Final answer:
Increasing the amount of precipitation leads to an increase in runoff, as more water is available to flow over the land surface.
Step-by-step explanation:
If you increase the amount of precipitation, the runoff increases. This is because as more precipitation falls, more water is available to flow across the surface of the ground. Precipitation that does not evaporate, transpire, or infiltrate into the ground becomes surface runoff. The volume of runoff will increase with the amount of precipitation, assuming other conditions such as soil saturation and land cover remain constant.