Dealing with Weed

Advice with dealing with large growths of aquatic weed on inland lakes, gravel pits, reservoirs and rivers which can cause problems for racing and recreational boating in the summer months.

The prolific growth of weed has been an increasing issue for many boaters. The prolific growth of aquatic plants may force clubs to operate in a restricted area, or not at all, and in some cases to cancel events.

Inland lakes, gravel pits, reservoirs and rivers can be affected by large growths of aquatic plants which can cause problems for boating in the summer months. Although boaters would regard these as weeds, other people may regard them as valuable for their contribution in other ways. There is a great variety of plants growing in different habitats that can cause problems and often several possible management solutions.

There are often calls for immediate action to reduce problems, but such actions are not always feasible. Herbicide applications used in the past are now mostly banned. Analysis of the cause of the problem and a search for a sustainable long-term solution is what is required. There may be other bodies that you could involve who share your concerns. Inland lakes, gravel pits, reservoirs and rivers can sometimes be affected by large growths of aquatic weed which can cause problems for racing and recreational boating over the sailing season.

Local water conditions control the growth of pond weed. Factors include water temperature, acidity/alkalinity, level of nutrients, turbidity and sunshine hours/strength. Although many of these factors will be out of your control, it is worth considering whether your waterbody has a high nutrient input coming from a source nearby and whether there is anything which can be done to reduce this input. Broadly speaking, excessive nutrients most often come from point sources such as sewage effluents or diffuse sources such as the run-off from agricultural or pastoral land.

What are the options?

Although a few management options are available to clubs faced with weed problems, management is often required on an ongoing basis over the season. The RYA has produced guidance that provides an overview of the most common methods of weed management along with case studies to illustrate successful approaches.

There is no single solution which is right for every club. Cutting can be time-consuming and costly, especially where special disposal of the cut weed is required, but it does mean the water is ready for sailing on as soon as the cutting has been completed. On the other hand, regularly treating the water with dye can be both a cheaper and less time-intensive solution which, under the right conditions, can keep rooted weeds under control all season. However, dye only works if used early before the weed is well established and it will not have any effect on free-floating weed at the surface. Dye may not be permitted for use if your waterbody is protected for conservation, if it is not a "closed system" or in some cases if it is used as a drinking water reservoir.

In addition to the most common weed management options - cutting, harrowing and dye use - there are many options which have proved successful in water bodies plagued by excessive weed growth. These include options such as planting reeds around the edge of the waterbody and using weighted-down jute matting to cover the waterbody bed in order to prevent growth.

Whatever option your club decides on, make sure that you seek permission from the land owner and get any permission or consents which may be necessary (e.g. from Natural England or the Environment Agency) in advance of any works. If you are in tidal or coastal waters you will also need to seek advice from the Marine Management Organisation in case a marine licence is required.

If your waters are protected for conservation, you may find that some of your management options are limited due to the effect they may have on the protected species. If you experience difficulty with this, please contact the RYA at or on 02380 604 223.

Pooling resources

If your club is suffering from weed problems then it might be worth checking to see if any other clubs in your area are in the same predicament. Not only could you learn from each other’s experiences there is a possibility that you may find that combining resources opens up the range of management options available to you such as being able to buy a dedicated weed-cutting boat to share.

If dealing with weed is a new issue for your club then have a look at the RYA weed guidance. If you are struggling to gain consent to manage the weed from Natural England or your land owner, please contact the Planning and Sustainability team at the RYA or your Regional Development Officer (RDO).

Please also get in touch if your club is an old hand at dealing with weed and is successfully managing the issue! We would like to learn from your experiences and add to our knowledge base.