Welaka Spring is a third-magnitude spring with a pool about 90 feet long from east to west and 60 feet wide from north to south. The spring vent is about 20 feet in diameter in the clayey-sand bottom of the central part of the pool, with a prominent boil over the vent. The water from the spring is clear, but the spring water mixes with dark water from the St. Johns River a short distance downstream. The spring pool opens on its southwest side to a run about 200 feet wide that curves to the southwest, then to the northwest for about 1,200 feet to the St. Johns River. Backwater from the St. Johns River, at least in part associated with tidal effects, frequently makes it impracticable to measure the spring discharge.