Harmful Algal Bloom Monitoring in Boulder County, Colorado

Harmful Algal Bloom Monitoring in Boulder County, Colorado

Nayoung Hur
August 15, 2023

Algal growth that causes hypoxic or toxic conditions are often referred to as harmful algal blooms (HABs), which are a public health concern. There are multiple ways to define HABs, but generally blooms are considered harmful when they (1) contain toxin producing algae and/or (2) are dense enough to deplete oxygen in the water. It’s important to know when HABs are occurring in our ponds and reservoirs but monitoring is typically based on visual observations, so the frequency of reporting is dependent on staff availability and cost.

Lynker worked with City of Boulder Open Space and Mountain Parks (OMSP) to monitor HABs in OSMP’s waterbodies using a combination of remote sensing and in situ sampling. We used two algorithms to track the prevalence of algal blooms and cyanobacterial outbreaks in Boulder County waterbodies. The NIR:Red measures the reflectance ratio between the near infrared and red bands to detect the presence of possible algal blooms on surface waterbodies. The dual-threshold Floating Algae Index (FAI) and Normalized Difference Water Index (NDWI) rule-based algorithm was used to indicate possible cyanobacterial blooms on surface waterbodies. This project accessed data from Landsat 5, 7, and 8 and the Sentinel 2A/2B satellites via Google Earth Engine to conduct the remote sensing assessment.

Results from this study revealed Sentinel 2A/B satellites were most effective in identifying water surface algae presence and spatiotemporal dynamics. In Sombrero Marsh, NIR:Red outputs reveal algae presence was observed most frequently near edges, which is typical of algal growth patterns. The FAI-NDWI results indicate potential cyanobacterial blooms were most observed in the center of the marsh (Figure 1).

Figure 1. These images summarize HAB monitoring from April to October 2021. In the image on the left, darker green colors indicate more counts of algae using the NIR:Red threshold. In the image on the right, darker green colors indicate more counts of cyanobacteria using the FAI and NDWI algorithms. Satellite imagery: © 2021 Google, CNES / Airbus, Maxar Technologies, Public Laboratory, U.S. Geological Survey, USDA Farm Service Agency.

The NIR:Red timeseries show data collected about every 5 days throughout the 6-month study period (Figure 2). We categorized image processing using three types of points for each waterbody (Edge, Near Edge, and Open Water) to remove the potential influence of shoreline vegetation. At Sombrero Marsh, NIR:Red peaked in the late summer, revealing a seasonality to algal growth.


Figure 2. Time series of the NIR:Red ratio at each sampling location and pixel type in Sombrero Marsh for 2021. The gray dashed line corresponds to a NIR:Red value of 1. Traces above this line are consistent with algae growth.

Remote sensing results from this study provided guidance for the management of Boulder OSMP waterbodies. By documenting algal growth in near real time, we can provide water managers with the information necessary to protect the community. With the growing impacts of climate change, HAB monitoring is essential to protect water resources and public health. 


Next Generation National Water Model

Lynker Contributions to the Next Generation National Water Model

Jordan Laser, Zach Wills, and Nels Frazier
April 13, 2023

Within the United States, we face a plethora of complex water issues that each involve unique physical environments with legal and economic consequences. In 2011 and in response to Nashville Floods of 2010, the Integrated Water Resources Science and Services Project (IWRSS) was created to address these multi-dimensional hydrologic issues. Since then, several tools such as numerical models (e.g., National Water Model) and databases have been built to supply researchers and other information consumers with hydrologic data and forecasting. However, the diverse nature of the hydrologic problem space imposes requirements on each of these tools that make interoperability difficult (i.e., languages, model conventions, resolution, location, etc.).

To address this problem, the Next Generation National Water Model (Nextgen NWM) aims to streamline the communication that allows for interoperability and as a result, makes accessing hydrologic data and modeling more efficient and generates utility for scientists and hydrologic data consumers. The Nextgen NWM is not a model itself, but rather a user-friendly framework that manages the various models and data on the back-end.

Lynker is developing the Nextgen NWM alongside the National Oceanic and Atmospheric Administration’s Office of Water Prediction and the Alabama Water Institute. To ensure the quality and value of this product, the development team implements rigorous software development practices such as Test Driven Development and Continuous Integration and Continuous Delivery. Due to the diverse resources of the potential users of the Nextgen NWM, the system is built to run in the cloud or locally in potentially heterogeneous computing architectures. In short, the NextGen NWM will soon be powering hydrologic model forecasts from the Office of Water Prediction for the entire United States. Check out the following links to learn more about the Nextgen project.

National Weather Model Streamflow Forecast (Image credit: NOAA OWP)

Louisville Fire

Louisville Wildfire

Graeme Aggett
February 1, 2023
Louisville Wildfire

Just one year ago on December 30, 2021, the Marshall Fire swept through the City of Louisville, Town of Superior, and unincorporated Boulder County, destroying and damaging more than 1,000 homes and over 30 commercial structures. In terms of structures lost, it was the most destructive fire in Colorado history. Wildfire risk isn’t just limited to forests and mountains and this event could be just a preview of how future events could impact city suburbs and infrastructure. For example, the Marshall fire rekindled concerns that parts of the electrical grid might be under increased risk amid drought and rising temperatures that will continue to warm and dry the state into the future. Those patterns will only intensify as human activities add greenhouse gasses into the atmosphere, further priming the landscape for extreme fire behavior and extending fire seasons. Nearly 3 million Coloradans live in fire-prone areas, referred to as the wildland-urban interface or WUI. That’s about half the state’s population.


Lynker has just been awarded a contract to examine the risks of wildfire to, and posed by, the City of Louisville’s public lands in and around the City, and identifying opportunities for wildfire mitigation in order to be more resilient in future events. We are very much looking forward to working with the City on this important project.

Atmospheric Rivers

Atmospheric Rivers

Graeme Aggett
January 21, 2023
California rainfall

A series of atmospheric rivers have delivered up to 10 inches of rain to Northern California, causing widespread flooding and scattered debris flows. At least three other storm systems are forecast by the NWS to be on the way in the next seven days, bringing more widespread flooding. While this intense rainfall brings a welcome dent to the drought that’s gripped California, the storms have barely taken the state out of being classified as being in an “exceptional” drought. It’s unlikely the years-long drought will be busted, but a deeper dent in the deficit is at the very least probable.