A vulnerability analysis helps water utility operators spotlight areas where they are most vulnerable to climate change and lay the groundwork for follow-up prioritization and action. Many water utilities have initiated efforts to investigate their vulnerability to climate changes processes. Such efforts attempt to craft a systematic characterization of how climate change impacts will affect the operation of specified utility assets and operations within a specified time period, usually 20–50 years.
A vulnerability analysis relies on a number of key attributes, including the location of the watershed and its predominant characteristics, the different sources of customer demand, the role of storage in meeting customer demand, the diversity of water supply sources, the current flood management operations, assets and their condition, how regional water resources are shared, and water quality impacts.
Vulnerability analyses generally adopt one of two broad approaches, referred to as “top down” or “bottom up.” The “top down” approach relies on downscaled global climate change models that are used to forecast impacts on water quality and supply. These projected impacts are then used to inform future water resource planning. The “top down” approach is limited by the resolution of global climate change models, since they generally do not forecast impacts at a spatial scale small enough to be relevant to an individual utility.
The “bottom up” approach involves water utilities identifying likely “cause-effect” pathways where they would expect climate change to impact their assets or operations. The utility can then apply existing water resource management tools to determine how climate impacts will effect vulnerable operations. This approach allows utilities to evaluate current water resource management activities in the face of a reasonable (20–50 year) planning horizon.