There isn't one for the word supply, as used in your sentence/ situation, you just need an adjective before supply. to stress that there is insufficient supply. 'water pressure' could be what you are looking for. I would like to draw your attention to the lack of water pressure. Resulting in the water supply being irregular. Resulting in the water supply being irregular. Resulting in the irregular supply of water, caused by the lack of water pressure. however, the problem may not be water pressure it may be a blockage​ or many other things.

If "supply" is a verb (ex. "to supply goods"), then a possible antonym would be "to withhold". However, in the sentence you provide, "supply" functions as a noun ("the water supply"). "Supply" as a noun doesn't really have an antonym. It is similar to words like "amount," "weight," and "size." I don't know exactly how to explain this, but notice that all these words describe a general notion of measurement, and can be described by antonymous adjetives: Heavy weight / light weight a large size / a small size a large amount / a small amount an abundant supply/ an insufficient supply If you want to negate a phrase like "regular supply" you would negate "regular" (i.e. use "irregular") rather than change "supply." I hope this helps.

Hey I think you are referring to shortage of water supply. SUPPLY is being used as a verb so you can add an adverb to describe your situation or is it the direct antonym you are looking for? It might be DEMAND, the demand of water is not met. or the word DEPLETED can be used in the context as well as the word SEIZED. Do tell if you have found the word. Cheers