Sainte-Colombe-sur-Loing

This picture is the source of the River Loing. The river meanders from the village in Burgandy through the department of Seine et Marne and lovers of painting may have heard of Moret sur Loing where a number of Impressionists, notably Alfred Sisley, used to paint by the side of the river.

When I saw this improbable 'spring' I wondererd where the water actually sprung from as there are no mountains nearby. Would it be an underground aquifer? I thought water didn't flow upwards.