Summertime...and the Problem is Algae

Algae can spurt into growth when nutrient-rich UK tap water is used to top up ponds. So in the hot dry summer months the best course of action is to wait for the rain and, if possible, prepare for dry spells by collecting as much rainwater as possible.

In hot, dry weather water evaporates from the surface of ponds and other wetlands. As the water level goes down, nutrients and pollutants are concentrated in the remaining water. Although nutrients help the flowers to grow in your garden and farms to yield big crops, they can trigger unwanted extra-vigorous growth in waterways which stifles the rest of the underwater life.

Tap water in the UK is treated to a high standard so it is safe to drink but often it still contains high levels of nutrients. These nutrients come from fertilizer washed off fields into our waterways, from domestic detergents and from run-off from hard surfaces like roads. Tap water also contains chlorine, added as a disinfectant. Although it looks clear and pure, tap water is not friendly to wildlife in ponds. Adding it when a pond is low can raise nutrient levels and the first things to take hold are often green algae such as blanket weed. A quarter of pond owners so far responding to the survey experiences trouble with this.

The best course of action is to let the water level fluctuate naturally with the weather. Many wetland animals and plants actually like this variation. If you dig a deeper area when you build a pond most aquatic wildlife will have a refuge when the water level drops.

If it is necessary to top up a pond, make the most of rainwater to keep it healthy. There are clear financial benefits to rainwater harvesting which are especially visible if you are on a water meter. Yet results show just one in 10 respondents collect all the rainwater from their roofs. Besides wasting all that valuable rainwater, they're missing out on the chance to reduce their water bills with a wastewater abatement (worth GBP20-40 depending on the water authority). Rainwater harvesting can also save money on metered bills by providing up to 70% of non-drinking water for a household. The less drinking water we use for things like ponds, plants, car washing, and even toilet flushing, the more energy efficient and planet-friendly we will all be.

As part of Wetlands in my backyard, an initiative to maximise the benefit people and wildlife in the UK get from ponds and small wetlands, WWT is running a nationwide survey which runs throughout the summer. The survey will give an insight into how people use water in their gardens, whether for wildlife, for plants, for garden appearance or for sustainability. Fll in the survey.

WWT supports the Blueprint for Water which sets out 10 steps the government must take to sort out water by 2015.