Abstract

Global climate change has been forecasted to have significant impacts on water supplies throughout the US, particularly those using watersheds that contain considerable snowmelt. If many of these predictions are true, substantial investments in water supply infrastructure will be required in the future simply to meet today's water demands. To date, few water supply managers appear ready to make such infrastructure investments based on climate change predictions. Given the time required to design, permit, and construct new infrastructure, if climate change forecasts are correct, many water supplies may run short of water before new sources can be brought on-line.

The reluctance to develop costly new infrastructure based upon climate change forecasts presents a very interesting conundrum. Water managers often make infrastructure decisions using data that are either uncertain or speculative. Water demand forecasts, streamflow data, and system operations all contain uncertainties and inaccuracies, however, they are generally incorporated into the decision making process without hesitation. Concerns about climate change, however, appear to be sufficiently significant to prohibit their inclusion. One is left to ask, exactly how uncertain is climate change and its impacts relative to other uncertainties that we typically deal with?

The paper traces uncertainties that are associated with four stages of data and information: streamflow data, rainfall-runoff models, demand forecasts, and management models. Such an evaluation is necessary to allow water managers to determine the importance of climate change relative to other factors that they typically consider and whether the certainties associated with climate change are so great that it should not be considered in their infrastructure decisions.