How to Integrate Climate Change Risks into Water Planning
Elvis Asong, PhD
Senior Climate Change Scientist.
It is now unequivocal that anthropogenic climate change presents substantial uncertainty to the Canadian water sector. Risks related to this uncertainty has grown as the 21st century progresses, along with the recognition that these risks must be factored into the design, construction, location, and operation of key water sector infrastructure and water resource planning. But how do water resources managers and professionals plan for uncertain climate change magnitudes and timelines? This challenging question often leads to adoption of a “wait and see” holding pattern, in the hope that climate science can be improved, and uncertainties narrowed before decision-making becomes urgent. However, postponing an honest assessment of climate change risks and assuming a business-as-usual approach to water resources planning and management is a risky proposition. Since it is certain that the global climate is changing, planning that assumes a constant climate from the past, present, and into the future is, unfortunately, flawed. Additionally, uncertainties affecting the local conditions that matter most to the water sector are not likely to be greatly reduced – at least during the design life of typical water sector investments – by further scientific study of global climatic processes. Indeed, a fraction of this uncertainty stems from natural climate variability or ‘noise’ that no amount of study will constrain. In short, there is no time like the present to begin factoring climate change into cold regions water sector decision making, even considering uncertainty in the magnitude of future change.
Growing awareness of climate change impacts, vulnerabilities and risks to Canadian water infrastructure parallels growing pressure from federal agencies (e.g., Infrastructure Canada), public financial institutions, commercial banks, and private sector insurers to ensure that developers of physical assets and infrastructure are adequately integrating climate resilience into planning and projects. To this end, governments and development agencies have invested considerable efforts to develop methodologies and tools to screen their projects for climate change risks. These approaches are linked by a common theme of risk assessment and are being rapidly adopted into operational water resource planning.
This article summarizes conventional approaches which can be adopted in practice by the water sector for incorporating considerations of climate change impacts and adaptation within existing modalities for project design, approval, and implementation. Also, recommendations are made for selecting a suitable approach or a combination of approaches for climate risk assessment.
Integrating Climate Change Adaptation into Water Management
Several approaches exist for mainstreaming climate change considerations into water sector decision making. These approaches on one hand reduce risks posed by climate change, and on the other identify opportunities that climate change may provide. Full consideration of climate change in the context of water infrastructure would typically combine an assessment of climate change risks/opportunities (and lead to potential ‘climate adaptation’ options), with assessment of project greenhouse gas emissions (and lead to potential greenhouse gas reduction ‘climate mitigation’ options). The focus of this article is on the former, which, if carried out carefully can guide water resource infrastructure design that is resilient to climate change-driven evolution of existing, new, and interdependent risks.
Approaches for incorporating climate change considerations in water resource projects
Risks of climate change to water sector investments are identified through conducting Climate Change Vulnerability and Risk Assessments (CCVRAs). Two main approaches are applied to conduct water sector CCVRAs: climate scenario-driven impact assessment approaches, often referred to as “top-down” or “predict-then-act,” and vulnerability-oriented approaches, often called “bottom-up” approaches. “Top-down” methods focus first on future climate data from Global Climate Models (GCMs). This information is fed into impact models (e.g., hydrologic and water management models to estimate potential impacts) or mapped against the locations of project options (or existing assets) to determine vulnerability and risks and potential adaptation measures.
Conversely, “bottom-up” approaches go beyond “climate downscaling” and focus first on finding adaptation options which reduce water system vulnerability to past and present climate conditions, and also recognizing major non-climatic impacts on these systems, including water management policies, stakeholder constraints, and environmental regulations. This approach targets critical existing vulnerabilities and tipping points in the system – including other factors that influence system performance – to ensure that that climate risks are not assessed in isolation. Robust adaptation measures are then identified that would reduce vulnerability under current climate conditions, while also being acceptable technically, financially, economically, socially, and environmentally.
If the lifetime of the project spans several decades (e.g., water and wastewater treatment plants, stormwater management systems, and urban water supply systems), climate models can be used to establish upper and lower bounds for climate change sensitivity testing of vulnerability-driven “bottom-up” adaptation scenarios. This “hybrid” approach aims to identify adaptation steps that perform well over the range of conditions that are experienced both now, and into the future. An example of a robust “hybrid” tool for climate risk assessment of water sector infrastructure is the Public Infrastructure Engineering Vulnerability Committee (PIEVC) Engineering Protocol, first developed by Engineers Canada and now managed by the Institute for Catastrophic Loss Reduction.
