Measuring Water Leakage from an Artificial Wetland Impacted by Earthquake Fissures

Rice farmers of the Missouri Bootheel are well aware that their flooded fields may leak excessively without explanation. Federal and state agencies are faced with this same perplexity in their attempts to develop artificial wetlands, as multi-million dollar impoundments about the Missouri Bootheel have inexplicably failed to hold water. A design blunder has been determined to be the cause, in that during the design phase only geotechnical soil cores were evaluated, all of which implied a contiguous gleyed horizon that was highly capable of perching water. This project employed ground-penetrating radar (GPR) to locate the cause of the excessive leakage in an abandoned waterfowl impoundment. Our surveys found long and narrow sand-filled fissures caused by liquefaction from the region's reoccurring cataclysmic earthquakes having breached the water-perching horizon. As several million dollars had been expended to construct the impoundment's earthworks and pumping network, site remediation strategies were being sought for reducing the leakage through a fissure. A 0.4-ha test pool and an internet-accessible instrumentation system were implemented within a small section of a failed impoundment, the objective of which was to measure the water loss that was attributable to a fissure. Repeatedly flooded and allowed to drain, the test pool's infiltration rate steadily increased from 4.1 to 6.6 cm d -1 . The field saturated hydraulic conductivity (K(fs)) of the surface horizon was measured to be 22 cm d -1 . Water perched on an underlying gleyed horizon. The K(fs) of a fissure that pierced the perching gleyed horizon was measured to be 400 cm d -1 . This project serves to highlight the inadequacy of solely employing soil cores for determining the suitability of a water perching horizon across vast water impoundments that possess vertical drainage features, and demonstrates the application of continuous geophysical profiling technologies for subsurface profiling of landforms possessing seismic fissures.