Grantee Research Project Results
Final Report: Fuel Reduction Techniques as Effective Forested Watershed Management Practices against Wildfire: Drinking Water Quality Aspects
EPA Grant Number: R835864Title: Fuel Reduction Techniques as Effective Forested Watershed Management Practices against Wildfire: Drinking Water Quality Aspects
Investigators: Karanfil, Tanju , Chow, Alex
Institution: Clemson University
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 2015 through August 31, 2018 (Extended to August 31, 2019)
Project Amount: $1,260,408
RFA: National Priorities: Systems-Based Strategies to Improve The Nation’s Ability to Plan And Respond to Water Scarcity and Drought Due to Climate Change (2014) RFA Text | Recipients Lists
Research Category: Water
Objective:
Detritus material in forest watersheds is the major terrestrial source of dissolved organic matter (DOM) and nutrients in source waters, but it is also the fuel igniting a forest fire. Fuel reduction techniques, including prescribed burning and mechanical thinning, could remove forest foliar litter, and thus, the risk of wildfire. Accordingly, periodic fuel reduction practices can reduce the accumulation of detritus material on the forest floor and the amounts of DOM exports after treatments. This 4-year, field-based research project investigated the consequences of different fuel reduction techniques, typically applied as watershed management practices against wildfire, for the export of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and inorganic nutrients from forested watersheds as well as the impact of these practices on associated biogeochemical processes and drinking water supplies. Specifically, the temporal variations of DOM exported from forested watersheds under prescribed burn or mechanical thinning were examined and compared with those from unmanaged watersheds to identify differences in the formation of regulated and emerging carbonaceous and nitrogenous disinfection byproducts (DBPs). The overarching goal of this project was to identify the best forest management practices to protect our source waters due to climate change. There were three specific objectives in this project:
Objective 1: Forest Management - Evaluate different fuel reduction techniques on the production and characteristics of DOC, DON, and inorganic nutrients
Objective 2: Watershed Processes - Quantify temporal variations and biogeochemical processes on DOC, DON, and nutrients exported from managed and unmanaged forested watersheds
Objective 3: Water Quality - Evaluate the efficacies of conventional water treatment processes on DOM removal and DBP formation from managed forested watersheds
Summary/Accomplishments (Outputs/Outcomes):
Our research team conducted a 4-year research study, including field-plot treatments, watershed- scale experiments, and instrument analyses to address the three objectives of forest management, watershed processes, and water quality, respectively. The field-plot treatments, including prescribed fire and mechanical thinning, were conducted at the Yawkey Wildlife Center and Clemson Experimental Forest, South Carolina. Litter was collected from managed and control plots for one-yield field incubation experiments. The watershed-scale burn was performed at the Santee Experimental Forest in Francis Marion National Forest, South Carolina. Intensive water samples from the paired watersheds were collected for over a year. In addition to general water quality parameters and the concentrations of nutrients, selected samples were analyzed for detailed molecular analysis using Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR- MS) and nuclear magnetic resonance spectroscopy (NMR) by Dr. Sarah Burton and Dr. Rosalie Chu at the Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory. In collaboration with Professor Randy Dahlgren at UC Davis and Professor Robert Rhew at UC Berkeley, we conducted a few other research studies (see Other Research Activities) to examine runoffs from wildfire and prescribed fires in California.
