Merseyside has a rich industrial past with continued urban influences. Despite efforts, the Lower Mersey is still failing to meet European standards in water quality. Many of its urban tributaries are heavily modified and subject to high levels of urban run-off.

The Alt and Cossens catchment contains two-thirds of farmland which is mostly used for salad and vegetable growing and the lower reaches of the catchment are reclaimed from large areas of mossland and bogs, and are now highly modified.

In contrast, the upper reaches of the Alt are very urban in nature and are possibly the main cause of pollution in the Alt and its tributaries, which is added to by the inputs from agriculture.

Both the Lower Mersey and Alt and Crossens are hosted by Mersey Rivers Trust.