Thresholds that Matter for Water Utilities when Confronting Floods and Drought

Drawing on recent experiences from two water utilities, we will illustrate the decision points at which resource managers can incorporate considerations of flood and drought risks into their work. These cases offer concrete examples of how decision-makers can gain value by identifying key operational, design, and hydroclimatic thresholds that exist within the systems for which they are responsible.

For the flood case, American Water has a number of facilities in the Northeast that have been affected by tropical storms (Irene, Sandy) in recent years. Some of these facilities have been able to withstand the floods that accompanied these storms, while others have suffered significant damage. We will describe how these experiences have informed American Water's view of the historical flood and rainfall records and its perception of flood risk. We will focus on how this new understanding of flood risk has subsequently impacted design specifications of infrastructure and flood impact thresholds. We will describe American Water's strategy in making infrastructure design decisions for the future, given the relatively long lifetimes expected for this infrastructure.

For the drought case, East Bay Municipal Utility District (EBMUD; California) has been engaged in a research project about the energy intensity (amount of energy required to supply a unit quantity of water) of its drinking water and wastewater services. By examining the spatial and temporal variability in energy intensity, EBMUD has been able to identify times of year, times of day, and areas within the service region where energy intensity is greatest, and can use this information to better manage its overall energy consumption. This information can also be useful in understanding and identifying operational thresholds that exist within drought periods. It provides estimates of “non-linear” energy consequences of managing the water system during droughts, as the supplemental water resources that are brought online often have relatively high marginal energy intensities, due to the long distances required for conveyance. Given the fact that both water and energy supplies can be stressed by drought conditions, and the interchangeability of water and energy, this insight could galvanize efforts to increase water and energy efficiency, or develop new sources of energy that consume less or no water.