One measure of a lakes health is the trophic state, which relates to the amount of algae in the water. The average summer trophic state for the last 5 years was 45 (Mesotrophic) and was determined using chlorophyll data. For a Two-Story lake, this is considered Good.
Green Lake was monitored by volunteers between 1986 and 2018. Volunteers monitor water clarity with a black and white Secchi disk. Some also collect water samples, which are sent to the State Lab of Hygiene to be analyzed. Volunteers are the source of the majority of Wisconsin's lake water quality data, and their dedication is greatly appreciated. Additional monitoring has been done through projects funded in part by DNR Lake Grants and Aquatic Invasive Species Grants. Reports and graphs featuring data collected by volunteers, DNR staff and others can be viewed below.
| Station Name | Station ID | Map | Max Year | Reports |
|---|
| City Millpond - Channel North (Herbicide Monitoring Site 5) | 10042074 | Map | 2015 | Details |
| City Millpond - Channel South (Herbicide Monitoring Site 1) | 10042070 | Map | 2024 | Details |
| City Millpond - Eddy Mid (Herbicide Monitoring Site 4) | 10042073 | Map | 2015 | Details |
| City Millpond - Eddy North (Herbicide Monitoring Site 6) | 10042075 | Map | 2015 | Details |
| City Millpond - Eddy South (Herbicide Monitoring Site 2) | 10042071 | Map | 2015 | Details |
| City Millpond -Channel Mid (Herbicide Monitoring Site 3) | 10042072 | Map | 2015 | Details |
| County K Marsh - Big Green Lake | 10044125 | Map | 2017 | Details |
| Green Lake - B | 10021522 | Map | 2007 | Details |
| Green Lake - C | 10021523 | Map | 2007 | Details |
| Green Lake - D | 10021524 | Map | 2007 | Details |
| Green Lake - E | 10021525 | Map | 2024 | Details |
| Green Lake - East Basin | 10042257 | Map | 2015 | Details |
| Green Lake - East Basin 1 | 10051507 | Map | 2018 | Details |
| Green Lake - East Basin 2 | 10051508 | Map | 2018 | Details |
| Green Lake - East Basin 3 | 10051509 | Map | 2018 | Details |
| Green Lake - East Basin 4 | 10051510 | Map | 2018 | Details |
| Green Lake - East Basin 5 | 10051511 | Map | 2018 | Details |
| Green Lake - East End Basin - Deep Hole (USGS) | 243021 | Map | 2024 | Details |
| Green Lake - Eastern Basin (E-1) | 10041640 | Map | 1999 | Details |
| Green Lake - Eastern Basin (E-2) | 10041641 | Map | 1999 | Details |
| Green Lake - Eastern Basin (E-3) | 10041642 | Map | 1999 | Details |
| Green Lake - Eastern Basin (E-4) | 10041643 | Map | 1999 | Details |
| Green Lake - Eastern Basin (E-5) | 10041644 | Map | 1999 | Details |
| Green Lake - Eastern Basin (E-6) | 10041645 | Map | 1999 | Details |
| Green Lake - Eastern Basin (E-7) | 10041646 | Map | 1999 | Details |
| Green Lake - F | 10021526 | Map | 2007 | Details |
| Green Lake - G | 10021527 | Map | 2007 | Details |
| Green Lake - H | 10021528 | Map | 2007 | Details |
| Green Lake - I | 10021529 | Map | 2007 | Details |
| Green Lake - J | 10021530 | Map | 2007 | Details |
| Green Lake - Main Basin Northern Shore (N-1) | 10041676 | Map | 1999 | Details |
| Green Lake - Main Basin Northern Shore (N-2) | 10041677 | Map | 1999 | Details |
| Green Lake - Main Basin Northern Shore (N-3) | 10041678 | Map | 1999 | Details |
| Green Lake - Main Basin Northern Shore (N-4) | 10041679 | Map | 1999 | Details |
