With substantial rain falling in the Cowra district over the weekend the question is often posed how high is the Lachlan and how much water is actually passing by the town.

Now the answers can be found in a new online information hub on WaterNSW's website in an Australian first.

The hub uses the latest technology to enhance the transparency of the state's river operations and water management across the Murray Darling Basin that not only supports agribusiness and protects environment water, but satisfies key reforms recommended by recent government reviews.

The river systems are broken down to each valley with real-time information on allocations, storage, environmental flows targets, interstate shares with some data dating back 30 years for comparison.

Along the Lachlan, users can find out what access is available as well as how much water there is up stream in storages.

For example after last weekend's rain the portal showed the river level height at Cowra on Wednesday as 3.1 metres.

The portal also showed that the flow rate at Cowra was 5,220 megalitres a day.

Further down the Lachlan, on Wednesday, the Lachlan at Forbes was 3.2 metres.

In other rivers, users can find out how much water remains in the accounts and what access arrangements there are.

It has taken the government two years to put the online hub together with more information being added from user feedback about what they want to know.

At this stage the hub mostly focuses on regulated rivers with plans to include more information about unregulated rivers and floodplain harvesting.

Water Minister Melinda Pavey said the new portal provided a bird's-eye view of river systems along with all priority information at a glance, including river flows, dam storages, water availability and weather outlook.

"This is a critical step in enhancing transparency in the water sector, it is a historic step forward in transforming the water sector for all users," Mrs Pavey said.

"With this new technology people can now see exactly what is happening in any major river valley, as well as having at their fingertips all the relevant information as to how that river is being managed."

Mrs Pavey said the website brought together information across the entire water sector and coupled it with a realistic view of the river itself so users could see where and when water was flowing.

"This is not only a major asset for farmers seeking certainty around when they can and can't access water, it is an invaluable tool for anyone seeking a comprehensive insight into the management of our river network," Mrs Pavey said.

"In unregulated river systems, where water availability is governed by river volume, licence holders now have a clear picture of the prevailing water situation, especially in the case of a significant rain event which may generate flows."