Heavy rains have hampered attempts to assess Paris' fitness for swimmers to race in the River Seine during the Summer Olympics next year, but Games officials insist the waterway will be improved in 2024.

The Open Water Swimming World Cup event has been postponed for at least 24 hours due to poor water quality caused by many days of rain, officials announced on Friday. As a result, the women's race has been moved from Saturday to Sunday, when a men's race is also scheduled.

"The water quality in the river Seine is still below acceptable standards for safeguarding swimmers' health, following several days of rainfall," the French Swimming Federation (FFN) said in a statement. "As a result, the decision has been taken, in consultation with public health authorities and event delivery partners, to modify the proposed schedule."

Earlier Friday, organizers canceled a planned training session for swimmers aiming to compete this weekend in the river that cuts through Paris after swimming's international governing body also said the water quality was below acceptable standards.

That can happen when rains cause overflows of untreated waste into the Seine. France's capital city is spending massively on water-management projects that officials say will make pollution caused by storms less frequent.

The open competition is among a raft of events being used to test Paris' Olympic plans. The Seine is the venue for marathon swimming at the Games next summer and the swimming leg of Olympic and Paralympic triathlon.

Games organizers said in a statement Friday that water quality will be improved next year when additional infrastructure to manage rains and wastewater better comes online. Those public works include a giant underground reservoir in Paris that will stock excess water during storms, so it doesn't have to be spilled untreated into the river and can be treated later.

They also say the schedule for Olympic events in the river can be adjusted next year if the water quality doesn't allow them to take place on their original dates.

Their statement said the recent weather that pushed the Seine below acceptable levels was "exceptional," with the Paris region seeing its heaviest summer rainfalls in 20 years.