Grantee Research Project Results
Final Report: An Integrated Modeling and Decision Framework to Evaluate Adaptation Strategies for Sustainable Drinking Water utility management under drought and climate change
EPA Grant Number: R835865Title: An Integrated Modeling and Decision Framework to Evaluate Adaptation Strategies for Sustainable Drinking Water utility management under drought and climate change
Investigators: Ozekin, Kenan , Summers, R. Scott , Kasprzyk, Joseph Robert , Rajagopalan, Balaji , Rosario-Ortiz, Fernando , Livneh, Benjamin
Institution: Water Research Foundation , University of Colorado at Boulder
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 2015 through August 31, 2018 (Extended to August 31, 2019)
Project Amount: $1,250,000
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:
Drought due to climate change and other extreme events such as wildfire and floods challenge drinking water utilities’ ability to treat water to meet regulatory and public health protection goals, with turbidity and disinfection byproducts (DBPs) control as the critical water quality (WQ) issues. The objectives of the research are to: (1) understand the flow and sediment generation from water supply watersheds in response to scenarios of hydro-climatological extremes and natural hazards, (2) understand the mobilization and transport of organic matter and sediments, and in some cases nutrients, through the watershed and eventually to the water treatment plant (WTP), (3) develop source water thresholds for turbidity and DBP precursors based on finished water regulatory constraints and using stream WQ data with extreme value theory predict WQ threshold exceedances, and (4) evaluate a suite of adaptation and operation strategies (e.g., watershed management, wildfire mitigation, WTP modifications) along with their economic, societal and policy implications - with multi-objective optimization and multi-criteria analysis tools.
Summary/Accomplishments (Outputs/Outcomes):
Climate change and its manifestation in the hydrologic cycle and extreme events could have a profound impact on water quality, as well as water quantity. These impacts will be felt by drinking water systems - especially by utilities charged with the task of providing a safe and reliable supply of water to the public. The impact is felt through variability in a suite of water quality variables that are relevant to stream ecosystems and drinking water treatment. This is further exacerbated by natural hazards such as fire in the water supply watershed combining with climate extremes. For example, drought produces lower water supply but if it is punctuated by extreme wet events and fires they mobilize a lot of sediments (turbidity), nutrients and dissolved organic content (DOC) – all of which have a significant impact on water utilities in their mission to deliver safe and reliable drinking water. There are several studies investigating the impact of climate change on water quantity, however, there is a paucity of tools relating them to water quality. Such an understanding and set of tools would enable efficient planning and management strategies and also aid in setting more-sensible regulatory policies. With this main motivation, we proposed an interdisciplinary framework with four broad activities – (i) understanding watershed response to post-fire sedimentation, (ii) understanding the heating due to fires on mobilization of organic carbon, (iii) understanding water quality thresholds, exceedances and modeling using climate and land surface variables and, (iv) decision support tool to adapt to varying water quality. The outcomes of these activities are summarized below.
Activity 1: Estimating watershed-scale response of post-fire sediment
A generalized model of watershed-scale streamflow and suspended sediment was developed to simulate the impacts of climate and land cover disturbances on flow volumes and sediment transport. Five erosion and suspended sediment load algorithms were applied, showing larger year-to-year variation in suspended sediment than previous estimates. The simulated sediment is sensitive to climate conditions and so the model results provide new insights into how suspended sediment is likely to respond to changing climate conditions and extremes. The sensitivity of sediment response to wildfire was also evaluated within the model, showing a large and distinct increase in sediment loading after a wildfire. An exclusively data-driven analysis of post-fire streamflow was conducted over the western U.S. suggesting that post-fire signals are often masked by data limitations, underscoring the necessity of a well-validated model to predict post-fire sediment responses.
Towards the end of the project, a laboratory-scale rainfall simulator and burning apparatus was constructed to measure sediment responses across a range of terrain slopes, wildfire intensities, and rainfall intensities. The construction of this apparatus is an important outcome that allows for detailed measurements of slope, fire, and storm impacts on sediment transport. Preliminary analysis suggests that wildfire severity will be the largest driver of suspended sediment, with slope and rainfall intensity playing secondary roles.
