Elkhorn Slough: Detecting Eutrophication through Geospatial Modeling

Category: Land Cover Change and Disturbances
Project Team: Elkhorn Slough: Detecting Eutrophication through Geospatial Modeling
Team Location: Elkhorn Slough Ecological Forecasting

The Floating Algal Index (FAI) for April-November 2013 in the Elkhorn Slough, California Landsat 8 OLI imagery was analyzed to identify eutrophication hotspots. Image Credit: Elkhorn Slough team

The Floating Algal Index (FAI) for April-November 2013 in the Elkhorn Slough, California Landsat 8 OLI imagery was analyzed to identify eutrophication hotspots. Image Credit: Elkhorn Slough team

Irma Caraballo Álvarez
Abigail Childs
Kirsten Jurich

Dr. Juan L. Torres-Pérez (Bay Area Environmental Research Institute)
Dr. Sherry L. Palacios (Bay Area Environmental Research Institute)

Past/Other Contributors:
Chippie Kislik (Center Lead)
Martha Sayre


Elkhorn Slough in Monterey, California, has experienced substantial nutrient loading and eutrophication as a result of fertilizer-rich runoff from nearby agricultural fields. This study seeks to identify and track spatial patterns of eutrophication hotspots and the correlation to land-use changes, possible nutrient sources, and general climatic trends using remotely sensed and in situ data. Threats of rising sea level, subsiding marshes, and increased eutrophication hotspots demonstrate the necessity to analyze the effects of increasing nutrient loads, relative sea level changes, and sedimentation within Elkhorn Slough. The Soil and Water Assessment Tool (SWAT) model integrated specified inputs to assess nutrient and sediment loading and their sources. TerrSet’s Land Change Modeler forecasted the future potential of land change transitions for various land cover classes around the slough as a result of nutrient loading, eutrophication, and increased sedimentation. TerrSet’s Earth Trends Modeler provided a comprehensive analysis of image time series to rapidly assess long-term eutrophication trends and detect spatial patterns of known hotspots. Results from this study will inform future coastal management structures and provide greater spatial and temporal insight into Elkhorn Slough eutrophication dynamics.

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Daryl Ann Winstead (Mekong River Basin Agriculture) 18-08-2016, 17:17

Great project! Did the project partners have any sort of presence or in situ data that the project used? If so, how was the data used? Thanks in advance for your response!

Team Elkhorn 19-08-2016, 13:56

The project partners (ESNERR and MBARI) provided us with a lot of great in situ data that we used for the SWAT modeling portion of the project. We also used the in situ data to verify our results from the Earth Trends Modeler.

Nirav Nikunj Patel 18-08-2016, 09:53

Interesting that the McKlusky contributed the most about of nutrient loading out of any of the other areas…what type of industries operate in this area? Are they distinct from the other surrounding areas?

Team Elkhorn 19-08-2016, 14:00

Thanks for your question. The entire watershed is very small, so there may be a number of contributing factors that cause McKlusky to be the basin with the highest sediment and nutrient contributions. The primary reason that we can think of is that McKlusky basin is located near an unmuted tidal area (meaning that there is not a lot of tidal exchange and that nutrients & sediments are sitting for long periods of time) causing increased instances of sediment and nutrient loading and eutrophication.

Team Elkhorn

Amber Jones 22-08-2016, 14:03

That was an interesting finding… I was also trying to figure out exactly how that conclusion was reached. It appeared as if due to rainfall, elevation and land cover. I also was going to ask what the land use was. Is it highly agricultural? I’d like to see how the model inputs compare among the regions.

Darius Hixon (MCHD) 16-08-2016, 10:29

Great job on the video and project! Did TerrSet account for changes in weather patterns or temperature during the modeling process?

Team Elkhorn 16-08-2016, 14:36

Hi Darius,

The Earth Trends Modeler in Terrset did not account for changes in weather patterns or temperature. If given more time, this is something that could be added in, but for this project it was out of the scope of work. It would be interesting to see how those variables could affect eutrophication!

Team Elkhorn

Alec Courtright 16-08-2016, 09:54

Great work on your project and great job on the video! Were you able to find/did you notice any seasonal trends in your FAI images?

Team Elkhorn 16-08-2016, 11:04

Thank Alec,

We did find some seasonal trends in the FAI, but we decided not to include these in the final results since the seasonality had some issues. Our biggest issue was that most images from November through February were dropped from the study due to extensive cloud cover from the ‘rainy’ season. This made the results of seasonality not as strong as we would have liked.



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