Exercise 3: GMS modelling

Consider the groundwater reservoir outlined in fig. 1. Groundwater is flowing from well no. 1 to well no. 2. It is assumed that the flow is 1-dimentional and steady state. In the region between well no.1 and well no.2 four different soil types are present – each with different hydraulic conductivity, K_a, K_b, K_c, K_d.

K_b

K_d

K_c

K_a

Figure 1: Vertical section of groundwater reservoir.

Please answer the following questions:

Question 1: Describe the flow problem in GMS using the grid approach. Discritize the flow domain into 2 layers of each 5 m thickness. Use a cell size of 5 m in the x direction and 1 m in the y direction (perpendicular to the paper).

The hydraulic conductivity for each of the four different soil types are determined to

K_a= 0.01 m/s

K_b= 0.005 m/s

K_c= 0.1 m/s

K_d= 0.002 m/s

.

Question 2: Compare the computed head with the results from exercise 1 and 2

Question 3: Reduce the cell size to 2.5 m in x and z direction, recalculate and compare the results.