The variable elevation of the groundwater table in the St. Louis area was estimated using multiple linear regression (MLR), ordinary kriging, and cokriging as part of a regional program seeking to assess liquefaction potential. Surface water features were used to determine the minimum water table for MLR and supplement the principal variables for ordinary kriging and cokriging. By evaluating the known depth to the water and the minimum water table elevation, the MLR analysis approximates the groundwater elevation for a contiguous hydrologic system. Ordinary kriging and cokriging estimate values in unsampled areas by calculating the spatial relationships between the unsampled and sampled locations. In this study, ordinary kriging did not incorporate topographic variations as an independent variable, while cokriging included topography as a supporting covariable. Cross validation suggests that cokriging provides a more reliable estimate at known data points with less uncertainty than the other methods. Profiles extending through the dissected uplands terrain suggest that: (1) the groundwater table generated by MLR mimics the ground surface and elicits a exaggerated interpolation of groundwater elevation; (2) the groundwater table estimated by ordinary kriging tends to ignore local topography and exhibits oversmoothing of the actual undulations in the water table; and (3) cokriging appears to give the realistic water surface, which rises and falls in proportion to the overlying topography. The authors concluded that cokriging provided the most realistic estimate of the groundwater surface, which is the key variable in assessing soil liquefaction potential in unconsolidated sediments.

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The Taum Sauk Pumped Storage Powerplant in Reynold County, Missouri (USA) was constructed between 1960 and 1963 to store water for generation during peak daytime power demands. The plant consists of a lower reservoir, which is sited along the East Fork of the Black River, and an upper reservoir, which is formed by a kidney-shaped rock-fill dike approximately 50 to 87 ft (15.2 to 26.5 m) high, capped by a 10-ft (3.05 m) concrete parapet wall set on crest that is 12 ft (3.66 m) wide. The Upper Reservoir held 4,600 acre-ft (5.67 billion liters) when filled. A variety of design/construction flaws, an instrumentation programming error, and human errors contributed to a catastrophic failure of the Upper Reservoir on December 14, 2005. Malfunctioning and improperly programmed and/or placed sensors failed to indicate that the reservoir was full and did not shut down the facility's remaining pump unit until water had been overflowing for 6 to 7 minutes. This overflow undermined the parapet wall and scoured the underlying embankment, leading to a complete failure within that time frame. The peak discharge from this outbreak flood was estimated to be 289,000 cfs (8,184 m 3 /s), obliterating most of Johnson Shut-ins State Park, where, miraculously, only five people were injured. The flood pulse was significantly mollified by capture within Lower Taum Sauk Reservoir, and the maximum discharge over the Lower Taum Sauk Dam was limited to just 1,600 cfs (45.3 m 3 /s), precluding any significant downstream damage.