Activity 2: Impact of Heating Temperature on the Character of Water-Soluble Constituents from Organic and Mineral Soils
Wildfires are a natural and ubiquitous phenomenon that often leave behind a perturbed environment. Post-fire landscapes become susceptible to enhanced erosion, decreased infiltration capacity, and soil hydrophobicity, which facilitate the transport of post-fire residue into surface waters that often serve as potable water sources. The risks posed by post-fire residue, or ash, deposition to raw water sources and subsequent impairment of water quality is difficult to understand due to the complex nature of wildfire effects. To address the impacts of ash on water quality, surface soils and litter were progressively heated to a range of temperatures (150 to 550˚C) and subsequently leached in water to evaluate changes in the release of dissolvable constituents as a function of burn temperature. Water quality parameters assessed include dissolved organic carbon (DOC), dissolved organic nitrogen (DON), dissolved inorganic nitrogen (DIN), fractions of water extractable organic carbon and nitrogen (WEOC and WEON), and soluble elements. Following heating, both the quantity and solubility of DOC and DON from soil were enhanced at 250˚C to 350˚C while that from litter decreased drastically after material was heated above 150˚C. DOC contributions from litter across all temperatures exceeded that from soil while DON contributions for both materials were comparable. Soluble elements ranged in trends; however, litter concentrations were magnitudes higher than soil in general for all except for Al and Mn, which were comparable between materials. This work contributes to the growing understanding of the impacts of wildfires on water quality in general and helps identify major contributors (soil or litter) to water quality risk based on fire severity.
Activity 3: Source Water Quality Thresholds and Exceedance Evaluation
Spatio-temporal variability of surface water quality impacts the regulatory compliance of the finished water from drinking water utilities, consequently, impacting public health. Of particular interest are the concentration of total organic carbon (TOC), turbidity and bromide. TOC reacts with common disinfectants, such as chlorine to form regulated and unregulated disinfection byproducts (DBPs). Bromide also increases the formation of DBPs and their health effects. Turbidity is an indicator of potential presence of pathogenic microorganisms. In many cases turbidity, TOC and bromide concentrations vary significantly seasonally and across the country. Thus, understanding and modeling the thresholds and the variability of these constituents in the influent waters of the treatment plant is crucial in developing mitigation strategies.
To this end, this activity of the project had two broad objectives – (i) Determine source water thresholds for TOC, bromide, and turbidity based on regulatory constraints in the finished water and use source water quality data with extreme value theory to model water quality threshold exceedances. (ii) Develop models that relate surface water quality concentrations to historic climate (precipitation, temperature, drought index) and land surface variables (vegetation index). We developed thresholds for TOC and bromide at representative sample locations with diverse climate. Statistical learning methods based on regression trees and nonlinear regression were used in the development of skillful models for TOC and turbidity using climate and land variables, bypassing, streamflow. This is a significant contribution in that, streamflow data is often hard to obtain, while climate and land surface variables are readily available. Extreme Value Theory was applied to model threshold exceedances of TOC, which will be of immense help in developing meaningful regulatory regime, to enable safe drinking water. A framework for demonstrating the probability of target level turbidities being exceeded given increases in prior process turbidity levels was developed and applied to utility data. These probabilities of target exceedances provide utilities with an opportunity to perform a risk based assessment of their utility operations. Relationships between source water turbidity levels to settled and filter effluent turbidities, and settled water turbidity levels to combined filter effluent (CFE), are uniquely described via the novel zoning methodology presented in this activity. Each zone provides insight to how signals of turbidity propagate throughout the treatment train.
Activity 4: Decision support tool for adapting to variable water quality and competing objectives
The fourth objective was to develop a decision support tool to help utilities adapt to changing source water conditions and improve the reliability and efficiency of treatment. To integrate the preferences of real water managers, researchers developed this tool based on input from water utilities from across the United States. Based on this feedback, researchers designed a simulation-optimization tool capable of generating innovative operating policies for existing treatment facilities. The benefit of this approach was illustrated via a disinfection byproduct (DBP) management case study in northern Colorado. In this case study, the tool generated a suite of chemical dosing strategies that improved the reliability and adaptability of treatment plant operations. Moreover, these results offered the utility with insights about the tradeoffs among competing treatment objectives, such as operational costs and risks of regulation violation.
