Water, water everywhere!!!

Intro to groundwater vocab. Before throwing a bunch of unfamiliar vocabulary words at you, let’s get a quick over- view of what we’re even talking about…groundwater. Your textbook states that there’s 30 times more water in the ground, under the surface, than in all the lakes and rivers of the world. So, there’s a good chance that the water you shower in, wash your clothes in, spray on the lawn, and drink may come from an underground source. Let’s see how. I LOVE water! Where’s the pool???

A closer look. Joe and Rex are having fun outside. Now, let’s take a much closer look.

A much closer look. No, we need to look closer.

REAL close Ok, that’s pretty good. What you can see here is how “dirt” and “soil” is often found in layers. There’s really rich soil near the top where there’s a lot of nutritious decaying animal/plant matter. Beneath that might be a more clay-like layer or small pebbles. Beneath that might be layers that are more rocky or even solid rock. The soil and rocks here have pores – empty spaces and cracks. It’s not all crammed together.

And this is important, why???

Groundwater Here’s an easy one to start. Groundwater is water contained in the pores (open spaces) in soil and rocks. THAT’s easy to remember. Imagine it raining on this type of soil right here. If the brown squares are the individual soil particles, what will happen? Yeah, the water will just fill the pores between the soil particles. Easy.

Porosity What’s the difference in the pores in these two pictures? The one on the left has fewer pores and they’re not very big. The soil on the right has more pores and they’re also larger. The soil on the right can hold much more water than the soil on the left. The difference is in the soils’ porosity – the amount of empty space in soil or rock (high = lots of empty space).

Vocab. Words #3 & #4 Now compare these two soils. If it rained on them, in which one would the water slide through to whatever is beneath them the easiest? The one on the left…its pores are far better connected than the one on the right, which looks like it might trap water and not let very much slide through to beneath it. This is a measure of the soil’s permeability, its ability to transmit water through it. A permeable soil has well-connected pores that let water flow through easily. The opposite would be impermeable soil. It would have few pores or pores that aren’t well-connected.

Aquifer So…imagine we stacked a permeable layer of soil/rock on top of an impermeable layer. This is frequently the way things are found in the ground beneath us. What will happen? The water will soak through the top, permeable layer. But when it hits the impermeable layer below, it won’t let it soak any further. The water will sit in the permeable layer like a sponge. This is how an aquifer works. An aquifer is a layer of permeable rock that contains stored groundwater.

Water Table Let’s look more closely at a side view of an aquifer. Permeable layer. Impermeable layer. There. Now we’ve got an aquifer. See that red line? It shows the level of the water soaked in the permeable rock. If it rains some more, it will likely rise up…in a long drought, it will likely lower greatly. This red line represents the water table – the top surface of water soaked into a permeable layer.

Making use of groundwater If you drill a well, you should be fine as long as your well reaches into which layer? Getting the water up is a simple process of using mechanical/electrical devices like:

Artesian Well Sometimes, if you’re observant, you can get water from a well just by…digging the well. No pumping or buckets on a rope. Gravity can be a real driving force, and in sloped terrain like this, it helps to create a pressure (think: force) that can drive water up a well onto the surface. Look, Pa! Water! An artesian well is a well that releases water using pressure (usually because of sloped terrain).

Watershed Study this map: what does it show you? If you guessed aquifers in Texas, that’s a good guess. But that’s not what this is. This is a watershed map. It shows how the major rivers of Texas and all of the smaller creeks and streams that join with those rivers “drain” a portion of Texas. Watershed – the area of land drained by a river and its tributaries.