Wascana Creek, which meanders through Regina, will receive some partially treated waste water from the city for about a week. (CBC)

Regina's waste water treatment system has been inundated with so much rain that some partially treated sewage, mixed with fully treated waste water, will be released into Wascana Creek, the city announced Thursday.

The rain issue is affecting lagoons that hold waste water as part of the treatment system. The holding lagoons are full to the brim and, to make room, the city will release some waste water before it has been thoroughly treated.

The mix will be about 20 per cent partially treated with 80 per cent fully treated.

The partially treated portion will have skipped the system's phosphorous removal stage.

Having too much phosphorous in a natural water body can affect the balance of oxygen in the water and lead to problematic algae growth.

The city said it has been in touch with the provincial regulator, the Water Security Agency, about the effluent discharge which is expected to last about one week.

"The city expects to continue meeting all permit requirements," an official statement from the city said.