Mr Howard called the summit -- to be held in Canberra tomorrow -- with invitations to the premiers of the Murray River states, NSW, Victoria and South Australia, all of whom promptly signalled acceptance.
The Prime Minister said Queensland Premier Peter Beattie is also most welcome to attend after complaining he was not invited.
Mr Beattie also urged Mr Howard to hold a special Council of Australian Governments (COAG) meeting to discuss climate change and the impact of the worst drought on record.
Murray-Darling crisis
Mr Howard called the summit after new data showed flows into the Murray-Darling Basin this year had also been the worst on record, leading to warnings the three dams underpinning the basin's southern irrigated farmlands would run dry within six months.
Snowy Hydro has also warned it will not be able to meet its minimum flow down the Murray and Murrumbidgee rivers.
The renewable-electricity provider has informed the NSW Irrigators Council that flows into the system last month were half the level of the previous record low, The Australian reports.
"The serious water situation in the Murray-Darling Basin requires a collaborative response from both federal and state governments," Mr Howard said in a weekly radio address.
"This prolonged drought is having a terrible impact on farming communities across Australia especially in the Murray-Darling Basin, and has inevitable consequences for city dwellers.
Mr Howard's Parliamentary Secretary for Water Malcolm Turnbull, who is expected to play a key role in the summit, said it would focus on ensuring irrigated farmlands and towns did not run out of water.
"By the end of the irrigation season in April or May, the big dams on the river ... will be just about empty," Mr Turnbull told the Nine Network.
Mr Turnbull said he was not interested in blaming irrigators for the Murray's woes and was sceptical about governments being able to decide what crops farmers should plant.
"I don't think an Australian government crop selection committee would make the right decisions," he said.
But Mr Turnbull agreed this drought, which has lasted for six years in some regions, had been worsened by the demands of irrigators.
NSW Premier Morris Iemma said it was right for drought to be considered a national problem while South Australian Premier Mike Rann said he would use the summit to ensure water reached the bottom of the Murray-Darling basin.
Victoria's caretaker premier Steve Bracks, who will fight a state election on November 25, said he would attend the summit "in caretaker mode".
"Water is such a big issue and of course we will play our part in assisting our interstate colleagues and also the Commonwealth," Mr Bracks said.
Federal Labor leader Kim Beazley said only the Commonwealth had the resources to address the looming crisis.
"Water must be dealt with on the basis of Commonwealth leadership," Mr Beazley told reporters in Perth.
However, Labor's environment spokesman Anthony Albanese declared the summit to be little more than diversionary since it coincided with the Melbourne Cup and the central bank's meeting to decide interest rates.