The supervising scientist for the region covering the Ranger uranium mine says higher-than-usual salt levels in a creek downstream of the mine do not pose a health risk and were not hidden from traditional owners of Kakadu National Park.

Alan Hughes was questioned about the salinity spike at senate estimates in Canberra yesterday.

He said there was a spike in salinity levels because run-off water from a retention pond had spilled into a billabong connected to the creek, but no significant uranium was detected in the water.

"The uranium content of that retention pond is quite low. It's of the order of five micrograms per litre," he said.

"Drinking water standard is 20 micrograms per litre, so it's better than drinking water standards when it comes to uranium content."

Traditional land owners say they are against the proposed expansion of the uranium mine until environmental monitoring is stepped up.

Mr Hughes says the creek is continuously monitored, but only weekly data is available on the website at this point.

"Because we're still ironing out some of the bugs in the system - it's hardware issues, software issues, IT issues, things like that - we're still not ready to do that just yet but the information is there and it's extremely useful," he said.

But Greens Senator Scott Ludlam says there have been 150 reported leaks from the mine since it opened and it is proof mining company ERA should be forced to conduct continuous monitoring.

"You have contamination spikes and the kind of scares that were reported in the press over the weekend that completely go under the radar if you're only looking at a weekly average or a monthly average," Senator Ludlam said.

"The importance of the real-time monitoring is that you can see when these events happen, you can pick them up when they are occurring."

The data from continuous environmental monitoring is expected to be put on the website from next year.