DPVE removes contaminants from above and below the water table. Avoiding sites with a high water table is crucial. It is also water that is flowing within aquifers below the water table. "Dredging" is a method for mining below the water table. Pulaka is grown in large pits of composted soil below the water table. Air sparging involves the injection of air under pressure below the water table. Matrix potential only occurs in unsaturated soil above the water table. Excavation was difficult due to saturated clay and high water table. The depth to the water table is generally about . Both mechanisms reduce the amount of recharge water that reaches the water table. For example, mining affects groundwater and water table levels and acidity. The lower town is subject to a rising water table. Common approaches for providing oxygen above the water table include landfarming, composting and bioventing. Hence, hydrostatic water pressures are negative above the water table. In certain areas it has resulted in a significant lowering of the water table.