+ Clarity tube

Water clarity tube measure of turbidity and suspended solids.

One of the most noticeable characteristics of an increase in turbidity or suspended solids is a decrease in water clarity. There are several methods for testing water clarity, some of these methods are very accurate but very costly and are thus not a practical option for projects that require multiple samples where pinpoint accuracy is not required.

There are three common alternatives to the time consuming and expensive methods for testing turbidity and suspended solids; these are the Secchi Disk, the Black Disk and the Transparency or Clarity Tube methods.

The Secchi Disk method is not suitable for shallow or rapidly moving water making it impractical for most South African rivers.

The Black Disk method is not suitable in rivers where aquatic plants and weeds disrupt line of sight or in shallow streams where the substrate is soft, as the movement of the apparatus often kicks up excess sediment increasing turbidity.

The clarity tube is not limited by either of the constraints experienced by the other two methods making it ideal for South African rivers. Studies done in California on the use of the clarity tube in water quality measurements, found that the clarity tube measurements showed a strong relationship to turbidity and total suspended solids.

The Clarity Tube is an inexpensive, robust and easily transported tool, which is easy to use. Several studies commend the reliability, ease and rapidity in using the clarity tube. It is recommended for use by farmers, school groups, citizen monitoring groups and local government agencies. The South African River health program has been utilising the clarity tube as an inexpensive low technology solution to managing water clarity in the absence of an expensive turbidity meter.

Clarity Tubes are developed and manufactured by GroundTruth. To place an order or to find out more about the GroundTruth Clarity Tube contact us at info@groundtruth.co.za

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+ SASS5 field equipment

Nets designed for use with the South African Scoring System SASS5

The method described for version 5 of the South African Scoring System (SASS5) requires a net with particular specifications. Namely, a soft 1mm mesh net on a 30cm square frame with stout handle.

GroundTruth produces a net with a 30cm square aluminum frame and a 135cm aluminum handle. The design of the net has been constantly refined through use in the field by GroundTruth, and the product which has now been developed is light, durable, robust and easy to maintain. The light weight of the sample nets makes them easy to wield when covering long distances on foot or when working your way through dense riparian vegetation.

Complete SASS kit

The basic SASS kit developed and refined by GroundTruth facilitates effective sample collection and manipulation in accordance with the SASS methodology, and includes the following:

  • SASS net
  • SASS tray
  • Loupe /magnifying lense
  • Tweezers and pipette
  • Additional items which can be added to the basic SASS kit include:

  • Waders
  • Life jacket
  • SASS identification guide - Aquatic Invertebrates of South African Rivers
  • The following publications by the Department of Water Affairs form useful references when undertaking SASS5 aquatic invertebrate biomonitoring:

  • Aquatic Invertebrates of South African Rivers: Illustrations. Version 2 April 2002. Institute for Water Quality Studies, Department of Water Affairs and Forestry.
  • Aquatic Invertebrates of South African Rivers: Field Guide. First Edition February 2002. Resource Quality Services, Department of Water Affairs and Forestry.
  • Both publications are currently out of print pending revised editions. In the interim GroundTruth are able to supply high quality, laminated copies of the Aquatic Invertebrates of South African Rivers: Illustrations.


    + miniSASS field kit

    GroundTruth supply miniSASS field equipment as individual items or as a kit. The following items can be supplied:

  • miniSASS net - A cost effective but robust version of the SASS5 net developed and tested by GroundTruth.
  • miniSASS tray
  • Loupe/magnifying glass
  • Tweezers and pipette
  • Assortment of sample bottles
  • + The Transparent Velocity Head Rod (TVHR)

    The TVHR is a very simple tool that allows us to measure the velocity of a stream. The TVHR is a simple construction of transparent plastic and hardwood meter sticks.

    It allows simultaneous measurement of upstream super elevated water and depressed downstream water elevation created when the rod is placed into flowing water. The difference between these water height measurements can be used to predict the depth-averaged flow velocity.

    In a field environment the TVHR is solid, lightweight, and simple enough to allow velocity measurements to be made effectively on site. It has a good accuracy; it is typically precise within 5%.

    It is 1.1 meter high and 10 cm wide, the thickness is 7 mm with a reinforcement bar at the back. The top of the tool has a handle to hold it during measurements. A lanyard has been attached to the handle to prevent the user from losing the TVHR in the river.