The importance of clean groundwater is pretty universal, about half of the world's population uses it for drinking water. However, ensuring that groundwater is clean and salt-free usually requires installation of a permanent monitoring well, a costly and often impractical process. Installing a well requires drilling equiptment, the wells aren't cheap, and they often get destroyed.
Conversely, measuring the salt content of a soil sample is a fairly simple process. It's temporary, doesn't require much equiptment, and you dont have to worry about landowners or animals destroying your handiwork. A while ago I published a paper on how to estimate the salt content in groundwater from soil samples. I've been learning JavaScript lately, so I made a tool for estimating groundwater quality from soil samples based on my findings. If you work in the environmental industry, hopefully you find it useful.