Wellington Dam is the largest dam in the South West and the second largest in Western Australia,and is fed by the Collie River. Wellington Dam was built in the early 1900s to supply water to the Great Southern Towns Water Supply system— the pipeline system that supplies water to the wheatbelt towns in Southern WA. Supplying towns as far North as Northam, East to Lake Grace, South to Katanning. The line basically runs parallel to the Goldfields water supply scheme (from Mundaring Weir to Kalgoorlie) and the two lines even join at one point. It gets its water from the Collie River catchment, which started going salty during the 1960s and 1970s. Much re-afforestation work has been happening since the 1980s to slow down the trend of rising salinity. A new dam on nearby Harris River was commissioned in the 1990s to supply fresh water until such time as Wellington Dam is fresh again.