Designing tools to predict and mitigate impacts on water quality following the Australian 2019/2020 wildfires: Insights from Sydney's largest water supply catchment

Abstract

EDITOR'S NOTE: This article is part of the special series "Ecological consequences of wildfires." The series documents the impacts of large-scale wildfires in many areas of the globe on biodiversity and ecosystem condition in both terrestrial and aquatic ecosystems, the capacity for systems to recover and management practices needed to prevent such destruction in the future.

Evaluating the Persistence of Post-Wildfire Ash: A Multi-Platform Spatiotemporal Analysis

“…In addition to ash cover and depth measurements, a composite ash sample was collected in a 400 cm 2 frame, which was oven-dried and weighed, and the ash bulk density was calculated in the lab for the three highest severity transects (Table 3). As emphasized in the introduction, the WATAR hydrologic model that is used to predict ash transport requires ash load (mass per area) as an input [24]. From the ash cover, depth, and weight data, we can calculate an ash load for each transect; similarly, we can also do this using the calculated bulk density.…”

“…Water quality degradation is likely if elevated runoff, soil erosion, or ash transport occurs after the wildfire [18,22,23]. Scientists have raised awareness regarding wildfire ash impacts on drinking water supplies particularly in areas that experience severe wildfires [24,25].…”

“…Post-fire ash transport models are being developed [24] and a principle motivation of this study is working towards a methodology for quantifying ash after wildfires for use in these models [29]. To predict the transport and fate of ash (or any pollutant), a model needs a spatially explicit estimate of the amount or load available for transport.…”

“…Optical remote sensing has shown promise for mapping ash cover [9,32,33] and even load [34], although these methods have not been widely implemented. A spatially explicit map of ash load is used as an input into a hydrologic model, such as the Water Erosion Prediction Project cloud-Wildfire Ash Transport and Risk (WEPPcloud-WATAR) model, and together with topographic, soil, and climate data, it is used to predict the delivery of ash and the associated contaminants to water bodies [24]. These modelling exercises are practical and applied rather than theoretical and are widely used by land managers around the world to plan and mitigate post-wildfire hydrologic disasters.…”

Advances on water quality modeling in burned areas: A review

“…Within the post-fire context, empirical models such as the Universal Soil Loss Equation (USLE) and its revised version (RUSLE) have often been used for soil erosion predictions, while more complex models have been generally used to predict post-fire runoff and erosion [30][31][32], as well as the effects of post-fire erosion mitigation treatments at slope and catchment scale [32,33]. However, only a limited number of models have been used to predict the impacts of fires on water quality [34][35][36][37][38][39]. It should also be highlighted that only a few models were designed for post-fire conditions [26].…”