# Solution Exercise 5

It can be seen that the density does not vary between the screens, so this means the point water hydraulic heads can be used directly in the calculation of *q*_{z }with Darcy’s law. Given the negative numbers, the smallest absolute value is the highest hydraulic head so the hydraulic head increases with depth, thus flow is upward from screen 3 to screen 2. The factor of 1000 in the equation converts meters to millimeters.

While from screen 2 to 1 it is

For the more general case where the density varies, one would first convert the hydraulic heads to freshwater heads using , which yields (three decimals are provided to prevent large rounding errors in the calculation of *q*_{z}):

Screen |
h_{f} |

1 | −2.815 |

2 | −2.679 |

3 | −2.542 |

Using one finds for the flow between piezometer 3 and 2:

And for the flow between piezometer 2 and 1

Which is the same answer as before (note that the unrounded result has a 0.43 percent error because *K*_{f} was equated to the hydraulic conductivity).