Lake Cavanaugh Water Quality Testing Program

The Lake Cavanaugh Improvement Association sponsors periodic water quality testing of Lake Cavanaugh. By becoming a member of LCIA, you help support this testing and can also gain access to view this data. The following water quality attributes are measured, typically monthly from May to September each year:

1. Temperature thermocline gradient from 0-22 meters
2. Dissolved Oxygen at 3 and 17 meters
3. pH at 3 and 17 meters
4. Visibility depth
5. Fecal coliform at 6-8 points along the shoreline

View Water Quality Data

Please CLICK HERE to view historical water quality data dating back to 2015.

• You must be an LCIA member to obtain access
• If you are a member, please use the login that was provided to you earlier in the year
• Not a member? Consider joining the LCIA today. Your membership helps us continue to monitor the lakes health

About the Lake and Our Testing

Why we chose these depths to test

Lake Cavanaugh has a maximum depth of 80 feet, with a large portion of the lake at around 40-60 feet. The top layer of the lake (from 0-20’) is where water interacts with air and becomes saturated with Oxygen. The lowest layer of the thermocline in Lake Cavanaugh is from 40-80’ (Hypolimnion) and receives oxygen from the top layer via mixing and turnover through the middle thermocline layer (20-40’). This is an important process that keeps Oxygen levels in deeper colder waters habitable for fish and other aquatic species. The LCIA monitors the dissolved oxygen and pH at the deep layer (56’) and shallow surface layer (20’) to ensure the lake is continuing to maintain healthy conditions.

How we Test

We use the following methods for testing:

1. Dissolved Oxygen (DO) & pH Levels:
• We use a Optical DO and pH probes to take measurements of water captured at various depths
• We perform DO and pH manual titrations periodically as well
2. Temperature:
• We use a Thermocouple probe that measures temperature every meter from 0-22 meter depths
3. Visibility:
• We use a Secchi disk to test visibility
4. Bacterial Coliform Testing:
• We implemented the Millipore fecal coliform testing procedure in partnership with the Padilla Bay Research Institute Stream Team, to perform this microbial testing on-site at Lake Cavanaugh

What is Lake Turnover & Why Does it Happen?

The temperature of the top layer of water is influenced by the air temperature. When the top layer of water reaches 39.2F (4C), water has it’s maximum density and it falls to the bottom, causing mixing of upper/lower layers across the thermocline. This happens when it warms up past 4C in the spring, and cools down below 4C in the fall/winter.

What you can do to keep Lake Cavanaugh Clean

There are many things that impact the water quality at Lake Cavanaugh. The three major ones are:

Excess Phosphorous & Nitrogen from Fertilizers & Soaps

When people put fertilizer on their lawns near the waterfront, or soaps on their decks, patios or roofs, it does not stay where you put it. We have all seen the floods of rain that streams down straight into the lake from our gutters and lawns. The Phosphorous and Nitrogen get carried into the lake and cause an increase in algae and plant growth. This contributes to algae blooms, reduced visibility, and reduced oxygenation in the lower layers of the lake. Phosphorous is of particular concern because there is no easy way to remove it from lakes, and it is typically the rate limiting nutrient for algae blooms. Removing it usually involves soaking it up by applying chemical particles that absorb it and then the particles settle to the sediment layer and remains there for very long periods. Lake Cavanaugh has never needed a chemical treatment like this to remove phosphorous, but many other more populated lakes in the area have. Let’s all be diligent and ensure we don’t ever get to that point. Please do your part and prevent excess phosphorous in Lake Cavanaugh!

Pesticides & Insecticide Contaminations

Most people hate dealing with spiders and bugs on their decks, lawns and docks. But please be careful what you use to manage them. Most pesticides and insecticides are toxic to fish, and some are also toxic to humans. Bifenthrin is a popular one that many pest control companies use, but this can be toxic to fish. It should never be used around the water. Many fertilizers even contain this, and it washes right into the lake. Please make sure you read labels and if it says it’s safe “when dry”, don’t trust it. Do your own research and make sure it’s safe around fish and kids and pets regardless of whether it remains wet. Conditions around Lake Cavanaugh can sometimes cause these products to remain wet and transferrable to kids, pets, or runoff into the lake for extended periods of time. Some of these products even contain PFOAs (forever chemicals) that don’t break down for decades or longer and can accumulate to toxic levels that are harmful to both fish and humans.

There are many natural alternative pest products out there. Parker Eco Pest Control is one company that uses eco-safe products like Essentria around properties at Lake Cavanaugh. Please keep our lake free of toxic pesticides and forever chemicals!

Bacterial Growth on the Shoreline

Bacteria can grow anywhere given the right conditions. When the water warms up or there are pockets of algae growth that cause local increases in temperature along the shore, there can become concentrated areas of bacterial growth in the event there is a contamination source. Especially in the summer when surface temps can reach the high 70’s. Typical bacterial contamination sources are: large flocks of water foul or pet waste on the beaches, faulty septic systems, and stormwater runoff. We have never seen toxic or even remotely concerning levels of bacterial coliforms at Lake Cavanaugh in the past, but we continue to test monthly to ensure the lake is remaining clean and safe. Please help prevent bacterial growth by having your septic tank inspected regularly and keeping pets from defecating on the beaches.