CANBERRA, Australia (AP) _ Rising salt levels along Australia greatest river system are undermining country roads, eating into house foundations and laying waste to large strips of farmland, according to a report published Friday.

The problem is so bad that if it continues unchecked residents in South Australian state capital Adelaide could soon be drinking water with salt levels above World Heath Organization recommendations.

The process started 150 years ago, when settlers first began clearing trees to set up farms along the Murray-Darling river system in southern Australia.

As trees are cleared along rivers, water tables rise, bringing salt naturally present in the ground up to the surface. The salt contaminates agricultural land and is washed into rivers by rainfall.

The Murray-Darling Basin Commission audit found salinity increases in the next 20 to 50 years would cause problems for irrigators, the environment and regional infrastructure.