Well, well, well…

Rainwater, stream water… what about groundwater? This was one of the pieces of my project that. although being central to my research question, came into play fairly late in the game. I want to prove that not only 22Na provides an accurate age for water, but that it can provide accurate ages at a greater resolution, along a single groundwater flowpath. The diagram below illustrates one single flowpath. Water enters at a point on a slope, and as it travels through the ground, is youngest at point A, getting older and older until it eventually enters the stream. If I were to sample water from points A, B, and C, would aging the samples with 22Na provide successively older ages? This is the question I am still trying to answer.


fig (2)

To explore this, I installed a series of wells within the Pagonia watershed. The well I initially installed at the top of the ridge (my “point A” well) did not hit the water table, and I had to move further down the slope to be successful. I also installed a well at the bottom of the valley, upstream from my stream sampling site, as well as sampling from a well previously installed right next to the stream. I took many samples from these wells over the course of the summer, and am slowly forming a hypothesis about how groundwater moves in this watershed. I will soon drill a well right at the ridge of the watershed, in pursuit of sampling the very youngest groundwater in the watershed. This will be done with a drill rig attached to the back of a truck, rather than having to drill the wells with an auger by hand! I’m looking forward to moving forward in sampling groundwater in the Pagonia watershed, and testing the reliability of 22Na-given ages in the area.


  1. This might have been answered in an earlier blog, but what is the importance of testing the age of groundwater? Is it to determine the path it takes while traveling through the watershed, or does it have to do with the chemical content of the water?