Information Management System for Water Right Mitigation Compliance: City of North Bend

New groundwater appropriations in many parts of Washington State are subject to minimum instream flow restrictions.  In areas where there is hydraulic continuity between groundwater and streams, developing new groundwater rights has been subject to intense scrutiny and uncertainty, particularly for municipal providers.  Groundwater under the City of North Bend, located in Western Washington, is in hydraulic continuity with the Snoqualmie River. The City obtained a new groundwater right in 2008 with a requirement to mitigate for the impacts from its withdrawals.  The mitigation is based on a contract purchase of water from an adjacent watershed and direct transfer of that water into the Snoqualmie River on days that minimum instream flows are not met.

The City’s daily mitigation requirement is determined using a series of analytical stream depletion calculations, performed on a daily basis, that estimate the City’s impact from the past 20 days of pumping.  A variety of real-time data are necessary to implement the calculations.  We therefore developed a web-based system to collect the necessary inputs, perform the calculations, and direct the City’s personnel on daily water system operations.  The system interfaces with the City’s telemetry system and also monitors USGS real-time streamflow to determine instream flow status.  The system stores the data associated with over 90 variables, including the inputs to the calculations and the results.  The system is designed to produce a variety of monitoring reports that are submitted to demonstrate compliance with the conditions of the water right.  Event reports, quarterly reports and annual reports are automatically generated using the database system.    

The mitigation requirements for the City’s water right are currently one of the more complex requirements developed in Washington State.  However, the online database enables the City to manage its mitigation requirement on a daily basis with the click of a button.