Building the Stormwater Harvesting Roadmap in San Diego

Date / Time:
Wednesday, Sep 16 1:30pm to 2:00pm
Location:
4
Track / Session:
Track: Resiliency and Sustainability / Session 7
Description/Abstract: 

Stormwater infrastructure has traditionally sought to efficiently convey runoff away from developed areas to reduce flooding risks in the built environment. Because this approach has been shown to degrade receiving waterbodies’ conditions, watershed planners are now striving to retrofit the landscape with storage and detention practices distributed throughout urban watersheds. These practices are designed to slow and treat runoff to preserve the quality of downstream water resources by restoring more natural hydrologic dynamics and functions back into our most developed watersheds.  The amount of storage that is needed to accomplish this is vast and the cost to treat this runoff is high. Given the magnitude of the investment required to transform the hydrologic footprint of urban watersheds, it is imperative that watershed planners fully evaluate the possibility of leveraging this valuable resource to help recoup investment costs and help to augment local water supplies. This is ever more important in the already water-stressed cities of Southern California who seek to bolster municipal water resilience under uncertain climate futures.

The City of San Diego has undertaken a systematic investigation of potential stormwater harvesting strategies to identify strategically viable options and to quantify their costs and yield potential city-wide.  Unlike some other regions that can leverage ample groundwater storage as an endpoint for captured stormwater, San Diego is largely dependent on surface reservoirs for longer-term storage, and therefore requires creative and customized solutions to maximize annual water yield. This work follows on a regional study at the County level to determine the most advantageous harvesting alternatives that fit within existing stormwater management efforts, that offer the greatest returns to offset local water needs, and that can be accomplished at the most cost-effective scale.  Programmatic assessment, modeling and optimization, and stakeholder engagement were used to identify the stormwater harvesting approaches with the greatest potential for the City from the following alternatives:

·         -

Infiltration or Injection to Managed Groundwater Aquifers

·         -

Augmentation of Natural Hydrology through Infiltration

·         -

Capture and Reuse for Irrigation Demand

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Small-scale On-site Capture and Use

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Enhanced Natural Conveyance and Amenity

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Dry-Weather Diversion to Wastewater Treatment

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Capture/Discharge of Dry/Wet Weather to Wastewater/Advanced Treatment

·         -

Capture/Discharge of Dry/Wet Weather to Recycled Water Streams

Results of this study will be used to develop a robust approach to stormwater harvesting and use that will guide future stormwater management approaches, treatment options, and coordination with other water-related departments to move toward a shared vision for unified water cycle management across the City of San Diego. 

Primary Speaker:
Chad Helmle, Craftwater Engineering, Inc.