Chief Irrigation Officer January 1982: Fish kill Hopetoun No 1 Reservoir during October/November 1981 – probably DDT/Endosulfan. “The enquiries indicated a high probability of the fish deaths being caused by insecticides endosulphan and DDT. These chemicals were sprayed from the air by contractos during October to control grubs (Heliothus) in crops such as peas, lupins, sunflowers and tomatoes, and also to control pea weevil. As crops are sometimes as close as five metres to water supply channels, contamination of the water is very likely…There was more aerial spraying than usual in 1981…”

https://baddevelopers.nfshost.com/Docs/foewaterreport.htm#Grampians

State Rivers and Water Supply Commission

Irrigation Services Division

4 February 1982

Effect of Aerial Spraying on Water Quality

The recent fish deaths in Hopetoun No.1 reservoir have highlighted the possibility of aerial spraying resulting in contamination of water supplies. Further, in discussion with ***, it is apparent that there have been other instances in which aerial spraying is thought to have caused fish deaths.

These events are only part of the present aerial spraying scene. I am aware of a number of enquiries about the possible risks to human health from aerial spraying, and also objections raised by people who have suffered discomfort through contact with spray drift. Although these cases are considered by the Pesticide Review Committee, they are usually attended to by the Health Commission.

Two officers of the Department of Agriculture, both of whom have considerable experience with pesticides, have expressed some concern with the standard of aerial spraying. In addition, the Pesticides Review Committee is in the process of writing to the Director-General of Agriculture to determine what action is necessary to reduce the undesirable features of aerial spraying.

It seems appropriate, therefore, that an assessment be made of the effect of aerial spraying on water quality. What is required is consultation with departmental officers and others with some knowledge of aerial spraying, field observations of aerial spraying near water supplies, and details of fish deaths or other evidence of water contamination as a result of aerial spraying.