The short answer is that it stands for Diver-Assisted Suction Harvesting. The long answer is that it is the best way in most cases to get rid of unwanted aquatic vegetation, including invasive species.
There are other ways of addressing unwanted vegetation, such as aquatic herbicides, dredging, use of dyes that will temporarily suppress photosynthesis (thus killing weeds), and the use of shade to suppress weed growth. All of these other methods have significant problems, many stemming from the lack of specificity of the treatment.
Dredging
Dredging requires bringing heavy equipment to bear on the problem. It removes desirable and undesirable plants altogether, and disturbs the marine environment. Bringing heavy equipment to the shoreline also damages plants at the water/land boundary, and increases the potential for erosion as a result of disturbing barrier plants that keep soil in place. Dredging also requires permits.
Aquatic Herbicides
Aquatic herbicides tend to kill desirable aquatic species which are necessary to the proper functioning of the aquatic ecosystem along with the undesirable ones. Aquatic plants are essential to providing food, cover and oxygen to aquatic animals, such as fish. When aquatic plants are killed off en mass and not removed from the environment, their decomposition removes oxygen from the water, which can stress and kill animal life, many aquatic herbicides can be toxic to land plants and to some extent also to animals.
Dyes
Though they are less toxic than aquatic herbicides, dyes suffer from some of the same problems of lack of specificity, killing desirable aquatic plant species as well as the undesirable ones.
Shade
Is difficult to manage on larger bodies of water, and may reduce the usefulness of shore areas for activities such as swimming. Shade can also affect the spawning of fish and other aquatic animals by reducing temperatures in the shallows.
D.A.S.H. Is More Specific
In contrast with the above methods, Diver-Assisted Suction Harvesting is targeted at the species that cause problems, and not at those that contribute to a properly functioning aquatic ecosystem. Divers determine which weeds to feed into powerful suction motors that force them to the surface, where they are separated using mesh. Small animals are passed harmlessly through, and returned along with the water to the lake or pond. Trained divers are also able to remove the root systems, and the removed material is then converted into compost, also removing some of the leached-in phosphates that have likely contributed to the spread of unwanted vegetation in the first place. Over two or three years treatment, unwanted weeds are suppressed thoroughly enough that it they are slow to re-establish themselves, so that additional D.A.S.H. treatments become less necessary from year to year.
D.A.S.H. Is More Environmentally Sound
D.A.S.H. doesn’t require dredging permits, because any removal of lake bed is entirely incidental and is kept to a minimum. It’s easy to understand how targeted removal of aquatic vegetation is less disruptive to aquatic life than the other methods typically employed.
D.A.S.H. Is More Effective In the Long-Term
After several treatments, unwanted species are suppressed to the extent that they are more easily controlled, which means that treatments no longer need to be annual.
For information on how their D.A.S.H. treatments can help you get your weed problem under control, call the experts at Eco Waterway, serving Wisconsin and Illinois with a proven record of effectiveness.