Mini-secchi disk

Overview

Secchi disk measurements have been used to record water transparency over hundreds of years, and are used as a proxy for eutrophication in international water quality monitoring programmes. Recently, a simple hand-held device was designed to measure the Secchi depth and water colour (Forel-Ule scale) of lake, estuarine and nearshore regions. The device is manufactured with marine resistant materials (mostly biodegradable) using a 3D printer and basic workshop tools. It is inexpensive to manufacture, lightweight, easy to use, and accessible to a wide range of users. It builds on a long tradition in optical limnology and oceanography, but is modified for ease of operation in smaller water bodies, and from small watercraft and platforms.
 
As part of ongoing development, MONOCLE has partnered with Brewtek, who designed the device, to provide further support for enhanced data flows and analysis. A new mobile App is designed to collect photos and the disk has been expanded with a clip to attach pH paper.
 
The 3D-printable design is particularly useful in community, educational and hobbyist settings.
For larger projects, mass-manufacturing is desired and this is currently being set up, with the first units expected to be available mid-2022.

What does it measure?

• Water transparency
• Colour
• pH

How does it work?

The disk is lowered from a jetty or boat. Using an integrated measurement tape on a spindle, precise readings of the maximum visibility depth of the disk can be recorded. With the disk at half the visibility depth, the user is requested to estimate water colour using the Forel-Ule scale which is attached to the spindle. Additional observations of pH and surface water colour can be recorded through the app. The disk has an ultra-compact design and easily fits in a backpack to take on excursions in nature. In windy conditions additional weight can easily be added to the disk.

• High portability
• Easy deployment and storage
• Assess water colour, transparency and pH using a single device
• Contribute to image analysis by submitting photos through mobile App

Image gallery

Deployment information

Citizen scientists can deploy from the shore or a boat.

Instructional video

Standardised data access

We provide several interoperable data interfaces, as detailed below:

Mini-secchi disk data is owned by Plymouth Marine Laboratory and DDQ and available in WMS and WFS formats:

Front-end 
WMS GetCapabilities
WFS GetCapabilities
Dashboard

Documentation and publications

Supporting materials

User guide: Deploying the mini-secchi disk (PDF 1.4MB)
Video: How to deploy a Mini-Secchi disk
Download App in the Google Play store
Download App in the Apple store

Download the operational protocols for MONOCLE sensors and platforms
This document provides a set of protocols for the deployment of MONOCLE systems to ensure best practices to collect reliable data.
System user and developer handbook

This handbook provides an overview of the data requirements and interfaces that were adopted in the sensors and observation platforms of MONOCLE.

• A Printable Device for Measuring Clarity and Colour in Lake and Nearshore Waters (research paper by Brewin et al.)
• MONOCLE sensor integration materials.
• 3D-printable designs are available under CC-BY-SA 4.0 license as supplementary materials to Brewin et al. (2019)
• Citizen Science Tools Reveal Changes in Estuarine Water Quality Following Demolition of Buildings. 2021. Remote Sensing.13(9):1683. Menon et al.
• Citizen Scientists Contribute to Real-Time Monitoring of Lake Water Quality Using 3D Printed Mini Secchi Disks. 2021. George G et al. Frontiers in Water.  
• Effect of Reduced Anthropogenic Activities on Water Quality in Lake Vembanad, India. 2021. Kulk G et al. Remote Sensing. 13(9):1631.

Sensor deployment activity

The data below shows recent sensor deployment activity. Access more detail and explore other sensor deployment activity on the MONOCLE dashboard .