Field-scale methodology for the assessment of water-based wildfire suppression efficiency

Critical water volumes needed for wildfire containment are currently estimated using theoretical energy balance models. The actual suppression efficiency of water-based systems remains largely unvalidated at operationally relevant fireline intensities, as prior critical water volume studies have been restricted to low-intensity experimental fires (typically \((< 1000 \text{ kW/m})\)). To scale the empirical assessment to operationally relevant fireline intensities, a reliable and repeatable methodology, together with a custom apparatus, has been developed. The proposed protocol utilizes a custom soaker hose system, characterized for its wetting pattern under wind, to create pre-wetted strips of vegetation in the path of advancing fires in experimental and prescribed burn scenarios. The soaker hose system enabled the empirical quantification of water deposition depths \((\text{(d}_\text{w}; mm))\) and verifiable containment outcomes. Ten fire tests were conducted in Portugal and Spain, delivering applied \((\text{d}_\text{w})\) between \((0.9 \text{ mm})\) and \((3.1 \text{ mm})\), exposed to advancing fire fronts with fireline intensities ranging from roughly \((2500 \text{ kW/m})\) up to \((5500 \text{ kW/m})\). Field data presented in this work successfully narrow the large theoretical operating window of this bespoke soaker hose. This methodology provides a repeatable framework for the field-based study of the suppression efficiency of water-carrying appliances at relevant fireline intensities.