Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for “source water supply and protection” strategies

Elevated suspended solids, including initial pulses of ash from storms following wildfire, can impact water treatment, threatening attainment of drinking water standards for turbidity and increasing filtration and coagulation costs.

“Elevated suspended solids, including initial pulses of ash from storms following wildfire, can impact water treatment, threatening attainment of drinking water standards for turbidity and increasing filtration and coagulation costs (Emelko et al., 2011; Murphy et al., 2015).”

From a water supply perspective, postfire sediment loads increase the probability of degrading water quality (taste, odor, color), impairing drinking-water treatment processes and decreasing the operational life-span of reservoirs.

“From a water supply perspective, postfire sediment loads increase the probability of degrading water quality (taste, odor, color), impairing drinking-water treatment processes and decreasing the operational life-span of reservoirs.13”

Postfire sediment loads and turbidity are generally much higher and more variable than in undisturbed streams, especially following severe fires and after storm flows or during spring snowmelt.

“Postfire sediment loads and turbidity are generally much higher and more variable than in undisturbed streams, especially following severe fires and after storm flows or during spring snowmelt.9,13”

In the first four years after the Lost Creek wildfire in Alberta, the 95th percentile dissolved organic carbon remained low in streams draining unburned watersheds (3.8 mg L−1), while dissolved organic carbon levels were elevated in streams draining burned (4.6 mg L−1) and postfire salvage-logged (9.9 mg L−1) watersheds.

“Similarly, in the first four years after the Lost Creek wildfire in Alberta the 95th percentile DOC remained low in streams draining unburned watersheds (3.8 mg L -1 ).In contrast, DOC levels were elevated in streams draining burned (4.6 mg L -1 ) and postfire salvage-logged (9.9 mg L -1 ) watersheds. 13”

Excess dissolved organic carbon is a concern for downstream community water supply and consumer health because it can create taste and odor problems, decrease water treatment effectiveness, increase formation of potentially carcinogenic disinfection byproducts, and increase operating costs in impacted communities.

“Excess DOC is also a concern for downstream community water supply and consumer health because it can create taste and odor problems, decrease the effectiveness of the water treatment process, increase the formation of potentially carcinogenic chemical disinfection byproducts, and ultimately increase operating costs in impacted communities.13,75”

An extremely high mercury pulse of 265 μg L-1 was measured after a moderate precipitation event (approximately 20 mm) several days following a very large event that fully saturated the ground and produced very high stormflow.

“An extremely high mercury pulse of 265 μg L -1 (0.001 μg L -1 = maximum acceptable concentration in drinking water) was measured after a moderate precipitation event (∼20 mm) several days following a very large event that fully saturated the ground and produced very high stormflow.13”

Streams that drain burned forested landscapes often have increased levels of phosphorus, nitrogen, dissolved organic carbon (DOC), sulfate, chloride, calcium, magnesium, sodium, and potassium.

“Streams that drain burned forested landscapes often have increased levels of phosphorus, nitrogen, dissolved organic carbon (DOC), sulfate, chloride, calcium, magnesium, sodium, and potassium.5,13”

Increases in organic carbon have been observed in temperate and boreal regions.

“Increases in organic carbon have been observed in temperate (Emelko et al., 2011; Murphy et al., 2018; Writer et al., 2014) and boreal regions (Allen et al., 2003, 2005; Crilly et al., 2017).”

Research has only recently focused on linkages between on-site and downstream impacts of fire on water quality and on treatability of contaminated water following fire.

“research has only recently focused on linkages between on-site and downstream impacts of fire on water quality (Abraham, Dowling, & Florentine, 2017;Bladon, Emelko, Silins, & Stone, 2014;Smith, Sheridan, Lane, Nyman, & Haydon, 2011) and treatability of contaminated water following fire (Emelko, Silins, Bladon, & Stone, 2011).”

The body of research on post-fire water contamination is still relatively small with enormous variability in reported drivers of post-fire contamination events and location- or end user-specific questions.

“the body of research is still relatively small with enormous variability in the reported drivers of post-fire contamination events (type of pollutants and mobilization processes; Moody et al., 2013) and location-or end user-specific questions (e.g., White et al., 2006;Emelko et al., 2011;Campos et al., 2012;Santín, Doerr, Otero, & Chafer, 2015;Santos, Sanches Fernandes, Pereira, Cortes, & Pacheco,”

Heavy metals may pose significant threats to ecosystem health, but they can be effectively removed by most conventional and advanced drinking water treatment processes.

“For example, while heavy metals may pose significant threats to ecosystem health, they can be effectively removed by most conventional and advanced drinking water treatment processes (see Emelko et al., 2011 for links of contaminants of concern to drinking water infrastructure typologies).”

Rapid identification of water contamination and treatment risks after the Fort McMurray fire was informed by previous long-term, post-fire, catchment-scale hydrological research conducted in different hydrologic, geologic, and physiographic settings of Alberta's south-eastern, steep-sloped Rocky Mountains.

“While operational expertise and wise infrastructure investment largely enabled this success, rapid identification of water contamination and treatment risks was informed by previous long-term, post-fire, catchment-scale hydrological research (Emelko et al., 2011(Emelko et al., , 2016;;Silins et al., 2009) that was conducted in the different hydrologic, geologic, and physiographic settings of”

Global-scale studies or assessments of wildfire effects or risks on water resources are lacking.

“Although a significant number of studies have examined such second-order fire effects on surface freshwater resources [8], most have been conducted at a local or regional scale [8-12], whereas global-scale studies do not exist.”