Although infequent, the influx of endosulfan into rivers during a runoff event can pose a major threat of acute contamination. Preece and Whalley (1993) monitored endosulfan concentrations in surface waters in the Gwydir River during a storm event in December 1991 in which total endosulfan concentrations peaked at around 7 ug/L and elevated endosulfan concentrations persisted for several days.  Muschal (1997) also sampled endosulfan concentrations in the Gwydir River during a storm event in January 1997 during which total endosulfan concentrations reached 1.75ug/L and elevated endosulfan concentrations persisted for at least 48 hours. As the ANZECC (1992) guideline for the protection of aquatic ecosystems is 0.01ug/L, and the revised (ANZECC and ARMCANZ 2000) is 0.03ug/L, storm events such as these pose a major threat to riverine ecosystems.

(The Transport, Fate and Effects of Endosulfan in the Australian Freshwater Environment. (Grant C Hose, Richard P Lim and Ross P Vine). Australasian Journal of Ecotoxicology Vol 9 pp101-111, 2003