ToolboxField ToolsSecchi disk

A woman kneeling at the lake shoreline collecting water samples into test tubes

Field Tools

Secchi disk

Name: Secchi disk
Brand: Lake Pulse
Price: 50.00 USD
Availability: InStock

The oldest measurement in limnology, and still one of the most useful.

$50

Checkout arrives with the store connection. Orders attach to the lake on your account.

Overview

A black-and-white disk lowered into the water until it disappears from view. The depth at which that happens is the Secchi depth, and it is a direct measure of water transparency — the presence of algae, suspended particles, and sediment.

Simple, immediate, requiring no power, calibration, or expertise.

What's measured & how

1 parameter

What's measured & how for Secchi disk
Parameter	Unit	Measured by
Water clarity (Secchi depth)	ft / m	You

Water clarity (Secchi depth)
Unit:
ft / m
Measured by:
You

You get

Your readings, dated and mapped, on your lake's timeline

How it's produced

Instrument: Weighted Secchi disk on a marked line
Method: Standard Secchi depth reading, shaded side of the boat or dock
Logged in: Lake Pulse app or Portal

Product category

Physical ProductShips to you

Availability
Shipping
Flat-rate to your front door. Shipping details
SKU
LP-FS-001

Example result

8.5 ft

Clearer than your 3-year average for July

Turnaround

Ships to your address within 3–5 business days of ordering.

What problem does this solve for our lake?

A Secchi disk costs $50 and produces the longest-running, most comparable dataset a lake can own. Records going back to the 1970s exist in ordinary lake communities, and they are frequently the most valuable environmental data those communities hold.
The reason is standardisation. The method has not changed in a century and a half, requires no instrument that can drift out of calibration, and produces a number that means the same thing whoever collected it. A reading taken by a volunteer in 1981 is directly comparable to one taken this morning — which is true of almost nothing else in lake monitoring.
Transparency itself is a real indicator, not just a proxy. It tracks algal abundance closely enough to be a first-order productivity measurement, and a declining multi-year Secchi trend is one of the clearest signals of eutrophication available.
Every serious volunteer monitoring programme in the country is built on this disk. If your lake measures one thing, measure this.

What's included?

Secchi disk with measured line
Standard black-and-white quartered pattern
Ready to use — no calibration, power, or setup
Compatible with every historical Secchi record ever collected

What's not included

Water chemistry of any kind. Transparency indicates productivity; it does not measure nutrients.
Identification of what is reducing clarity — algae, sediment, or tannins all reduce Secchi depth differently
A boat, which you will need to reach open water
Automated or logged readings

Requirements

A boat or dock over water deeper than the expected Secchi depth
The same site, revisited — comparability is the entire value
Consistent conditions: mid-morning to mid-afternoon, shaded side of the boat, no sunglasses
Someone willing to take a reading every week or two through the season

What you get back

Results

A direct transparency measurement, comparable to every Secchi reading ever taken anywhere
A seasonal clarity curve, and over years the trend that indicates whether your lake is changing
The backbone dataset for volunteer monitoring, grant applications, and long-term records
Results load into your lake's Data Library in the Lake Pulse Portal
Data can be charted in the Analytics Hub, used to trigger alerts, or shared across your lake community
Results are found in your lake's portal, accessible only to Plus, Lake Admin, and PRO subscription tiers

Pro tips

No sunglasses, shaded side of the boat, between 10am and 2pm. Deviating from these is how a record becomes uncomparable.
Same site, same person where possible. Between-observer variation is real but small; between-site variation is enormous.
Every week or two, all season. Frequency beats precision here by a wide margin.
Log it in the portal, not a notebook. The notebook leaves when the volunteer does — which is how most lakes lost their 1990s records.
Chase down your lake's old readings. Somebody has them, and thirty years of Secchi data is worth more than anything you can buy new.
A sudden drop means something. Slow decline is eutrophication; an abrupt change is an event worth sampling for.

Results sync to the Portal for Plus, Lake Admin, and PRO subscribers

Results from this product land in your lake's shared record in the Portal — next to everything else your lake has ever measured, instead of in an inbox.

Compare subscriptions

About these results

Every reading and observation shows the date it was collected. Field values are made by you or your members, at the place and time recorded, and depend on the instrument, the observer, light, weather, and technique. They are not laboratory analyses. Observations, such as Lake Tag presses or microscope sightings, are reports, not verified identifications. Lake Pulse records what is submitted; it does not independently verify each entry. Results can help you make decisions about safe swimming and water use, but no result is definitive for every place and time. It is always good practice to check posted signs and your state or local health authorities.

Questions on this?

Our team can help you choose the right solution for your lake, explain how results sync to your Portal, or point you to the right subscription.

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