Download American Water Resources Association 2015 SPRING SPECIALTY

American Water Resources Association 2015 SPRING SPECIALTY CONFERENCE Water for Urban Areas: Managing Risk and Building Resiliency March 30‐April 1, 2015 Los Angeles, CA Tuesday, March 31 8:30 AM – 10:00 AM SESSION 8: Approaches to Address Uncertainties and Risk 1 Reliability Assessment of Salt Lake City Water Supply System by using a Dynamic‐ Probabilistic Systems Approach ‐ Erfan Goharian, University of Utah, Salt Lake City, UT (co‐
authors: J. Lillywhite, S. J. Burian) Water supply reliability in large cities includes different components such as water supply, stormwater management, wastewater collection, flood control, and other water sector activities. These systems are typically planned, designed, and operated to provide a reliable level of service to people. However, the challenges of complex feedback loops, uncertain behaviors, and limiting assumptions constrain the ability to adequately study the whole system. The dynamic nature of these urban water systems, the interconnections of the sub‐systems and their relationships with external factors (e.g., climate, urban growth dynamics) suggest an integrated water resources management (IWRM) framework may provide a useful approach to study, plan, and design integrated water systems in cities. IWRM is a framework which supports decision‐makers to evaluate risk among different management policies and practices to help meet objectives. Using IWRM, urban water managers and decision makers evaluate the effects of changes in demand patterns and climate conditions to assess the performance of their systems. In this study, GoldSim, a probabilistic, dynamic simulation platform, is used to combine the IWRM process with the uncertainty of key factors for the case study of Salt Lake City, Utah. The first part of the project involved building the integrated model of hydrologic, water supply, urban stormwater, groundwater, and water demand. The next step was to incorporate the IWRM model with the uncertainty of climate, urban growth, and policy drivers. The result is a framework that efficiently calculates supply reliability for the system as a whole. The model formulation, assumptions, and structure are presented along with results. Robust Risk Analysis, Bottom up Climate Preparedness, and Multi‐objective Optimization: The Future of Water Utility Planning – Enrique Triana, MWH, Global, Fort Collins, CO (co‐
authors: L. Basdekas, C. Paulson, K. Lusk, B. Gracely) The complexity of municipal water supply planning is increasing significantly with factors such as climate change, infrastructure vulnerability, demand uncertainty, a dynamic legal and regulatory environment, and changing social values to name a few. This complexity requires a robust framework for planning and decision making, in which future situations and potential solutions can be processed and evaluated simultaneously based on different objectives while accounting for the associated uncertainty. Colorado Springs Utilities (CSU) is currently finalizing its Integrated Water Resource Plan (IWRP) to address these complex planning factors across multiple time scales. A planning framework developed by RAND Corporation, called XLRM, was adopted by CSU as a basis for the IWRP. The XRLM framework has facilitated the identification of planning elements such as uncertainties (X), policy levers and infrastructure strategies (L) that ultimately combine in relationships (R) that impact water system response and corresponding performance metrics (M). The modeling framework developed at CSU allowed the IWRP team to consider tens of thousands of plausible risk factor combinations and the resulting impacts to our water supply system. Climate change impacts were considered by using a bottom up approach and stress testing our water supply system in order to search for possible sign posts for policy or infrastructure decisions. Finally, a state‐of‐the‐art multi‐
objective optimization model was coupled with the system simulation model to effectively and efficiently search for improved system performance metrics across a large subset of climate and other risk factors. The framework was used to help evaluate and compare the effects of uncertainties and management strategies in the long‐term for the multiple and sometimes conflicting management objectives. CSU was successful in designing and implementing the above described framework by bridging the gap between research and practice and mixing multiple methodologies. Relationships between CSU and academic institutions enabled more efficient application of complex analytical processes. While the use of these highly sophisticated analytical techniques were valuable, there is no substitute for human judgment of water system experts. Communicating the results to stakeholders and policy makers was critical and through a comprehensive public process we found the balance between communicating the right amount of technical information in order for them to understand the subsequent policy and decision tradeoffs. CSU's IWRP will be used to support strategic capital improvement program implementation through the coming decades by serving as a roadmap for the future. Aurora