This is a spring that falls dry several times or most of the year. In general seasonal spring means it is dry every year during a certain season, normally summer and autumn, sometime dry season. Actually this depends much on the climate and the amount of rain. A subtype are ephemeral springs, which fall dry only for a short time.
In most cases these springs are situated above, but near to the groundwater table. As the groundwater table moves inside the rock over the year, it sometimes reaches the spring and the water starts to flow. When the water table falls during dry seasons, drained by other springs nearby, those with the highest level fall dry.
As very wet years often result in crop failure, the production of some wells were counted as a bad omen. The Hungerbrunnen (famine well) in Germany is a typical example. However, modern research could not find a significant correlation between the flow of the spring and the yield.