The river has suffered from heavy pollution from industry and sewage upstream and run-off from farmland in its lower reaches.

The river has benefited from clean-up schemes and a de-culverting process to improve its water quality and provide a better environment for wildlife.

It then runs south of Formby and empties into the Irish Sea, near the edge of the River Mersey estuary at Hightown.

[6][7] The Alt then flows at a low gradient across an alluvium plain in a northwesterly direction before turning southwards and emptying into the River Mersey at Hightown between Crosby and Formby.

[8] The Alt's catchment boundary reaches as far as Banks and Crossens in the north and out to Burscough and Kirkby in the east.

[21] New sewage farms at Croxteth and Hillhouse plus modernisation to existing sewage farms and the decrease in heavy industry in Knowsley, Kirkby and Aintree began to clean up the river and by the early 1990s freshwater fish began to colonise the river from tributaries like Sudell Brook and Downholland Brook.

Initially tied in with a development plan connected with Stonebridge Cross, the 980-foot (300 m) section was opened to daylight to create a meandering riverside that stretched to 2,850-foot (870 m) and would help when the river was in flood as well as improve the area for wildlife.