Effects of Wildfires and Fuel Treatment Strategies on Watershed Water Quantity across the Contiguous United States JFSP PROJECT ID: 14 1 06 18

Water supplies in the United States are experiencing stress from more frequent and severe droughts accompanied by extreme wildfires (Dennison and others 2014). These fires consume forest canopies and can cause extensive property damage. Severe wildfires produce a cascade of indirect hazards triggered by rainstorms, such as floods, excessive erosion, and debris flows (Cannon and others 2011, Elliott and Parker 2001, Littell and others 2016, Moody and others 2001, Neary and others 2005, Shakesby and Doerr 2006, Williams and others 2014). Large and severe fires also affect the amount and quality of water supplied by rivers, sometimes over the course of years (Hallema and others 2018a, Rhoades and others 2018). Consequently, fires not only affect the people living near forests (Radeloff and others 2018), but also those living outside the immediate range of these fires.Post-fire threats cause uncertainty about the amount and quality of surface water, and increase the cost of water treatment and flood mitigation (Bladon and others 2014, Martin 2016). The effect of any particular fire on surface water is often difficult to detect over a longer time frame given due to a variety of confounding factors. Some of these factors pertain to the inter-annual variability in climate and evapotranspiration (Hallema and others 2017a), and others are related to the complexity of landscape interactions and the time it takes for water to move through the basin (Hallema and others 2017b). Fire effects on surface water further depend on the extent and severity of a fire (Hallema and others 2018a).