Water Resources Planning ‐ A Pragmatic Approach for Incorporating Uncertainty ‐ Edwin 'Chip' Paulson, MWH Americas, Inc., Denver, CO and Brian Fitzpatrick, Aurora Water, Aurora, CO (co‐authors: A. Rodriguez, B. Fitzpatrick) Urban water supply planning is an increasingly complicated endeavor due to uncertainties associated with a host of future conditions including climate, hydrology, population growth, conservation effectiveness, infrastructure integrity, and numerous other factors. These uncertainties create risks to the ability of municipal water utilities to provide the desired level of service in meeting customer demands. These risks are particularly acute in the semi‐arid Intermountain West, where water supplies are scarce, population growth is consistently high, and potential effects of climate change in driving toward a hotter/drier future are significant. This paper describes the Water Resources component of the Integrated Water Master Plan being developed by Aurora, CO, the third largest city by population in Colorado. Aurora is a rapidly growing community with a very complex water resources system spanning three major watersheds and including many reservoirs and conveyance systems. Intricate water rights administration rules under the prior appropriation doctrine create complex water allocation problems. Detailed water resources system models are used to simulate performance of water rights, reservoirs and conveyance systems. Aurora Water, Aurora's water utility, is applying a focused, scenario‐based planning process in which impacts of population growth, climate variability, infrastructure outages, and other factors are quantified using water supply system performance metrics of reliability, average short‐year supply, and resilience. The paper describes a systematic approach for the evaluation and ranking of system vulnerabilities that serve as the basis for developing robust portfolios of projects and programs to prepare for uncertain future conditions. Data management system tools and methods of displaying complex model results are presented. If available at the time of the presentation, projects and programs being considered by Aurora Water to meet its future water needs will be described. The approach and tools presented in this paper provide a template for other urban water utilities to address water supply planning under uncertainty. The Causes of Water Demand Uncertainty and Their Importance for Water Supply Risk Assessment and Management ‐ Jack Kiefer, Hazen and Sawyer, Marion, IL Forecasts of water demand serve as critical inputs to water utility and watershed planning efforts and decision making. Traditionally, water demand forecasts have been and continue to be used for identifying the timing and magnitude of future water supply needs. Over the last two to three decades, the growing recognition and emphasis on the amount of water that can be conserved through greater efficiency has also made forecasts important from a demand management perspective. The role of water demand forecasts in affecting decisions about water supply investments, including investments in "alternative" supplies such as enhanced efficiency and water reuse, leads to further implications for water rate making and pricing strategies. Together with available water supply development options, the demand forecast provides the basis for evaluating the reliability of water services. The provision of reliable supplies of adequate quality is a fundamental mission of US municipal water providers. Uncertainties about the future, as well as about the causes of historical and recent trends in water usage patterns, can affect (a) how long‐term water demand forecasts are constructed and (b) why long‐term water demand forecasts are seldom realized with very high degrees of accuracy. Inaccurate forecasts can lead to costs to water utilities, water rate‐payers, and even to the environment. Over‐building of supply and water treatment capacity can lead to stranded capital assets, higher water rates than might otherwise be necessary, and additional stress on watersheds. On the other hand, under‐investment can result in imposition of water shortage restrictions, economic damages from water shortages, as well as harm to the credibility of water supply managers. These risks, the ways they are affected by planning uncertainties, and how water systems cope present a complex challenges, which are rooted in uncertainties about the demand for water. Using the results of recent research conducted as part of the Water Research Foundation's Water Demand Focus Area, this paper will present a summary of the principal causes of uncertainty in forecasts of water demand. The paper will describe and show examples of the prospective impacts of weather variability, climate change, economic cycles, and long‐term changes in water efficiency on water demand. The discussion will describe how these influences can be modeled and integrated into water demand forecasting. The paper will show examples of how these uncertainties can be portrayed and used to assess water supply planning risks and will demonstrate the fundamental importance of recognizing and addressing water demand within the risk management paradigm.