The capital buffers that banks carry at present might - or might not - prove sufficient to adapt to the demands of Basel 3, the capital and the liquidity wave rolling from the North Atlantic to the supposedly pacific shores of Australian banking.Basel 3, the code-word for a wave of reforms, dictates a new leverage ratio, stringent liquidity rules, an increased core capital ratio, and a series of buffers for systemically critical banks - which includes Australia's big four.The issues are receiving increasingly critical attention, including from sell-side analysts.In the era of the first Basel accord, banks' tier one capital ratios in Australia fell to seven per cent, in 2001, and stabilised around 7.5 per cent during the boom.In the era of the Basel 2 rules, only three years old, banks' tier one capital ratios have climbed to the present average of 9.4 per cent.Of the big four, ANZ has the highest ratio, of 10.1 per cent, and NAB the lowest, at 8.9 per cent.On the other hand, banks like to point to an alternative calculation of their core capital ratios, the method used in Britain. On this measure only three banks exceed the European tier one capital average of 11.4 per cent.NAB is the odd bank out with a tier one capital ratio measured the British way of 11.3 per cent.ANZ, CBA and Westpac have, under British rules, ratios in the 12 per cent to 13 per cent range.NAB's capital levels look on the low side, relative to its peers, on yet another measure.The bank told investors last week that on one definition of the coming capital reforms NAB's present core ratio, of less than seven per cent, was a little below the required levels. One banking analyst sees issues emerging at ANZ and Commonwealth banks as well.Macquarie analyst Craig Turton said the ratio at Commonwealth Bank is likely to be the lowest of the big four banks, and in a "worst-case scenario" could fall to 5.42 per cent.On ANZ, he said the bank's possible acquisition of 57 per cent of Korea Exchange Bank adds a capital-raising risk to mounting evidence of weaker credit growth and margin pressures. The Australian reported on Turton's research yesterday."In the event ANZ were to acquire 57 per cent of KEB, as well as get to a respectable post-Basel 3 core tier one ratio, the bank would need to raise somewhere between $1.4 billion to $5.3 billion," Turton said.Macquarie Group is the fifth bank where the profit season disclosed vulnerability on the capital front.The group mentioned the likelihood of operating with a lower level of surplus capital than has been the case as one way of lightening the overall capital burden.How much lower might this be?It's tough to speculate when Macquarie cannot tell its depositors or shareholders what the capital target actually is.