By U.S. EPA
Natural disasters such as floods, drought, hurricanes, winter storms, and earthquakes can interrupt access to clean drinking water. To improve their resilience, communities, and the utilities that provide drinking water to these communities, are building their capacity to return to service as quickly as possible, planning for and understanding any potential vulnerabilities in their system, and practicing response to adverse events in real-time as they happen.
To help communities and their drinking water utilities, researchers from EPA and Sandia National Laboratories developed the Water Network Tool for Resilience (WNTR), a comprehensive scientific software package to help assess a drinking water systems’ resilience to natural disasters. The software improves upon already available capabilities by fully integrating hydraulic and water quality simulation, damage estimates and response actions, and resilience metrics into a single platform. The software is available as an open-source software package and can be applied to a wide range of disruptive incidents and repair strategies.
“The WNTR software package can help drinking water utilities estimate potential damages from a disaster, understand how the damage to infrastructure might occur over time, evaluate preparedness strategies, prioritize response actions, and identify worse case scenarios and efficient repair strategies,” explains EPA researcher Terra Haxton. “WNTR includes a variety of models, it has flexible controls, hydraulic simulations, and resilience metrics and it is compatible with EPANET, EPA’s software application that is used worldwide to understand the movement and fate of drinking water within a distribution system.”
EPA researchers have already applied this tool to a number of scenarios requested by state and local utilities to assist them in both preparing for future disasters and in the recovery of past events. In 2017, EPA began working with Poughkeepsie Water Treatment Facility to investigate the resilience of their drinking water system. This treatment facility supplies water to both the City and Town of Poughkeepsie, NY. The facility asked the researchers to assess a scenario involving the loss of the source water to the treatment plant that could be caused by a variety of incidents, such as frozen intake pipes, due to a winter storm event, a drought, or a saltwater intrusion event. The water utility managers were interested in evaluating how long they could continue to supply water to their customers, and the effectiveness of strategies, such as reducing usage, at extending the timeframe in which water would continue to be available to customers.
The researchers worked with the water treatment facility to analyze a scenario investigating breaks in critical distribution pipes and how it would affect firefighting capability. WNTR can assist with this analysis because it includes a feature that simulates the movement of water under low pressure conditions as it travels from the utility to businesses and residences throughout the system. This analysis was shared with the City and Town of Poughkeepsie which will use these results to plan the costs of system upgrades that would enhance resilience over the long-term.
That same year, the active hurricane season in the Atlantic brought two Category-5 hurricanes to the U.S. Virgin Islands within a two-week period. These storms caused significant damage to the critical infrastructure systems providing energy, water, transportation, telecommunications, and healthcare. In response to the devastation, government agencies, communities, and long-term recovery groups in the U.S. Virgin Islands are developing hazard mitigation and resilience plans.
In May 2020, the Naval Postgraduate School (NPS) approached EPA staff and researchers to partner in their resilience study of the U.S. Virgin Islands Water and Power Authority (WAPA), which supplies drinking water to the St. Croix, St. Thomas, and St. John islands. The researchers used WNTR to analyze four-week power outage scenarios caused by hurricanes on the WAPA systems. The impact of a power outage on a drinking water system is important to drinking water utilities. WNTR can help determine the effects of a power outage by simulating the removal of pumps and tanks from the system operations and can simulate the impact to customers and help identify where to invest in back up power. NPS brings expertise in electrical power resilience, and with EPA researchers, they are addressing the interdependencies between water and power systems. The results will be used by the utility to develop a hazard mitigation and resilience plan to address future hurricanes.
WNTR is used to estimate potential damage and understand how damage to infrastructure would occur over time. It can also be used to evaluate preparedness strategies, prioritize response actions, and identify worst case scenarios, efficient repair strategies, and best practices for maintenance and operations. Additional community applications of WNTR include the U.S. Army Fort Campbell installation on the Kentucky/Tennessee border and the Pittsburgh Water and Sewer Authority (PWSA) in Pittsburgh, PA.
WNTR is being used to analyze the ability of the Fort Campbell system to provide water for a minimum of 14-days following extended outages as established in the Installation Energy and Water Security Policy (Army Directive 2017-07).
PWSA is interested in applying WNTR to evaluate the resilience of their system of infrastructure failures (e.g., pump stations, 60-inch water mains, clearwell) as well as the potential consequences of landslides. Four case study applications of WNTR will be made available to the utility and the public, with the first two available in the next year focusing on the U.S. Virgin Islands and the City and Town of Poughkeepsie. Researchers are compiling information that can be used by other water utilities across the country to understand how they can employ resilience strategies to mitigate damage to critical infrastructure by disasters.
Utilities must also meet certain requirements set out in law, specifically the America’s Water Infrastructure Act of 2018 (AWIA). AWIA requires community (drinking) water systems serving more than 3,300 people to develop or update risk assessments and emergency response plans (ERPs). The law specifies the components that the risk assessments and ERPs must address and establishes deadlines by which water systems must certify to EPA completion of the risk assessment and ERP. WNTR can assist utilities in identifying vulnerabilities to their systems and determining mitigation measures that best meet their needs.
For more information about WNTR, please visit: https://github.com/USEPA/WNTR
Klise, K.A., Bynum, M., Moriarty, D., Murray, R. (2017). A software framework for assessing the resilience of drinking water systems to disasters with an example earthquake case study, Environmental Modelling and Software, 95, 420-431, doi: 10.1016/j.envsoft.2017.06.022