Data part, groundwater properties

groundflow_density 1.0
groundflow_phreatic_level 0.0 2.5 15.0 2.5

The groundwater density is $1.0 \frac{1000 kg}{m^3}$. The level of groundwater is constant between ($x=0.0 m$ , $y=2.5 m$) and ($x=15.0 m$ , $y=2.5 m$).