust water treatment capabilities.

This timely project brings together an interdisciplinary team of international experts from the UK, USA and Australia with the aim to address this critical knowledge and tools gap. Building on recent advances and proof-of-concept work in this field, we are now able to (i) obtain critical fundamental knowledge on wildfire ash transport processes and its contamination potential and, using this knowledge, to (b) develop the first end-user probabilistic model that allows predicting ash delivery and associated water contamination risk to the hydrological network.

The model will be validated for key fire-prone and fire-managed land cover types that have suffered critical ash-induced water pollution events in the past (including UK uplands, US conifer forest and Australian eucalyptus forest) using the first field dataset on ash transport parameters by water erosion and an extensive dataset on potential contamination by ash obtained through this project for these key regions.

To maximize the impact of the project, the web-based model will developed in collaboration with, and be made available to, users from land and catchment management sectors to support effective protection of aquatic ecosystems and drinking water supply from contamination by ash.

The ability to predict the risk of water contamination is essential in supporting environmental protection, to prevent or mitigate pollution events and to reduce risks of drinking water restrictions and water treatments costs. Given that ash from wildfire can pose a serious threat to water quality and that fire-affected regions provide 60% of the water supply for the world's largest 100 cities and to 70% for the UK's population, the tool developed here will have a major impact on the risk management of water supply catchments. Existing tools to predict the risk of soil erosion, landslides and flooding following disturbance events such as ERMiT are already widely used in the land management sector. The project will therefore fill an obvious and important gap.

It combines fundamental and applied research, and will maximise its impact by involving end-users from the outset and by including effective pathways for delivering outcomes to the wider academic and management end-user community.

Scientific and Academic beneficiaries: The outcomes will include the first comprehensive datasets on ash transport parameters and contaminant concentrations for key land cover types and will be freely available via the Environmental Information Data Centre. Both datasets will provide critical information to researchers in hydrology, hydrogeology, and water quality to enable predictions of ash induced contamination risks. Whilst not a focus of this project, the data obtained will also be relevant to air- and groundwater quality researchers. We will disseminate the scientific results and links to the datasets via international conferences and gold open access publications in high-impact journals.

Industry and Policy Makers: The model will provide a critical tool quantifying potential ash delivery and contamination risk to managers in the design of effective mitigation plans to prevent fire-induced water and air contamination, one of the present risks identified by DEFRA in its UK Climate Change Risk Assessment (UK-CCRA) 2017. This model will also enable to generate simulations for current and anticipated future climate and land management scenarios that are valuable in informing policies regarding land management and in promoting more effective fuel control measures using management burns as suggested in the UK-CCRA 2017.

To maximize these impacts, we will include two-way information exchange from the very outset with our national and international partners and their collaborators from the catchment management sector (Welsh Water, Brecon Beacons National Park, Melbourne Water and the US Forest Service). An open-access on-line version of the model will be designed specifically for end-users. To fully achieve the transfer of knowledge to end-users we will carry out two face-to face workshops and webinars to provide training to managers from our PPs and other potential users.

Public engagement: The education and involvement of the wider society is critical to achieve the goal of reducing fire-induced risks. To that end, we will incorporate a simplified version of the model into the web-interactive activity "Fire and Water" for primary and secondary school children to showcase the importance of fire for the functioning of ecosystems, the usefulness of fire and thinning operations to control fuel loads and prevent extreme fire events, and the potential impacts of wildfires or prescribed burns in poorly managed forests or heathlands on water quality. This activity will be included in the ongoing educational programme of our PP Welsh Water and showcased regionally at the National Waterfront Museum and the National Museum Cardiff programmes, the science communication project Oriel Science, and the Swansea Science Festival to showcase the societal benefits of research and to inspire, and receive feedback from, the general public. As in our previous work, we will also take advantage of wider dissemination opportunities via the media.