"Hotter drier summers and less predictable rainfall – two effects of a changing climate – plus over-abstraction of water for industry, agriculture and the public water supply as the population grows, is a toxic combination", Bevan said in a keynote speech at the Royal Society.
The Environment Agency estimated that summer rainfall will decrease by approximately 15% by the 2050s in England, and up to 22% by the 2080s.
The agency also suggested that summer temperatures in the south of England could regularly surpass 35 degrees Celcius (95 Fahrenheit) and start to hit 40 degrees.
"Nature is interconnected. As climate change is causing more extremes in one part of our environment, these are colliding with other effects. So drought risk brings other risks as this domino effect plays out", Bevan said, as he called for an increased focus on water quantity, rather than just water quality.
His warning came ahead of the UN Conference on Climate Change (COP26), to be held in less than two weeks in the Scottish city of Glasgow, where world leaders are expected to agree on measures necessary to limit global warming to 1.5 degrees above pre-industrial levels.
The UK environmental agency boss said, however, that regardless of the outcome of the COP26 and "even if the world stopped all carbon emissions tonight," the UK needs to be resilient against future hazards and potential shocks, because some "irrevocable" climate change has already happened and will continue to happen.