The Groundwater Foundation has many useful tools to help show how everything we do affects groundwater and how groundwater affects everything we do. One of Frannie’s favorite tools is the Awesome Aquifer Kit, which lets her get a closer look at what happens to water when it’s deep in the ground. In this series, Frannie will show us how to use the Awesome Aquifer Kit and what it means in our lives.
This week in Frannie’s exploration of the Awesome Aquifer Kit is all about groundwater and surface water interactions.
First, we have to set up our aquifer by pouring gravel into a clear container and spreading it out evenly. The gravel represents the land and an unconfined aquifer. An unconfined aquifer is groundwater that is below porous material like soil, sand, and gravel.
|The gravel is flat and we have already added some water to our container.|
We'll be using the syringe next time!
Let’s start by slowly pouring water near a wall of the container. Watch as it infiltrates, or flows from the surface into the ground, and fills th
e spaces between the rocks of the whole container. Stop pouring when about half of the gravel is saturated. We can imagine that the pouring water is rain and we are recharging, or refilling, our aquifer.
Do you see that line in the gravel where the water stops? That’s the water table. The water table is the top of the groundwater and it separates the saturated zone, which is completely full of water, from the unsaturated zone, which as little or no water.
Next, let’s scoop some of the gravel to the side of the container to create a lake. Surface water is the water that’s above the surface of the land, including lakes, ponds, rivers, streams, and runoff.
|The top of the blue line is out water table.|
When we add water to the top of our hill, the
water table goes up and fills our lake even more.
We can slowly add some more water, first at the wall close to our hill and second at the wall close to the lake. Watch the water percolate through the gravel and become groundwater. The level of the water in the ground rises, but so does the level of water in the lake. That’s because the groundwater discharges, or flows out, into the lake.
When we add water to the lake, the water table also rises. When groundwater is located close enough to surface water to be recharged by it, then we can say that the groundwater is under the direct influence of surface water.