Not long ago, water ministers talked about delivering the Murray-Darling Basin Plan "on time and in full". You don't hear that language so much anymore.

Now the ministers will discuss a "plan for the plan". It's because the states have fallen so far behind. Under the watch of the previous Coalition government, work to revive our rivers simply languished.

The Murray-Darling Basin Plan was implemented almost 10 years ago. But the fact is, today it is hobbling towards the finish line. It's been a slowdown since 2014.

With only 20 months to go, Victoria and NSW have signalled that they won't reach their water targets by June 2024 - which require them to set aside 3200 billion litres of water for the environment and make sure it can flow into dry wetlands and billabongs.

In order to fully understand why the plan is failing, we need to look at why it was implemented in the first place. Rivers of the Murray-Darling Basin are dying. Climate change is making things worse, but this is a disaster that has been unfolding for years.

The easiest way to think about it is to look at the changing rhythm of the river. Historically, rivers relied on regular floods. The river would swell from snowmelt and rainfall, spilling overbank into wetlands and billabongs.

But this rhythm has disappeared. Now the river acts more like a channel, carrying water from upstream dams at a fast and consistent level to corporate irrigators.

Part of this is because large dams and weirs captured those seasonal inflows. Another part is excessive irrigation and climate change. Many rivers struggle to reach their end with half of their water left, some with any water at all. This becomes catastrophic in a hotter, drier climate. Runoff into rivers has halved in recent years.

The basin plan was an effort to restore this cycle of smaller floods that fish, birds and River Red Gums depend on. To make sure wetlands, at least some of the time, are wet.

But the work hasn't happened. There's not enough water set aside to get into wetlands that need it. Victoria and NSW haven't done much-needed work to let the water flow into them. It's been stuck in the channel.

The sad result is that all that water, held for the common interest, can only reach about 2 per cent of the floodplain.

This week's water ministers meeting will focus on this work that hasn't been done. States haven't brought water use down to sustainable levels and they haven't let that water flow over the banks, across the floodplain.

But there's more. Victoria and NSW have unfinished projects that were cooked up to delay and avoid giving rivers water altogether.

They're arguing to push back deadlines for their convoluted offset program. It's based on the idea that they can save wetlands with less water. But they'll need a few years more to re-engineer the landscapes of national parks, forests and reserves along the river for greater "water efficiency". It's a massive experiment with weak science behind it.

Victoria and NSW know these dodgy offset projects won't be done in time. They were proposed because both states never intended to set aside enough water for the basin's survival in the first place.

Now Ms Plibersek has a chance to do what her Coalition predecessors were too sheepish to do - bring the states in line, cutting the delay tactics.

The wetland engineering offset projects are failing. The existing deadline should be a hard test to knock them off and get back to work. Buckling now only locks the Murray-Darling into more years without the water it needs. Just three years without water in wetlands is enough for some fish to become locally extinct.

There's a clear path forward. First, standing by the deadlines in the plan. Second, returning water quickly and responsibly. This means buying it from the many irrigators ready to sell part of their share. Third, working out a genuine plan to let the water flow.

Right now, Victoria and NSW will only commit to something if it means less water for the river. But that approach simply won't cut it.

If legal deadlines and the basin's survival aren't enough of an incentive, then Ms Plibersek needs to reach for other tools.