“From 2011 until July 2016, only one sample tested for pesticides has returned a result above the level of detection of the test method. The measured value, 0.0015 mg/L for Dicamba at Darwin is still well below the 2011 ADWG limit of 0.1 mg/L.
Occasionally weed problems in reservoirs and catchments can only be managed effectively through the use of herbicides. Dicamba (Banvel, 3, 6-dichloro-2-methoxybenzoic acid) is a moderate to low toxicity herbicide used to control weeds and mimosa in the catchment of Darwin River Reservoir.
Dicamba is moderately persistent in soil and breaks down to very simple substances such as carbon dioxide and water. The reported half life of Dicamba in soil ranges from one to six weeks. This herbicide is applied two to three times a year as part of the mimosa control program.
Although monitored for several years, pesticides have rarely been detected in the Northern Territory water supplies despite limited use in some areas. In consideration of these results,
pesticide monitoring during 2011-16 was restricted to Darwin and Katherine water supplies. These supplies are considered potentially vulnerable to pesticide contamination due to agricultural activities close to production bores and surface water sources.”
Power and Water Corporation – Water Quality Report 2016