Local recharge through sinkholes and drainage wells moves underground

With the artesian level as much as 100 feet above sea level and the land surface is seldom more than 200 feet, a Sabal Trail pipeline drilling frac-out wouldn’t have to go far to get into the Floridan Aquifer groundwater used by wells around here. We already saw such water contamination would go underground is hard to predict. This is not news: here’s a paper from 1966 with the main points.

Artesian Water in Tertiary Limestone in the Southeastern States, By V. T. Stringfield, GEOLOGICAL SURVEY PROFESSIONAL PAPER 517, 1966.

The piezometric surface, or the height (with reference to sea level) to which water in an artesian aquifer would rise in wells, shows the chief areas of recharge and discharge and direction of lateral movement of the artesian water. In general, the high areas of the piezometric surface indicate recharge, and the low areas indicate discharge. Recharge may, however, occur in some of the areas of relatively low pressure. The piezometric surface ranges from sea level near some coastal areas to more than 120 feet above sea level in the lake region of central Florida and in the Jackson County area in western Florida. The piezometric surface is as much as 250 feet above sea level in an outcrop area of the aquifer, extending from southeastern Alabama northeastward across Georgia to South Carolina.

The aquifer is recharged, not only in areas where it is at or near the land surface, but also where the overlying beds have been penetrated by sinkholes. In general the piezometric surface slopes to the east, southeast, and south from the high area in Georgia. In the Valdosta area in Lowndes and Brooks Counties, where there is local recharge through sinkholes and drainage wells, the piezometric surface is as much as 100 feet above sea level.

The lateral movement of water is generally from the recharge areas. Although the lateral movement may be controlled over considerable distances by geologic structure and the movement may be parallel to the dip of the formations, the relative positions of the recharge and discharge areas are more important than the geologic structure in controlling the direction of the movement of the water in the area of this report. …

Joints or fractures and bedding planes may have a pronounced effect on the patterns and movement of water in limestone and associated rocks. Solution features, such as vertical pipes or natural wells, in the limestone appear to have formed in the zone of aeration at the intersection of two sets of joints. Long shallow vertical openings were formed along some joint planes. Lateral movement may be locally along bedding planes, but the movement generally does not appear to be affected by regional structures. The cavities and horizontal solution channels were formed chiefly in the upper part of the zone of saturation, nearly parallel to the hydraulic gradient.

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