| Green Lake - Main Basin Northern Shore (N-5) | 10041680 | Map | 1999 | Details |
| Green Lake - Main Basin Northern Shore (N-6) | 10041681 | Map | 1999 | Details |
| Green Lake - Main Basin Northern Shore (N-7) | 10041682 | Map | 1999 | Details |
| Green Lake - Main Basin Southern Shore (S-3) | 10041659 | Map | 1999 | Details |
| Green Lake - Main Basin Southern Shore (S-4) | 10041660 | Map | 1999 | Details |
| Green Lake - Main Basin Southern Shore (S-5) | 10041661 | Map | 1999 | Details |
| Green Lake - Main Basin Southern Shore (S-8) | 10041664 | Map | 1999 | Details |
| Green Lake - Main Basin Southern Shore (S-9) | 10041665 | Map | 1999 | Details |
| Green Lake - Mid Lake | 243046 | Map | 2015 | Details |
| Green Lake - Middle Site | 10041638 | Map | 1999 | Details |
| Green Lake - Middle Site 1 | 10051505 | Map | 2018 | Details |
| Green Lake - Middle Site 2 | 10051506 | Map | 2018 | Details |
| Green Lake - Middle Site 3 | 10051526 | Map | 2018 | Details |
| Green Lake - Middle Site 4 | 10051527 | Map | 2018 | Details |
| Green Lake - North East middle site | 10041639 | Map | 1999 | Details |
| Green Lake - Norwegian Bay (B-1) | 10041666 | Map | 1999 | Details |
| Green Lake - Norwegian Bay (B-10) | 10041675 | Map | 1999 | Details |
| Green Lake - Norwegian Bay (B-2) | 10041667 | Map | 1999 | Details |
| Green Lake - Norwegian Bay (B-3) | 10041668 | Map | 1999 | Details |
| Green Lake - Norwegian Bay (B-4) | 10041669 | Map | 1999 | Details |
| Green Lake - Norwegian Bay (B-5) | 10041670 | Map | 1999 | Details |
| Green Lake - Norwegian Bay (B-6) | 10041671 | Map | 1999 | Details |
| Green Lake - Norwegian Bay (B-7) | 10041672 | Map | 1999 | Details |
| Green Lake - Norwegian Bay (B-8) | 10041673 | Map | 1999 | Details |
| Green Lake - Norwegian Bay (B-9) | 10041674 | Map | 1999 | Details |
| Green Lake - South West station | 10041636 | Map | 1999 | Details |
| Green Lake - West Basin | 10042258 | Map | 2015 | Details |
| Green Lake - West Basin - Deep Hole (USGS) | 243049 | Map | 2023 | Details |
| Green Lake - West Basin 1 | 10051499 | Map | 2018 | Details |
| Green Lake - West Basin 2 | 10051500 | Map | 2018 | Details |
| Green Lake - West Basin 3 | 10051501 | Map | 2018 | Details |
| Green Lake - West Basin 4 | 10051502 | Map | 2018 | Details |
| Green Lake - West Basin 5 | 10051503 | Map | 2018 | Details |
| Green Lake - West Basin 6 | 10051504 | Map | 2018 | Details |
| Green Lake - Western Basin (W-1) | 10041647 | Map | 1999 | Details |
| Green Lake - Western Basin (W-10) | 10041655 | Map | 1999 | Details |
| Green Lake - Western Basin (W-11) | 10041656 | Map | 1999 | Details |
| Green Lake - Western Basin (W-2) | 10041744 | Map | 1999 | Details |
| Green Lake - Western Basin (W-3) | 10041648 | Map | 1999 | Details |
| Green Lake - Western Basin (W-4) | 10041649 | Map | 1999 | Details |
| Green Lake - Western Basin (W-5) | 10041650 | Map | 1999 | Details |
| Green Lake - Western Basin (W-6) | 10041651 | Map | 1999 | Details |
| Green Lake - Western Basin (W-7) | 10041652 | Map | 1999 | Details |
| Green Lake - Western Basin (W-8) | 10041653 | Map | 1999 | Details |
| Green Lake - Western Basin (W-9) | 10041654 | Map | 1999 | Details |
| Green Lake - at CTH A (USGS 04073468) | 10021521 | Map | 2024 | Details |
| Green Lake County K Marsh | 10047854 | Map | 2019 | Details |