Press Release – Forest and Bird Lake Clearwater in Ashburton Basin lakes is closed as of yesterday until further notice due to terrible water quality from a potentially toxic algal bloom. The algal bloom is caused by increased nitrogen and phosphorus levels in the catchment. Canterbury … Lake Clearwater in Ashburton Basin lakes is closed as of yesterday until further notice due to terrible water quality from a potentially toxic algal bloom. Land use intensification of sheep and beef farming over the past 10 years is taking a toll on biodiversity and recreation for Lake Clearwater and neighbouring lakes and wetlands. The area is normally known for wildlife like Australasian crested grebes and secretive wetland birds like bitterns, as well as recreational fishing, boating, and windsurfing.