Most water utilities plan strategically to ensure that expected future demands can be met adequately with their water supply even during extreme climate events. Traditionally, this has been done under the assumption that the variability in streamflow (i.e., water availability) in the future will resemble the patterns observed historically. However, as climate warming intensifies the global hydrological cycle, relying on past observations and experiences alone is no longer sufficient for long-term planning and management. As a result, water resource managers are increasingly seeking relevant and credible information about future climate change.

Researchers at Carolinas Integrated Sciences and Assessments (CISA) are collaborating with representatives from a public water utility in North Carolina and their engineering consulting firm to assess the implications of climate change for long-range planning. Specifically, we are focusing on the potential changes in reliability of the utility's raw water supply over the next fifty years.

This analysis — informed by a bottom-up approach known as 'Decision Scaling' - began with modeling of the water supply system's sensitivity to climate and characterizing the changes in climate that threaten the system's ability to perform within pre-defined thresholds of acceptable performance. The resulting understanding of 'critical climate changes' is then used to tailor the information available from climate change projections to assess the plausibility of these changes occurring over the utility's planning horizon. The uncertainty in these projections will be characterized in terms of relative likelihoods of exceeding or not-exceeding system performance thresholds that are consequential for strategic planning.

By focusing on the system's vulnerability to climate, this type of decision-centric analysis is likely to address limitations of GCM-driven impact assessments in informing water resource decision making. This presentation will begin with a brief overview from the utility manager about their climate change- related information needs and questions. Then, CISA researchers will highlight the unique aspects of the analytical approach and present the tailored information produced about changes in the reliability of the utility's water supply. The discussion will also include how these findings might be integrated into the current long-range planning process.

This presentation will provide the approach being used as part of on-going efforts for regional water resource resiliency planning in Central Ohio. The Mid-Ohio Regional Planning Commission (MORPC), and their partners completed the Sustaining Scioto Study in 2015. Sustaining Scioto evaluated risks to the region’s water resources associated with climate change and with projected development. Adaptive management strategies were defined to improve regional resiliency. In 2017, a subcommittee was formed to address the short-term strategies identified in that study. One of the core strategies was to engage the municipalities and utilities throughout the region to establish a collaborative forum. This presentation will discuss both the importance and the challenges associated with regional resiliency planning. The large-scale issues associated with climate change, including both increases in temperature and in the volatility in rainfall, are best addressed on a regional basis. The vulnerabilities addressed in the study included degradation of water quality, increased potential for algal blooms as well as potential increased incidence of both extended droughts and extreme storms and flooding. Strategies used to engage the region will be shared along with the regional strategies being considered for implementation to reduce our risks and improve regional resiliency. Regional planning of this nature is a key part of resiliency and can also facilitate HUD and other grant funding for projects required to protect and maintain our water resources and infrastructure. By working together as a region, we can plan for and develop strategies to maintain both reliable water quantity and water quality as needed for the growth and healthy development of Central Ohio.

Available data sources, proposed methods and preliminary results of statewide water demand projections will be presented for municipal, agriculture, golf course, energy, industry, and domestic self-supply water use. Statistical methods estimating the effects of rainfall, temperature, and evapotranspiration on water demand will be presented. The audience will be encouraged to provide feedback regarding additional data sources which may be relevant to the study, the assumptions needed to support the proposed methods, trends or adaptation strategies which could be considered in the development of the projections, and the implications of meeting the projected water demands using surface water, groundwater, saline water, or reclaimed wastewater resources.