Problem 7 Solution
Questions:
a) A piezometer is inserted into an aquifer beneath sediment (low K) of a lake, and water rises to a stable level as shown below. A water table is present but not shown. Is water flowing upward or downward through the sediment? Explain.
b) Draw a schematic representation of the vertical head profile, extending from the water level of the lake to the well screen.
Solution a) The hydraulic head at the point of measurement (the screen interval) in the piezometer is equal to the elevation of the water level in the piezometer. The hydraulic head at all depths in the lake water is equal to the elevation of the lake surface. Therefore, the head below the sediment is higher than above the sediment, so flow moves upward through the sediment, because water moves from higher head to lower head.
Solution b) The vertical head profile shows the constant head in the lake and the upward gradient in the sediment. The head gradient also has an upward component in the aquifer, but the hydraulic conductivity is higher, so the gradient is not as large (it is less steep).
