About WET | Program Planning | Events | Outcome and Evaluations
A total of about 30 six-grade students from D.C. Wolfe Elementary participated in the Fall 2007 WET event. They were divided into three groups and rotated through three modules ( groundwater/geology, rock art and descriptive writing, and soil studies) during the field day. The WET groundwater/geology module includes four activities: aquifer in a tank demonstration, porosity and permeability testing, permeameter experiment, and DO measurements. Below is a list of WET activities. Click on each one of them for a breif description of the activity.
The WET team builds a physical aquifer tank model (Figure 1) to demonstrate the following hydrology concepts:
Figure 1. An aquifer tank model built to demonstrate groundwater and surface water interaction and groundwater contamination. Students can see and mark saturated zone, water table, unsaturated zone, and surface water body in the model. They also examine the well screen, recharge the aquifer, and pump water from well.
Students were asked to compare differences in porosity and permeability of three common aquifer materials – gravels, sands, and clays. For porosity assessment, they added fixed volumes of water into three beakers which are 60% filled with dry gravels, sands, and clays, respectively. They compared the amounts of water ponding above sediments after water completely percolates downward and fills up open pore spaces between solid sediment grains (Figure 2). They observed that gravel-size sediments have the greatest porosity because they can hold and store more water than sand clay-rich sediments. They also compared how fast water can flow through gravels, sands, and clays. They prepared three “aquifer in a syringe” settings which allow water to flow through gravels, sands, and clays under the same hydraulic gradients when the plugs (filter stops) at the bottom of syringes are removed simultaneously. There is hardly any water flowing through syringe filled with clay. They concluded that gravels are most permeable as water is drained much faster through the syringe.
Figure 2. Students assembled “aquifer in a beaker” and “aquifer in a syringe” models to compare the porosity and permeability of gravel, sand, and clay-rich sediments.
We assemble a constant-head permeameter (Figure 3) to simulate Darcy's experiment, allowing students to visualize flow and contaminant (a juice coloring is used) transport through a sand layer under a given hydraulic gradient. The chamber is one piece acrylic to permit viewing of the aquifer sample. An adjustable constant head reservoir is mounted to the upright scale and its height can be easily adjusted to change hydraulic gradient. The greater the hydraulic gradient, the faster the water moves through the sand chamber.
Figure 3. Darcy's experiment setup for a permeameter. Water level difference in a constant-head funnel and a graduated cylinder pushes continuous water flow through a sediment chamber. Outflow from cylinder is collected to estimate flow rates.
Titration analysis for dissolved oxygen (DO) was conducted on a surface water sample collected from a swamp near the Horticultural unit of the E.V. Smith Center . Various dissolved oxygen reagent powders were added into water bottle. The presence of brownish-orange precipitate and yellow water color indicate oxygen is present. Sodium Thiosulfate solution was then added one drop at a time until the water sample becomes colorless (Figure 4). The total number of drops of titrant was counted as the total dissolved oxygen (in mg/L). Students identified if the presence of low, medium, or high for DO in the water. A clean surface water should contains high DO (>10 mg/L).
|Figure 4. Geology student Kyle Lewis demonstrates the use of HACH testing kit to determine dissolved oxygen content in a swamp water sample collected from the E.V. Smith Center.