Over the past several years serious pollution incidents have been falling, largely because of our regulation.

The agency said this weekend that the overflows with deemed consents were not considered to be causing serious pollution, but new restrictions would be imposed on them.

Often thieves leave the pump nozzle open, so that diesel runs away on to the ground leading to serious pollution.

The industrial development of the lower banks led to serious pollution of the creek in the 20th century.

These and the sewage works outfalls are generally well-regulated, but there have been some serious pollution incidents as a result of poor agricultural practice.