Wandsworth park lakes provide high amenity value in the borough and provide exceptional habitat for wetland flora and fauna, thus also making them important for conservation.

However, over time their quality deteriorated due to changes in management, and by 1992 the lakes were suffering from eutrophication and the aquatic environment and its surrounds became impoverished. Improving and maintaining the quality of these lakes for both amenity and wildlife can only be brought about by gaining a thorough understanding of the chemistry and biology of the sites. By understanding the ecological functions of a lake, factors such as water supply, fish stocking, marginal and submerged macrophyte planting and aeration can be effectively directed to maximise the conservation and aesthetic value of the lakes

Objectives

Extensive restoration measures were carried out in 1993. In 1997, ENSIS Ltd. was commissioned to continue post-restoration monitoring of six lakes; Main Lake and Ladies Pool (Battersea Park), Wildlife Lake and Three Island Pond (Wandsworth Common), Tooting Common Lake and King George's Park Lake. This project represented a continuation of the monitoring programme and, based on the results, has provided a series of management recommendations for the Borough Council.

Methods

Quarterly monitoring was undertaken at the six lakes for the following:

  • Water quality - including total and soluble reactive phosphorus, nitrate, chlorophyll a, dissolved oxygen and biochemical oxygen demand (BOD)
  • Phytoplankton - focusing on nuisance species and those that present potential health risks such as cyanobacteria
  • Zooplankton
  • Aquatic invertebrates
  • Aquatic macrophytes - full vegetation surveys conducted

Results:

Water quality monitoring and biological data were reported quarterly. They indicated poor water quality, in particular high nutrient concentrations, low oxygen levels and high BOD) and high concentrations of cyanobacteria

Recommendations:

A brief interpretation report was provided detailing specific priority areas for management, and highlighting medium and long-term actions to improve water quality and enhance the ecological function of the sites. For each site, specific recommendations were made for annual planting of aquatic and marginal vegetation and where applicable, for the manipulation of fish stocks.

  • Where sites rely on run-off from the surrounding parks and urban areas, or are topped up by mains tap water, water quality will be poor. Run-off brings with it sediment and nutrients from the parkland, and mains water, although fine for drinking, is high in plant nutrients (mainly nitrogen and phosphorus) which in lakes, encourages the growth of planktonic algae and blanketweed which are detrimental to the ecological function of the lakes. It was recommended that water inflow should be sourced from a borehole supply (Battersea and King George‚Äôs Park Lakes) to improve water quality. The boreholes bring water from aquifers deep below the surface which are less likely to be impacted by nutrient pollution.
  • For those sites where conditions were suitable (i.e. water quality and fish populations) a programme of planting aquatic plants was recommended. This covered when to plant, what to plant, planting density, planting methods and protection. It was strongly recommended that no non-native species were planted and that efforts should be made to ensure all stock plants are free from contamination from non-native species.
  • While recognising that it is unlikely that carp can be removed from Battersea Park Lake, it was recommended that stocking densities should be lowered during the planting phase in an effort to facilitate the growth of plants. A low density (absence) of carp is to be encouraged with a focus on native fish species. Stocking of perch and pike which will help to reduce fry numbers and maintain a more balanced fishery was also recommended. Working together with angling groups to promote native fisheries may be necessary if fish stocks are to be manipulated away from a dominance by carp. If fish populations can be effectively managed in this way water quality should also improve, at least in terms of clarity.
  • Links:

    Wandsworth Habitats: Lakes and Ponds

River Mun Restoration
Wandsworth Park Lake © Ben Goldsmith