Yorkshire Water released untreated sewage into rivers and the sea for more than a quarter of a million hours in 2025, new figures reveal.
However, the 285,000 hours of discharge represented a fall of 33% on the previous year's total of 430,000.
Last year, which included the driest spring for 132 years leading to a hosepipe ban from July to December, saw the number of spills fall from from 88,164 to 51,404, according to the firm's records.
Yorkshire Water said the reduction was a result of big investments but clean river campaigners said the figures were still too high and partly a result of less rainfall.
Water companies are legally allowed to release untreated sewage into rivers and seas after heavy rain so that the pipe network doesn't become overwhelmed and back-up into people's homes.
Yorkshire Water said that by April 2030 it will have spent £1.5bn on improvements to 450 storm overflows.
Customers are paying more through higher bills to help fund the modernisation.
Hundreds of underground tanks are being built that can store up to 300,000 litres of waste water to prevent it entering water courses after heavy rainfall.
The government has set a target for each storm overflow, also known as a Combined Sewer Overflow (CSO), to operate on no more than 10 occasions annually.
Many in Yorkshire currently operate about 40 times a year.
Jon Stokes, from Yorkshire Water, said: "The tanks are sized so that we can make sure they don't spill more than 10 times a year, that will have a very minimal impact on water quality, there will be a mixture of run-off from roads and roofs, mixed with the foul sewage from people homes."
Yorkshire Water said that reducing the number of spills below 10 would involve billions of pounds additional funding and a complete re-plumbing of the sewer network.
Campaigners who want to see cleaner rivers said that they would like to see all waste water treated before it was released.
Adrian Sturdy, from the River Nidd Action Group in Knaresborough, said wet wipes were caught up in low-hanging trees above the river after a storm overflow pipe operated.
He said: "Baby wipes shouldn't be flushed down toilets, but they are evidence that there is sewage coming into our river and whenever there's a storm Yorkshire Water are releasing it into our rivers.
"It's terrible we come and clean up the wipes and then three months later we've got baby wipes six foot up a tree; the sewage shouldn't really go into the river at all."
Yorkshire Water said that, as part of the investment, all storm overflow sites would have screens installed to prevent wet wipes and other solids entering rivers.
Work carried out by Yorkshire Water in 2025 included the building of a £2.4m storage tank at Cudworth near Barnsley that has resulted in discharge from one the CSO falling from 41 incidents in 2021 to zero in 2025.
The firm also said that investment at Whitby Esplanade CSO resulted in a 75% reduction in discharges.