Humans impact the water cycle by polluting the water in rivers, streams, reservoirs etc.
We are polluting it with harmful chemicals and disgusting substances. Technically we as humans cannot alter the water cycle, however, we can mess it up by dumping waste into the ocean.
When we talk about the water cycle moving water vapor in and out of the atmosphere, there are no human activities that can affect that. Water vapor will still evaporate into the atmosphere whether the ground water is dirty or clean.