Climate Variability

Why It Matters

Water management and climate change are inextricably linked. The impacts of climate change such as sea level rise and increases in frequency of extreme weather events, directly affects water sources and infrastructure. The number and frequency of droughts, severe storms and wildfires has intensified over the past 20 years. Further, the U.S. Geological Survey has linked river salinity to climate change. The changing of source water makeup and extreme weather events directly impacts the environmental aspects of our business.

Infrastructure that is in poor condition or designed for historical environmental conditions is more susceptible to the impacts of extreme weather events, especially flooding and droughts, which can result in contamination or loss of service. Water utilities must address these risks through redundancies and strategic planning. This work is vital to continually meet our customers’ basic needs for clean, safe and reliable water while also promoting shareholder value.

We invest in the resiliency of our systems and the communities we serve. The effects of floods, fires and hurricanes across our country have devastated many of our communities. Challenging weather conditions, and thus the related risks, are predicted to continue and escalate. In 2017 alone, there were $17 billion of natural and climate disasters in the U.S. The Northeast has seen five to seven 100-year floods or natural disasters in the past decade.


Our Approach

To prepare our water and wastewater utilities for the future, there is an increased focus on incorporating climate change into our Asset Investment Strategy. We manage risks and opportunities related to climate change, particularly with respect to extreme weather events and community resilience, and share best practices with the industry. We protect the viability, integrity and resiliency of water supplies and water and wastewater infrastructure in areas that are vulnerable to droughts, floods and extreme weather events. Adapting to increasing climate change means we must identify solutions that improve our management of related risks for the communities we serve.


See Water Supply Resilience for details about our approach to adaptation and mitigation strategies associated with climate change.


Our Capital Program Management Policy requires that investment in our infrastructure follows specific recommendations from our comprehensive asset planning process, which includes assessing risks from climate change and developing appropriate mitigation and adaptation strategies. For example, in our construction, we use either a 100-year minimum or 500-year flood elevation as the basis of design, depending on the criticality of the asset and specific application.

New Mississippi

Floodwall in Iowa Continues to Protect Plant as Waters Rise, Resiliency Planning Helps When Natural Disasters Occur

Recent flooding on the Mississippi River continues to set new records. As the water rose, Iowa American Water employees worked around the clock to continue to provide water service to customers. While flooding is not a new challenge, in 2019 the river rose to a record-setting 22.7 feet above mean sea level (AMSL). Additionally, due to heavy rainfall, the river crested for a second time one month later at 21.7 feet AMSL.

Resiliency came in the form of a permanent 2,200-foot long floodwall established in 2013 by a partnership between Iowa American Water, the Army Corps of Engineers and the City of Davenport. We constructed the original floodwall after the Hurricane Floyd in 1999, which inundated the plant and interrupted water supply to customers for weeks. The preliminary engineering work to increase the level of flood protection above the original floodwall level was initiated following Hurricane Irene in 2011, when floodwaters came within an inch of overtopping the floodwall. The $11.8 million floodwall, constructed in 2013, is designed to protect the water treatment plant to a river stage of 31.4 feet AMSL. The floodwall closed when the river level rose to 20 feet on April 15, 2019. This was the first major flood event to test the wall since its completion.

During all Mississippi River flooding events, we kept our treatment facility protected and in service, with water flowing to our customers. This plant runs on a single source of water, which can present a host of challenges, including the potential for 55,000 connections to go without water service in the event of a significant flood. However, the floodwall alleviated some of that risk, allowing the plant to stay in service. This is proof that funding for resiliency capital projects benefits communities.

Planning for Climate Impacts

Our operations and engineering teams meet regularly to develop long-term capital plans that address our systems’ safety and resiliency. We will continue to invest in our resiliency because we see the readiness of our systems as critical to addressing weather challenges and climate change impacts on our life-sustaining services.

Through a comprehensive planning process, we evaluate how water supplies, water quality and water demands may change. We also evaluate how storm intensity could affect our assets, and whether we need to update our design standards. We incorporate increasing climate change into our water usage models and mitigation strategies to reliably serve our communities.

When we build new facilities, we consider climate change, raising critical equipment well above historic flood levels and designing for more frequent and intense weather events to strengthen their resiliency. We have committed approximately $1.5 billion annually to upgrade and renew water and wastewater treatment plants, distribution and transmission pipes, pumping stations and other essential facilities. Approximately, 8% of our capital investment is dedicated to resiliency.

Global Issue, Local Impacts

Climate change affects each of our subsidiaries’ geographies differently. In coastal communities where we rely on both surface water and groundwater, our surface water supply is affected by sea level rise and more frequent flooding, while wells may be vulnerable to increased salinity. We develop strong relationships with local municipalities

to help ensure we can address any issues when flooding or other climate-related issues arise. Coastal wastewater systems also can experience increases in inflow and infiltration from more intense storms and flooding.

Another critical risk is water supply depletion, so we carefully monitor the water levels to help ensure operational efficiencies when pumping and utilize technology to identify any impacts on the aquifer. We use groundwater models, often from individual state versions of the U.S. Geological Survey, to monitor the amount of water in the aquifer to help ensure withdrawals match refills.

Across all geographies, development activity further magnifies the effects of climate change. As land is developed for housing and other uses, increased impervious surfaces generate more runoff, resulting in increased flooding and risk of introducing new potential contaminants to water supplies. Understanding that this trend will continue, we support responsible state and local planning and zoning policy that protects our water resources. See Policy Influence for additional information.


Intense storms and winds can lead to power outages that could affect our services. We must be prepared for these events by ensuring our most critical facilities can operate on stand-alone power generation sources for an extended period of time, such as natural gas-powered generators and/or solar panels. Additionally, our Emergency Response Plans focus on strategies to mitigate the potential impact from extreme weather and climate change to improve the reliability of our systems for the benefit of our customers



Our Performance

At American Water, as part of our long-term capital planning, we assess climate variability impacts on our most critical assets and upgrade accordingly. During this process, we conduct assessments to evaluate risks of equipment damage due to flooding concerns. For collection systems, we conduct flow monitoring, hydraulic modeling, CCTV and other inspections to identify sources of Inflow and Infiltration (I&I). We make recommendations to improve resiliency and service delivery, and reduce I&I.

Since 2015, at least 75% of our systems have not experienced any End of Pipe (EOP) exceedances and over 77% of our systems did not experience any sanitary sewer overflows (SSO).

Code Accounting Metric 2015 2016 2017 2018
IF-WU-450a.1 Wastewater Treatment Capacity Located in 100-Year Flood Zones (Cubic Meters (m³) per Day) 110,248
Total Systems 167 171 168 173
Systems Without Any EOP Exceedances 75% 80% 82% 76%
Systems Without Any SSOs 78% 85% 77% 77%
End of Pipe (EOP) Exceedances 163 121 175 162
Number of Sanitary Sewer Overflows (SSO) 99 82 133 127

We disclose the material financial implications and other risks and opportunities due to climate change in our CDP response as well as the Annual Report. We use the outcomes of our risk analysis to identify at-risk infrastructure and invest in resiliency measures.