Penrith Lakes Scheme is concerned with the rehabilitation of gravel pits to create a system of large recreational lakes. A potential submerged macrophyte problem has been identified in an existing man-made lake.

The need to control the macrophytes is dependent on the proposed end use of the lakes and the potential area of invasion.

A variety of control options were assessed. Plastic blankets were tested to determine their effectiveness in controlling macrophyte growth specifically in swimming and boat access areas. Comparisons of clear, black and black woven blankets were conducted. Experiments revealed that 90% of the plants under the black and black woven blankets died within six weeks. Under clear blankets plants were reduced by between 20%-90%.

Analysis showed that significant interactions occurred between sites and treatments and times, from which it can be inferred that none are independent of each other. Success in the reduction of macrophytes appears dependent on such factors as plant species, sediment accumulation and light reduction.