Get Full Government Meeting Transcripts, Videos, & Alerts Forever!
Get email alerts on the Salinity And Breach Management topic
No spam. Unsubscribe anytime.
Advisory committee: recent breach flows drove large spring salt export; salinity likely safe this winter but requires monitoring
Summary
Committee data show a large salt export from the South Arm in spring 2024 correlated with stronger flows through both the new causeway breach and the West Breach. Presenters said current salt mass and modeled scenarios indicate salinity is likely within ecological targets this winter, but members urged higher‑resolution monitoring and contingency modeling.
The Salinity Advisory Committee heard detailed data showing a steep export of salt from the South Arm in spring 2024 and discussed what that means for managing the causeway breaches and long‑term salinity targets.
Presenters described October baseline conditions and a range of modeled futures. “Our October volume‑weighted concentration was about 122 grams per liter,” a presenter told the committee, and models using 2002–2022 climate data produced warm‑dry, average, and wet‑cool scenario ranges. The presenters said a large calculated salt export occurred between April and October 2024 and that the timing of that export correlates closely with increased discharge through both the new breach and the West Breach.
Phil, a presenter for the monitoring team, summarized the salt‑mass change: “We tracked a fairly gradual decline in salt mass from early 2022 until early 2024; then in spring this year we saw a much steeper, much more rapid calculated salt export out of Gilbert Bay.” He and other staff showed plots linking discharge spikes through the breaches to the timing of that salt loss. Committee members noted that reservoir operations, antecedent soil moisture and sediment transport also affected how much runoff reached the lake and therefore how much salt was exported.
Sampling showed shallow, highly saline bottom layers forming in places such as Carrington Bay. Presenters described thin (20–50 cm) bottom brine layers with salinities rising toward 165–170 g/L and anoxic conditions with a hydrogen‑sulfide odor at the bottom. Committee members debated potential sources for those pockets (density‑driven flows from the North Arm through the breach versus poreflow/permeability around the causeway).
After discussing model scenarios and monitoring gaps, the chair summarized the committee’s near‑term view: “So we will hold the firm where it is,” and the group agreed to continue monitoring and to develop contingency modeling and operational options in advance of next spring’s runoff. Members emphasized the need for higher temporal‑resolution salinity and discharge measurements at both the new breach and West Breach/Lakeside outflows, and for improved methods to manage instrument burial and sedimentation during spring high flows.
The committee framed next steps around (1) improving real‑time monitoring at key outflow sites, (2) incorporating reservoir‑operation logic and soil‑moisture inputs into inflow forecasts, and (3) developing targeted modeling runs to show precisely when and how berm modifications would be needed to import or export salt safely. The chair asked members to bring specific research ideas to the tech‑team meeting in December and to the January committee meeting that will focus on modeling and observed trends.
The meeting record shows no immediate change to breach geometry; instead the committee recommended targeted monitoring and scenario modeling to support any future operational decision.
