The phrase "an overwhelming source" is correct and usable in written English.
It can be used to describe a source that provides an excessive amount of information, influence, or power in a particular context.
Example: "The internet has become an overwhelming source of information, making it difficult to discern what is accurate."
Alternatives: "a vast source" or "a significant source".
"My supervisor, much to my surprise, was an overwhelming source of support," she wrote.
However, in spite of this support, many students in introductory computer science courses still find programming to be an overwhelming source of frustration.
The most significant contributors to cancer risk were mobile sources such as on-road vehicles, airplanes, and trains, with diesel emissions an overwhelming source of pollution.
The latter derivative-fit approach is able to remove crustal contamination which is the overwhelming source of error in determining a main field model (Cain et al. 1965; Dawson and Newitt 1978).
Any substantial change in the concentration of oxygen is going to be intimately linked to an equally significant change in Earth's biota since the overwhelming source of O2 comes from the photobiological oxidation of water.
The overwhelming source of carbon dioxide is the burning of oil, coal and other fossil fuels.
We all know that the economic crisis is the overwhelming source of today's budget deficit (except for those who have a political incentive to believe otherwise).
The overwhelming source of that growth was the housing boom — which had nothing to do with either the 2001 tax cut or the 2003 tax cut.
This effect has been the overwhelming source of the increase in polarization since the 1970s, Gerrymandering cannot account for this form of polarization.
But the survey, put out by the Online Publishers Association, an industry trade group, also shows that a relative handful of businesses benefit from these purchases and that advertising remains the overwhelming source of income for supporting digital content.
