2026 Harmful Algal Bloom Program

The Agency’s 2026 Algal Bloom Monitoring Program consists of two parts: Routine Monitoring and Event Response. Routine Monitoring is conducted at public-water-supply intakes, lake beaches, and public-water-supply intakes in Lake Michigan. Event Response investigates potential cyanobacteria blooms in lakes or streams where blooms may threaten public health. Samples are sent to the Illinois EPA Laboratory for cyanotoxin analysis.

Routine Monitoring

Illinois EPA intends to monitor the following waterbodies and locations:

Public-Water-Supply Intakes - Lakes
One microcystin, cylindrospermopsin, anatoxin-a, and saxitoxin sample per month in April/May, June, July/August, and October near public-water-supply intakes (Table 1).
Public-Water-Supply Intakes – Lake Michigan
Microcystin, cylindrospermopsin, anatoxin-a, and saxitoxin samples at four Lake Michigan intakes between May and November.
Lake Beaches
One microcystin and cylindrospermopsin sample per month in June, July, and August at a subset of lake beaches (Table 1).
Beaches - Lake County Health Department
Between May and September, the Lake County Health Department intends to collect a sample approximately every two weeks at fourteen lake beaches and one stream (Table 1).

Table 1. Routine Monitoring at Illinois Lakes

Region	Lake Name	County	Illinois EPA Lake Code	Sampling Focus
Northern Illinois	Humbolt Park	Cook	RHB	Beach
Central Illinois	Jacksonville	Morgan	RDI	Public Water Supply/Beach
Central Illinois	Gillespie New	Macoupin	SDU	Public Water Supply/Beach
Central Illinois	Greenfield	Greene	RDZF	Public Water Supply
Central Illinois	Canton	Fulton	RDD	Public Water Supply
Central Illinois	Mauvaise Terre	Morgan	SDL	Public Water Supply
Central Illinois	Vermont City	McDonough	RDM	Public Water Supply
Central Illinois	Palmyra-Modesto	Macoupin	RDZP	Public Water Supply
Central Illinois	Otter	Macoupin	RDF	Public Water Supply
Southern Illinois	Carlyle	Clinton	ROA	Public Water Supply/Beach
Southern Illinois	Wayne City	Wayne	RCT	Public Water Supply
Southern Illinois	SLM Side Channel	St. Clair	SOL	Public Water Supply
Lake County Health Department	Lake Barrington	Lake	RTZT	Beach
Lake County Health Department	Bangs Lake	Lake	RTG	Beach
Lake County Health Department	Lake Catherine	Lake	RTD	Beach
Lake County Health Department	Channel Lake	Lake	RTI	Beach
Lake County Health Department	Countryside Lake	Lake	RGQ	Beach
Lake County Health Department	Dunns Lake	Lake	VTH	Beach
Lake County Health Department	Fish Lake	Lake	VTK	Beach
Lake County Health Department	Island Lake	Lake	RTZI	Beach
Lake County Health Department	Loch Lomond	Lake	RGU	Beach
Lake County Health Department	Slocum Lake	Lake	RTP	Beach
Lake County Health Department	Tower Lake	Lake	RTZF	Beach
Lake County Health Department	Valley Lake	Lake	RGZM	Beach
Lake County Health Department	Dog Training Pond at Independence Grove Dog Park	Lake	UGH	Beach
Lake County Health Department	Lake Forest Pond at Prairie Wolf Slough County Forest Preserve	Lake	UHG	Beach
Lake County Health Department	Hastings Creek at Duck Farm Dog Pond	Lake	GWAA	Beach

Event Response

Event Response investigates credible reports of a potential cyanobacteria bloom. A credible report refers to a direct observation by Illinois EPA staff or observations and pictures submitted by the public to Illinois EPA via our Bloom Report Form.

Direct Observation
Illinois EPA field staff may collect a sample for microcystin, cylindrospermopsin, anatoxin-a, and saxitoxin when they observe a potential cyanobacteria bloom in a waterbody.
Response via Bloom Report Form
Illinois EPA may investigate reported potential cyanobacteria blooms. Response is dependent on availability of resources. Publicly owned lakes are prioritized.

Illinois EPA may apply a preliminary test to screen samples for the cyanotoxin, microcystin, but may include other cyanotoxins. When a toxin exceeds guidelines for recreation or drinking water, Illinois EPA notifies appropriate lake-management entities. Illinois EPA may perform follow-up monitoring based on availability of resources.