TAMING THE WILD – UNDERSTANDING RISKS AND RESPONSES TO WATER SUPPLIES FROM WILDFIRES Glen Leverich 1 Rodrigo Prugue 2 2 0 19 P N WS - AWWA Conference, Vancouver, WA May 3, 2019 1 2 OUTLINE OF TALK Photo of City of Brookings, OR (courtesy of City of Brookings) OVERVIEW OF WILDFIRE ACTIVITY AND RISKS IN THE NORTHWEST Photo of Chetco Bar Fire (courtesy of USFS) Spatial frequency of recorded burn events in OR and WA: 1908–2017 Annual total acres burned in OR and WA: 1908–2018 Vancouver Chetco R. Source data: BLM, 2017 Source data: BLM, 2018 GIS analysis: Stillwater, 2018 Analysis: Stillwater, 2019 Conceptualization of sediment yield and associated vegetation and litter recovery • Wildfires can lead to during the fire-induced “window of accelerated rates of runoff disturbance” and erosion Increasing vegetation cover • Exposed, burned soils influence of erosion-limiting during storms are more factors litter cover susceptible to mass wasting and sediment- fire-induced sediment laden runoff—the Fire- yield Flood-Erosion sequence ‘background’ (Neary et al., 2005, USDA) E R I F sediment yield • “Window of disturbance” S E D I M E N T Y I E L D occurs for months to years window of disturbance until natural system T I M E recovers (Prosser and Adapted from Shakesby and Doerr, 2006, Williams, 1998, Hyd. Proc.) Earth Sci. Rev. Photo of burned area of Chetco watershed (Stillwater Sciences) Photo of Montecito Debris flows following Thomas Fire in Santa Barbara County, CA, Jan 2018 (photo courtesy of Scripps Institute) WILDFIRE EFFECTS TO DRINKING WATER SUPPLY Photo of burned area of Chetco watershed (Stillwater Sciences) WILDFIRE EFFECTS TO DRINKING WATER SUPPLY •Two-thirds of freshwater resources in the U.S. originate on forested land (National Research Council) •Three-quarters of OR and WA residents receive drinking water from 2,700 (OR) and Vancouver 17,000 (WA) water systems (ODEQ, WDOH) •Are facilities prepared for increases in wildfire activity? •Early warning systems? •Ability to shutdown intake? Surface-water and groundwater •Alternate sources? Chetco R. source protection areas in relation to wildfire activity CASE STUDY: CITY OF BROOKINGS MUNICIPAL WATERSHED POST-FIRE ASSESSMENT • Address potential effects on City’s water system following the major Chetco Bar Fire in 2017 • Has water quality changed? • Have geomorphic changes occurred that could undermine the water-intake structure? • Do the post-fire changes pose a risk to the City’s water supply? • Hydrology-Geomorphology and Water Quality Assessments • Assess water quality in the City’s source water and potential treatment issues • Assess flow and channel conditions and potential scour and/or aggradation impacts to the infiltration gallery • Develop a “Wildfire Source Water Protection Sampling and Analysis Plan” Photo courtesy of Del Norte Triplicate News Study location: • CityFrequent of Brookings, wildfires pop.and increasing6,550 • Chetcoair temps River in recent watershed: years 350 mi2 • HighWildfires quality have water occurred during • Riverbankabove-normal filtration and below intake-normal • Avgwater production=1.2 years MGD • PumpedMajor storm to treatment and flood plantevents • Package(>5 yr RI) planthave systemnot occurred within 3 years of any of the major wildfires Ranney Collector HYDROLOGY & GEOMORPHOLOGY ASSESSMENT • Assess post-fire changes to runoff hydrology and channel morphology at infiltration gallery Ranney Collector • Understand effects from past wildfires (Biscuit Complex) • Utilize USFS BAER information and interviews • Field reconnaissance • Establish photo-log monitoring locations to identify changes in channelGeomorphically morphologyactive lowchannel-cost locationand repeatable by City staff Confluence of mainstem and NF river 3/30/201920162013201220112005200420031994 Planet Labs satellite 4m imagery CHANGES IN RUNOFF VS. RAINFALL? Annual Total Runoff of Chetco River versus Annual Total Precipitation in Brookings during WY 1970–mid-2019 All Water Years (1970-2019) 3,200,000 Water Years within 3 Years after Silver Fire (WY 1988-1990) Water Years within 3 Years after Biscuit Complex Fire (WY 2003-2005) Water Years within 2 Years after Chetco Bar Fire (WY 2018-2019) 2,700,000 y = 25692x - 334986 R² = 0.7659 feet) - 2,200,000 1,700,000 1,200,000 Annual Total Runoff (acre Runoff Total Annual 700,000 200,000 40 50 60 70 80 90 100 110 120 130 Annual Total Precipitation (in) • No clustering of post-fire data in the 50-year record • Rainfall-runoff relationship, at the USGS gage, exhibited no unusual pattern during those fire-recovery years CHANGES IN RUNOFF FLASHINESS? Runoff Ratio for Chetco River R-B Index (Flashiness) for Runoff in Chetco River 2.5 0.45 Silver Biscuit Complex Chetco Bar Silver Biscuit Complex Chetco Bar 퐴푛푛푢푎푙 푅푢푛표푓푓 퐷푒푝푡ℎ 0.4 2 퐴푛푛푢푎푙 푅푎푛푓푎푙푙 퐷푒푝푡ℎ 0.35 y = 0.0002x - 0.0902 R² = 0.0052 y = -0.005x + 11.423 0.3 R² = 0.0723 1.5 0.25 0.2 1 Richards-Baker flashiness index 0.15 (Baker et al. 2004) B Index (dimensionless flashiness) runoff for metric (dimensionless BIndex Full Record (WY 1970-mid-2019) - Full Record (WY 1970-mid-2019) 0.1 0.5 Prior to 1987 Silver Fire (WY 1970-1987) Prior to 1987 Silver Fire (WY 1970-1987) Between 1987 Silver Fire and 2002 Biscuit Fire (WY 1987-2002) Annual R Annual AnnualRORatio (dimensionless metric runofffor change) Between 1987 Silver Fire and Biscuit Fire (WY 1987-2002) 0.05 Between 2002 Biscuit Complex Fire and 2017 Chetco Bar Fire (WY 2002-2017) Between 2002 Biscuit Complex Fire and 2017 Chetco Bar Fire (WY 2002-2017) After 2017 Chetco Bar Fire (WY 2017-mid-2019) After 2017 Chetco Bar Fire (2018-2019) 0 0 1970 1980 1990 2000 2010 2020 1970 1980 1990 2000 2010 2020 Water Year (1970–mid-2019) Water Year (1970–mid-2019) • No consistent increase (or decrease) following fire events • Thus, none of the events led to a measurable change in runoff or flashiness as observed at the USGS gage USFS BURNED AREA EMERGENCY RESPONSE (BAER) FORECASTS •Post-fire sediment-delivery rates for the 2-yr and 5-yr storm events were estimated to be a factor of 10–100 greater than pre-fire rates from the burned areas (USFS 2017, Chetco Bar Fire BAER Report) •Similar forecasts were made following the Silver and Biscuit fires, but were not realized due to mild storm activity following those events •The importance of the sediment- delivery rates is in their predicted relative sediment-delivery potential from each of the watershed’s major tributaries HYDRO-GEOMORPHOLOGY FIELDWORK •Conducted soon after largest storm of year •Established long-term photo- monitoring points •Minimal post-fire material deposited near Ranney Collector •Turbid waters only observed in burned portions of upper watershed with active salvage logging WATER QUALITY ASSESSMENT • Assessment Goal: Understand water quality impacts as a result of Chetco Fire. • Delineate Chetco River from North Fork Chetco River • Overarching Goal: Determine potential near-/long-term impacts of Chetco Bar Fire. FIELD METHODS • Two post-fire sampling events • Parameters conducted. • General • January 30, 2018 • Major Anions/Cations • Nutrients (relatively dry conditions) • Metals • March 23, 2018 (relatively • Microbial wet conditions) General Conditions During Sampling Events Event 1 (Dry) Event 2 (Wet) Condition January 30, 2018 March 23, 2018 Mean temperature* (°F) 41 to 54 °F 41 to 46 °F Total measured precipitation for the 0.24 inch 1.13 inches day* Peak flow measured at Chetco River (measured from gauge: 14400000) 5,460 cfs 9,420 cfs Notes: * Weather conditions based on data from Weather Underground (KBOK location near Brookings, Oregon). °F = degrees Fahrenheit cfs = cubic feet per second FIELD METHODS FIELD METHODS FIELD METHODS • … • … RESULTS – PRE-RAIN EVENT 35 Metals General Chemistry 30 25 20 15 Concentration (mg/L) Concentration 10 5 0 Total Iron Total Manganese* Total Sodium Sulfate Total Organic Carbon Total Suspended Solids Analyte DEQ 4/22/2013 Main Stem 1/30/2018 North Fork 1/31/2018 Ranney Collector 2/1/2018 RESULTS – AFTER RAIN EVENT 35 Metals General Chemistry 30 25 20 15 Concentration (mg/L) Concentration 10 5 0 Total Iron Total Manganese* Total Sodium Sulfate Total Organic Carbon Total Suspended Solids Analyte DEQ 4/22/2013 Main Stem 3/21/2018 North Fork 3/21/2018 Ranney Collector 3/21/2018 WATER QUALITY ASSESSMENT • Initial Findings • Results indicate no significant water quality impacts. • Impacts specific to dissolved organic carbon, iron, and aluminum. • Undetected in Ranney well collector. • However, difficult to make definitive conclusions from initial sampling events. • Recent water quality data appear to be similar to historical sampling event results. • Monitoring Plan developed for City as a result of case study CONCLUSIONS • Findings: • Generally, wildfires can impact water quality and treatment operations • Chetco watershed’s physical characteristics have buffered effects to water quality from wildfire… so far. • Potential for post-fire impacts to the Ranney Collector from scour of the river channel appears low… so far. • The increase in wildfire activity could potentially overwhelm the watershed’s resilience to wildfire impacts in the future. • Results indicate no significant water quality impacts to date. • Most parameters appear unaffected in surface water samples. • Products: • “Wildfire Source Water Protection Sampling and Analysis Plan” • Recommendations: • Continue low-cost monitoring of geomorphic and water quality changes early warning detection • Collaboration and information sharing with federal, state, tribal, city, and private groups • Explore additional water supplies Acknowledgements • City of Brookings • Oregon Business Development Department • Jacobs • GSI staff: Ronan Igloria • Stillwater staff: Dylan Caldwell, Karley Rodriguez, Derek Booth • Stantec staff: Pete Kreft, Andrew Nichihara • Technical support from US Forest Service (Joni Brazier), DEQ (Bryan Duggan), ODFW (T. Slaven).