Consider the borehole record below (in particular the *Water Depth* column).

There is a black inverted triangle at a depth of 2.50 m. What is the meaning of this symbol?

There is a white inverted triangle at a depth of 3.20 m. What is the meaning of this symbol?

Why has a range been given to the depth of the water table?

[![borehole record][1]][1]


  [1]: https://i.sstatic.net/69cLL.png