In practice, predict-then-act, test existing vulnerabilities or a combination of both?
Water sector projects are often technically challenging, and undertaken against a complex landscape of user needs, and priorities. Project specifics should first and foremost dictate an appropriate CCVRA approach (Figure 1). The expertise required to select and undertake a suitable CCVRA method is multidisciplinary and organizing an appropriate CCRVA team can be a challenging aspect of water sector-based climate adaptation. The method that the team applies must be scientifically sound, economically viable, and socially beneficial. It should also use risk management methods (for example, the internationally-recognized ISO 31000, risk management guidelines) as an underlying principle that can be used to manage uncertainty that is inherent in future climate projections. Finally, it should recognize that impact (“top-down”) and vulnerability (“bottom-up”) assessments are complementary processes that can be successfully combined into “hybrid” approaches that daylight the potential range of impactful future changes, consider project component vulnerabilities to existing pressures, and identify critical climate change risk thresholds.
The extent to which climate change projections are used to inform water sector project designs depends on the vulnerability of the design to climate conditions, and on the quality of future projections of these conditions. Sometimes, the nature and magnitude of projected climate change conditions are relatively well understood. Consider a city that intends to design a wastewater outfall into the ocean. Climate projections indicate that sea level will almost certainly increase – although the local rate of increase may not be known with high confidence. In this case, applying the higher end of the range of projected sea level rise over the project lifetime is arguably appropriate, unless there are significant incremental costs or performance issues involved in doing so.
In contrast, complex projects – such as design of water treatment plants – involves aspects such as water supply and demand modelling, calculation of water quality treatment needs, and assessment of vulnerability to weather and climate extremes. Consideration of climate change impacts to each of these factors involves substantial uncertainty in future conditions. In such cases, strong assumptions about future values of these variables may lead to improper design, water treatment plant underperformance, and possibly mal-adaptation to future change. Under these circumstances, a “bottom-up” approach that relies less on quantitative future climate projection information could be more appropriate. In some cases, climate change uncertainty may be so great that responding to it seems impossible. In this case, scenario planning (a widely used technique that embraces uncertainty rather than trying to reduce it) can be adopted to envision the full range of possible futures that may unfold. Futures may be near‐term and simple (e.g., what if the highest projected annual temperature occurs in the spring?) or they may be long‐term and complex, addressing the interactions of highly uncertain drivers (e.g., what if a over the next 70 years a community consistently gets the highest projected precipitation and the budget for water and wastewater plants is cut in half?).
Combining “top-down” (impact-driven) and “bottom-up” (vulnerability-driven) climate risk assessments is suitable for many water sector projects, many of which already require an integrated management framework. Initial project scoping can identify the climatic and hydrological conditions of interest to project designers. These are typically the conditions that guide engineering design (e.g., mean and variability of annual river discharge), as well as conditions associated with hazards to the project (e.g., peak flood discharge). The impact assessment will involve developing plausible assumptions about the behavior of these variables of interest over the project’s future life span. This can involve analysis of observed weather and climate conditions, climate model projections, or conditions that are already experienced at other sites (so-called ‘analog locations’). Key to this information gather is interpretation of changes in primary meteorological variables with respect to the more complex – but often more design-relevant – hydrologic phenomena such as floods, drought, and water quality.
The CCVRA will then work to establish causal relationships between anticipated impacts of climate change and the performance and integrity of each element of the project. An important outcome is a clear understanding of whether climate change will cause key physical and economic risk thresholds related to performance, structural integrity, and life safety, to be surpassed. At the most comprehensive end of the CCVRA spectrum, detailed impact modeling may be required to identify interactions and interdependencies between project components and climate variables to understand the potential for interacting and cascading impacts and related risks. Conversely, much simpler qualitative assessments can still provide very substantial benefits in terms of risk identification and prioritization, especially when impact modelling and full quantitative risk assessments are prohibitively expensive.
Climate change uncertainty is no reason for inaction or delaying CCVRA activities. Indeed, CCVRAs undertaken across numerous water investment projects have demonstrated that such assessments:
- Can be undertaken within a reasonable time frame and with limited resources;
- Provide excellent understanding of how water resources projects can be affected by ongoing and future climate change;
- Can point to a wide selection of “climate proofing” adaptation measures;
- Can increase climate resilience of an investment project, often without requiring fundamental changes to project design; and
- Do not necessarily require large incremental costs to project investment.