Artesian Wells come from a confined aquifer. This is an aquifer that has layers of impermeable material both above and below it and is under pressure so that when the aquifer is penetrated by a well, the water will rise above the top of the aquifer. A pump is not needed to draw the water up. Runoff is the water from rain and snow that does not sink into the earth. Instead it moves across the land surface to its watershed.
Erosion is the movement of soil by water.