Over the past decade the microbial quality of many local rivers used for irrigation of fresh produce has decreased. Picture: Karen Sandison

Johannesburg - The Vaal River system is at “significant risk” due to unlawful water use, acid mine drainage and municipal water losses, Business Day newspaper reported on Friday.

The river supplies water to 60 percent of the country's economy and 45 percent of the population.

Water Affairs spokeswoman Linda Page said unlawful water use last year was estimated at 244 million cubic metres.

“We know that the biggest culprits are farmers in this area,” Page told the daily.

Non-revenue water (water not billed for by municipalities through loss and errors) comprised about 36 percent of total water use.

To sustain water, South Africa needed to eradicate unlawful irrigation by next year and implement the second phase of the Lesotho Highlands Water project, the newspaper reported. - Sapa