Objective 1, Forest Management, focused on identifying the best fuel reduction practices with respect to water quality and drinking water safety. First, we compared two fuel reduction techniques: prescribed fire and mechanical thinning. Experimental plots at Clemson Experimental Forest were manually thinned or burned in the same season. Surface detrital materials from the plots were collected and sorted into pre-burn vegetation, post-burned residuals, thinned-foliar litter, and thinned-woody residuals. Second, we evaluated the frequency and season of prescribed fire. These management practices were implemented in experimental field plots at the Tom Yawkey Wildlife Center in Georgetown, South Carolina. Surface detrital materials were collected from experimental plots including annual dormant season burn (i.e., burn every winter), annual growing season burn (i.e., burn every spring or summer), periodic growing season burn (i.e., burn every other 2 to 4 years in spring or summer), and non-burn control (> 25 years). All these materials were exposed in the natural field conditions over a year. Water leaching from these materials were examined for water treatability and DBP formation potential. The results of our experiments illustrated that residual biomass, especially foliar litter, from mechanical thinning could deteriorate source water by increasing DOC and nutrient loads. The increases of DOC concentration will increase the amount of coagulants and DBP formation during chlorination. For the sake of source water quality control, prescribed fire is preferred over mechanical thinning. Regarding the burning frequency and season, we did not observe significant differences in water quality among the three treatments (annual dormant, annual growing, and periodic growing season burns), in terms of alum and ferric removal efficiency and reactivity in DBP formation during chlorination and chloramination. On the other hand, the DOC exports from these three treatments were significantly lower than that of the non-burn control. Results demonstrated that prescribed fire could reduce DOC in source water and that the burning season and frequency did not impact source water. Therefore, landowners or foresters can manage their lands according to other needs, such as vegetation or beetle control.
Objective 2, Watershed Processes, focused on the temporal variation of water quality after long- term prescribed fire practices at the watershed scale. With support from the US Forest Service, a 155-ha area of the first-order watershed in the Santee Experimental Watershed was burned using aerial ignition in April 2016. Water exported from this watershed and an adjunct control watershed was closely monitored through three different water sampling techniques, including bi-weekly grab sample, flow-proportion auto-sampler, and in-situ DOC sensors. In addition to chemical parameters, we also evaluated water quality using biological indicators. Stream benthic macroinvertebrate samples were collected biweekly to determine if prescribed fire practices produced significant impacts on the aquatic biota, thus indicating changes in water quality. Results of these watershed-scale studies illustrated that DOC and DTN concentrations, as well as SUVA254, were significantly higher in the unmanaged watershed than in the managed watershed for most of the year (P < 0.05) and were linked to detrital thickness, precipitation, and flow patterns. The formation potential of DBPs, THMs, and HANs were higher in the unmanaged watershed for most of the sampling period (P < 0.05). In addition, both watersheds shared similar macroinvertebrate species richness, abundance, and diversity when we combined the data from the whole sampling year, although we often observed temporal differences in community between the two watersheds. Our study documented for the first time an improvement in source water quality and water treatability through long-term prescribed fire at the watershed scale.
Objective 3, Water Quality, focused on evaluating the efficacies of conventional treatments on DOC removal efficiency, DBP formation, and algal control. Samples included runoffs after the 2016 prescribed fire at the Santee Experimental Forest, South Carolina, and water samples with algae and Cu-based algicide from controlled laboratory experiments. In addition to DOC removal efficiency using alum and ferric coagulants and DBPs formation from both chlorination and chloramination, samples were characterized using FT-ICR-MS at the Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory. We did not observe any differences in the yield of DOC informing THMs when comparing prescribed fire and the corresponding reference sites. The burned watershed had a higher DON/DTN ratio compared to that of the unburned watershed, and its chemical fingerprint included smaller features (m/z < 750) and higher diversity of aliphatic and highly-unsaturated, oxygen-rich features. Slightly higher yields (reactivity) of HAAs during chlorination and NDMA from chloramination were observed from burned watersheds, but the overall DBP formation was still lower due to lower DOC concentrations (i.e., precursors) in the water. In fact, the increases of yield (reactivity) were observed only in the first few postfire runoffs. No obvious differences among treatments were observed in subsequent rain events. Overall, the molecular analyses showed that prescribed fire could alter the molecular size distribution, composition, and reactivity of DOM, but most of these notable changes occurred immediately after fire. Also, controlled laboratory study showed copper can effectively inhibit algal blooming, but it could serve as a catalyst to enhance DBP formation during chlorination.
