The storage height of a small homogeneous earth dam is 16m, and the flow network is shown in Figure 1-5. The interval of the water head gradient equipotential lines in the flow network is evenly divided into m=22 (the number of equipotential lines calculated from downstream is shown in the figure). The G point in the earth dam is located on the 20th equipotential line, 11.5m above the ground level. May I ask which of the following options is the closest to the pore water pressure at point G? ()<image 1>
['30kPa', '45kPa', '115kPa', '145kPa']