The development of the decision support tool was made possible through innovations in stochastic water quality methods, water treatment simulation, multi-objective optimization, and interactive visualization techniques. In this project, researchers advanced stochastic water quality methods to generate realistic scenarios of source water quality and characterize water quality uncertainty. Regarding simulation and optimization, researchers coupled the USEPA Water Treatment Plant Model—developed to estimate DBP formation and DBP precursor removal—with a multi-objective evolutionary algorithm to discover safer and more efficient operational decisions. Lastly, researchers developed interactive visualization techniques to enhance data exploration, and ultimately, treatment decision making.
Journal Articles on this Report : 11 Displayed | Download in RIS Format
Other project views: | All 50 publications | 11 publications in selected types | All 11 journal articles |
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McKay G, Hohner AK, Rosario-Ortiz FL. Use of optical properties for evaluating the presence of pyrogenic organic matter in thermally altered soil leachates. Environmental Science-Processes & Impacts. 2020;22(4):981-92. |
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Raseman R, Kasprzyk J, Summers R, Hohner A, Orsario-Ortiz F. Multi-objective optimization of water treatment operations for disinfection byproduct control. Environmental Science:Water Research & Technology 2020;6:702-714. |
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Raseman WJ, Kasprzyk JR, Rosario-Ortiz FL, Stewart JR, Livneh B. Emerging investigators series: a critical review of decision support systems for water treatment: making the case for incorporating climate change and climate extremes. Environmental Science: Water Research & Technology. 2017;3(1):18-36. |
R835865 (2017) R835865 (Final) |
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Raseman WJ, Kasprzyk JR, Rosario-Ortiz FL, Stewart JR, Livneh B. Emerging investigators series: a critical review of decision support systems for water treatment: making the case for incorporating climate change and climate extremes. Environmental Science: Water Research and Technology 2017;3(1):18-36. |
R835865 (2016) R835865 (2017) R835865 (2018) R835865 (Final) |
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Raseman WJ, Jacobson J, Kasprzyk JR. Parasol:an open source, interactive parallel coordinates library for multi-objective decision making. Environmental Modelling & Software. 2019;116:153-63. |
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Samson CC, Rajagopalan B, Summers RS. Modeling source water TOC using hydroclimate variables and local polynomial regression. Environmental Science & Technology 2016;50(8):4413-4421. |
R835865 (2016) R835865 (2017) R835865 (2018) R835865 (Final) |
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Samson CC, Rajagopalan B, Summers RS. Modeling Source Water TOC Using Hydroclimate Variables and Local Polynomial Regression. Environmental science & technology 2016;50(8):4413-21. |
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Stewart, J.R., Livneh, B., Kasprzyk, J.R., Rajagopalan, B., Minear, J.T. and Raseman, W.J., 2017. A multi-algorithm approach to land surface modeling of suspended sediment in the Colorado Front Range. Journal of Advances in Modeling Earth Systems 2017; 9(7):2526-2544. |
R835865 (2017) R835865 (2018) R835865 (Final) R835603 (2017) |
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Stewart J, Rajagopalan B, Kasprzyk J, Raseman W, Livneh B. The Use of Ensemble Modeling of Suspended Sediment to Characterize Uncertainty. 17th Annual World Environmental and Water Resources Congress; 20172017. |
R835865 (Final) |
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Thurman EM, Yu Y, Ferrer I, Thorn KA, Rosario-Ortiz FL. Molecular Identification of Water-Extractable Organic Carbon from Thermally Heated Soils:C-13 NMR and Accurate Mass Analyses Find Benzene and Pyridine Carboxylic Acids. Environmental Science & Technology. 2020;54(5):2994-3001. |
R835865 (Final) |
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Hohner AK, Rhoades CC, Wilkerson P, Rosario-Ortiz FL. Wildfires Alter Forest Watersheds and Threaten Drinking Water Quality. Accounts of chemical research 2019;52(5):1234–1244 |
R835865 (Final) |
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Supplemental Keywords:
water quality, turbidity, hydrology, sediment transport, disinfection byproducts, water treatment, hydroclimate extremes, drought, statistical modeling, decision supportRelevant Websites:
As part of this project, the research team has developed an interactive visualization tool to enhance data exploration, and ultimately, treatment decision making.
The tool can be accessed using the following link: Optimization of water treatment operations for the Cache la Poudre River Exit
Progress 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.