The last couple of weeks we have been busy to test the equipment to measure the amount of litter in the Meuse. There are some elements worth mentioning:
The ship de Blauwe Reiger (The Blue Heron) is a 14.95 mtr long “barkas” build in 1952 in Germany as a service vessel for all kinds of jobs. The skipper (Twan) rescued her from a scrapyard and rebuilt her almost in her original state as a basic recreational vessel. The present owners (Yamila and Hergat) keep Twan using and servicing the boat and go out frequently together just for the pleasure of sailing on the Meuse.
When they heard of our interest in using the Blauwe Reiger for measuring purposes, they immediately agreed to cooperate and they are ever more enthusiastic about the purpose of this whole venture. No other boat owner would allow us to drill holes in the hull or install masts and gear on their ships, but they do… and we cannot be grateful enough for their cooperation!
The catamaran shaped pontoon, carrying the net between the floatation bodies was designed to be towed alongside the boat to prevent measuring in disturbed water from the propellor. As the tests showed, the floatation bodies and the shape they have, just leave the water flowing between them almost undisturbed and the net can cleanly cut through a surface of 1m x 0.5 m water. After the first test this was not yet perfect, but after modification it worked out beautifully. The net operates at a depth of approx. 10 cm. and catches the materials which are in suspension. As a hypothesis we assume this 10 – 60 cm depth will be representative for the rest of the water column, especially in turbulent conditions, but this has to be proven.
The pontoon can be equipped with a net skimming the surface to catch the materials that really float on the surface like bottles, branches and other products with a low specific surface (surface/volume ratio).