Risk Management for Northeastern New Jersey Water Supplies

Suez Water New Jersey (SWNJ) depends on the Hackensack River Basin to supply drinking water for more than 1 million people in New York and New Jersey. The reservoir system consists of four reservoirs and multiple raw and finished water diversions that had been managed using operating rules developed in 1997. Since then, system demands and permit water allocation have changed, prompting the need to more effectively manage this critical resource.

The water industry has long relied on the concept of safe yield for reliability assessment and capacity planning. However, operators would never run their system to the safe yield for fear of running out of water, so rules are needed to reduce the risks. Operators often rely on storage-or elevation-based rule curves that lead to corrective action – like demand restrictions, cutbacks to downstream releases, or backup supplies-- but rule curves fail to account for the specific nature of individual droughts.

In a pilot study, SWNJ decided to adopt Dynamic Reservoir Operations (DRO), which rely on rules that change based on the state of the system and/or forecasted conditions, including rainfall and runoff, demands, and potential outages. They provide insight on the potential severity of the current drought and thus give operators a complete understanding of the risks to the water supply.

This presentation will describe the development and implementation of DRO using forecast-based operating rules for the Hackensack River Basin. DRO were put in place as a pilot in September 2014 and immediately demonstrated their value during extremely dry conditions that materialized in early 2015. They allowed for data-driven decisions to improve the timing of drought response and made the system more resilient and cost-effective.

In addition, the forecasts have been shared with state regulators. Regulators have recognized the use of DRO as a state-of-the-art practice and have been working with Suez to test their use. Based on the success of the pilot, Suez expanded the DRO to include all of its diversions, resulting in a complete transition from rule curves that had been in place for nearly 20 years to probability-based triggers. In this case, the triggers are based on an x% chance of reaching y% reservoir storage in the following z weeks, with each trigger resulting in corrective action to conserve storage. This is believed to be the largest system in the United States testing probability-based triggers for drought management. The use of DRO by SWNJ received an Innovation Award from Suez North America for its contribution to sustainable water management.