The exercise will take place in and around Northumbrian Water′s underground service reservoir, at Plessey, close to Northumberlandia.
The operation will feature the removal of a "casualty" from the underground tank, and will see around 30 people on site, with a number of emergency services vehicles involved.
Ian Wade, Strategic Network Regional Manager at Northumbrian Water, said: "Exercise Blue Water will be very visible, particularly to those visiting Northumberlandia, but we want to assure people that it is a training operation that is taking place and there is no cause for concern.
"Most of the activity will take place inside the reservoir, but it will involve emergency services arriving and entering, then leaving the site, as well as what looks like a casualty, but it is all planned.
"We′re grateful to Northumberland Fire and Rescue and to the team at the North East Ambulance Service for working with us on this exercise and helping to ensure that we are able to look after our people, even in the most testing of circumstances."
While the exercise is expected to run from 10am to 2pm, it is likely that activity will be taking place on site between 8am and 4pm.
Anybody who has any concerns can contact Northumbrian Water on 0345 7171100.