Conclusions:
In sum, our study documented for the first time an improvement in source water quality and water treatability through long-term prescribed fire at the watershed scale. We also demonstrated that there were no differences in frequency (1–3 years) or season of prescribed fire on water quality, implying that landowners or foresters can manage their lands according to other needs, such as vegetation or beetle control. Although both mechanical thinning and prescribed fire can reduce fuel loads in forest ecosystems, prescribed fire is preferred over mechanical thinning because mechanical thinning can deteriorate source water by increasing DOC and nutrient concentrations. The results obtained to date indicate that systematic prescribed fire management can be used to reduce the fuel accumulation on the forested watershed floors and improve water treatability of the associated source water. Box models are created to summarize the effect of prescribed fire on the fuel loads in forest floor, and treatability and DBP formation in associated source waters.
Journal Articles on this Report : 10 Displayed | Download in RIS Format
Other project views: | All 39 publications | 10 publications in selected types | All 10 journal articles |
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Chen H, Uzun H, Chow AT, Karan T. Low water treatability efficiency of wildfire-induced dissolved organic matter and disinfection by-product precursors. Water Research 2020;184. |
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Chen H, Tsai K-P, Liu Y, Tolic N, Burton SD, Chu R, et al. Characterization of Dissolved Organic Matter from Wildfire-induced Microcystis aeruginosa Blooms controlled by Copper Sulfate as Disinfection Byproduct Precursors Using APPI(-) and ESI(-) FT-ICR MS. Water Research 2021;189. |
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Majidzadeh H, Chen H, Coates TA, Tsai KP, Olivares CI, Trettin C, Uzun H, Karanfil T, Chow AT. Long-term watershed management is an effective strategy to reduce organic matter export and disinfection by-product precursors in source water. International Journal of Wildland Fire 2019;28(10):804-813. |
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Olivares C, Uzun H, Cagri E, Zhang WB, Trettin C, Liu Y, Burton S, Robinson E, Karanfil T, and Chow AT (2021) Increased organohalogen diversity after disinfection of water from a prescribed burn watershed. ACS ES&T Water 1(5):1274-1282. |
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Tsai K, Uzun H, Karanfil T, Chow, A. Dynamic Changes of Disinfection Byproduct Precursors following Exposures of Microcystis aeruginosa to Wildfire Ash Solutions. Environ. Sci. Technol., 2017, 51, pp 8272–8282. |
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Uzun H, Zhang W, Olivares CI, Erdem CU, Coates TA, Karanfil T, et al. Effect of prescribed fires on the export of dissolved organic matter, precursors of disinfection by-products, and water treatability. Water Research 2020;187. |
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Uzun H, Dahlgren RA, Olivares C, Erdem CU, Karanfil T, Chow AT. Two years of post-wildfire impacts on dissolved organic matter, nitrogen, and precursors of disinfection by-products in California stream waters. Water Research 2020;181. |
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Ruecker A, Uzun H, Karanfil T, Tsui MTK., Chow, A. Disinfection Byproduct Precursor Dynamics and Water Treatability during an Extreme Flooding Event in a Coastal Blackwater River in Southeastern United States. Chemosphere 2017, 188, 90–98. |
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Tsai KP, Uzun H, Chen H, Karanfil T, Chow AT. Control wildfire-induced Microcystis aeruginosa blooms by copper sulfate:trade-offs between reducing algal organic matter and promoting disinfection byproduct formation. Water research 2019;158:227-236. |
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Olivares CI, Zhang W, Uzun H, Erdem CU, Majidzadeh H, Trettin C, Karanfil T, Chow A. Optical in-situ sensors capture dissolved organic carbon (DOC) dynamics after prescribed fire in high-DOC forest watersheds. International Journal of Wildland Fire 2019;28(10):761-768. |
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Supplemental Keywords:
Disinfection Byproducts, Wildland FireProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.