Overview

Long-term ecological surveys have been a core function of the Interagency Ecological Program (IEP) since the program’s inception in the 1970s. The IEP Seasonal Monitoring Report presents the full time series for selected water quality, plankton, and fisheries surveys conducted by IEP in a single graphical report. The report is generated on a quarterly basis, with different set of ecosystem variables and surveys highlighted in each season. The report is developed by IEP scientists (including leads for monitoring surveys and the IEP Lead Scientist) and is reviewed by the IEP Science Management Team and Coordinators before online publication.

This report was last updated in October of 2026, with available data through 2025.

Not all data from 2025 are complete, zooplankton data from 2025 are still pending, and the Adult Sturgeon Study and SKT are no longer in operation.

Water Year Summary

Table of Contents

Spring

  • Delta Outflow
  • Secchi Depth
  • Water Temperature
  • Chlorophyll
  • Zooplankton
  • Fish
  • Recent Trends

Summer

  • Delta Outflow
  • Secchi Depth
  • Water Temperature
  • Chlorophyll
  • Zooplankton
  • Fish
  • Recent Trends

Fall

  • Delta Outflow
  • Secchi Depth
  • Water Temperature
  • Chlorophyll
  • Zooplankton
  • Fish
  • Recent Trends

Winter

  • Delta Outflow
  • Secchi Depth
  • Water Temperature
  • Chlorophyll
  • Zooplankton
  • Fish
  • Recent Trends

Metadata

  • Report Information
  • Overview
  • General Information
  • Data Sets
IEP logo

Figure 1: IEP logo

Disclaimer: While substantial efforts are made to ensure the accuracy of these data, complete accuracy of data sets cannot be guaranteed. This report was developed by the IEP Synthesis Team. For questions, comments, or corrections, contact Rosemary Hartman –