During the course of the year we have been loosely focusing our science around the larger topic of water. In social studies, we also began the year investigating physical geography through the use of a terrain model, based on the work of Sam Brian at Bank Street College of Education. In our work with water, we looked at properties of water, the chemical composition of water, and how water moves throughout the land to form various geographical structures such as rivers, inlets, and bays. As part of a larger unit on Lewis and Clark, we looked at the Mississippi and Missouri Rivers and the role they played in the exploration of the West. Then, students chose a world river and each researched and wrote about this body of water. They were asked to discuss the geography, history, flora, fauna, and culture of the people along the river. Students in the class chose a wide variety of world rivers for this research project: the Amazon, the Mississippi, the Colorado, the Nile, the Rhine, the Congo, and the Niagara to name a few.

During the week prior to beginning with the tanks, we conducted an experiment in order to learn more about permeable and impermeable substances. We used pebbles, typical sand, fine grained sand, and clay in four different funnels. The bottoms of each of the funnels were covered with cheesecloth and water was poured through the funnels. Students compared the amount of water that was or was not permitted to pass through the various substances. Students worked on this experiment in small groups at their tables, before returning to the rug for a discussion about our discoveries.

One model was placed on a high stool at the front of the room and the students were congregated on the rug. We reviewed the work done with the funnel experiment during the previous week. Then I asked the students what they thought we were going to do with this model. (Many had asked early the previous week if they were ant farms, noticing the cross section and the sand.) Most students had few predictions, even having the various parts labeled and visible. A few students noticed the word lake so they thought there would be some work with water. When I confirmed that we would be working with water, they then wanted to know how we were going to get water into the lake. Were we going to pour water directly into the lake from the top of the model?

We discussed how this was a cut away cross section of the earth underground and that we would be working with water in the tank and noticing things about how the water moved through the tank. In order to watch the water move, we would be coloring it various colors using food coloring. I demonstrated how a jar could be filled with water and turned upside down to insert into the left side of the tank. The kids were clearly interested in watching the water move down the tube until it was filled and then watching the water level drop again as the water was absorbed into the sand. I posed the following questions to the students:

• What do you think this water in the jar represents in nature?
• Why do you think the water filled the left side bar to the top but then the water level dropped?
• Why didn t the water level continue to drop until the side bar was empty again?

The students commented that the jar represented rain or a hose pouring water onto the ground. I added that it could also be melting snow, so we would call the jar the water source as a general way to include all of those ways that water gets into the ground. We then talked about the water level on the left side dropping because the water was being absorbed into the sand. Many wanted to examine the model up close to see how the water was actually leaving the tube and entering the sand. They were unsure why the water level didn t continue to drop any lower than it did, so we left that as a question to investigate.

I explained the instructions for working at the tables:

1. Fill your jar with water, insert it into the left side bar, and observe the results.
2. Mix three cups of colored water, one with blue food coloring, another with green, and a third with red.
3. Inject two syringes of green water into the black injection well and observe the results.
4. Inject two syringes of blue water into the blue injection well and observe the results.
Inject two syringes of red water into the red injection well and observe the results.

Observations Made by the Students:

• The green dye appeared in the lowest gravel layer.
• The green dye traveled very quickly across to the right.
• The blue dye appeared in the sand.
• The blue dye traveled fairly slowly across to the right.
• The red dye appeared in the coarse wedge gravel.
• The red dye traveled very quickly across to the right.
• In some of the tanks, the left side bar of water filled with green water when green was injected.
• The lake area became green quickly in some of the tanks.
In some tanks the lake water also became red and blue, but this took a bit longer than for the lake to turn green.
• When green water was injected into the black injection well, the A piezometer bubbled up sometimes.
• When blue water was injected into the blue injection well, the B piezometer bubbled up sometimes.
• When red water was injected into the red injection well, the C piezometer bubbled up sometimes.
• The faster water was injected into the injection wells, the more the corresponding piezometer bubbled up.

For the second day of work with the model, we spent the time sketching the tank design. Each student was given a blank piece of typing paper and asked to sketch everything important to the operation of the model. Each was encouraged to label relevant parts and use colors when appropriate to indicate the flow of various dyes. (Each table did reinject the three colors into the injection wells so students could include these observations in their sketches.) The detail with which students approached this activity was quite varied. Some students completed their sketches in twenty minutes or so. Others used an entire forty-five minute period and then did some additional drawing the following morning for roughly thirty minutes.

We began by having a few students share their sketches of the groundwater tanks. I made overhead transparencies of the work and a few volunteers came to the overhead and explained some portions of their sketches. We then hung all of the sketches on a side bulletin board for reference during the remainder of the work on the tanks.

I distributed a three-page chart of questions generated by the students during the previous two sessions of work with the models. It was formatted as a two-column chart similar to the one in the previous days explanation, however, the entire Proposed Answer column was left blank. (Please see attached list of questions.) I explained to the students that they were able to spend the day investigating the questions with the students at their tables. They could inject dye into the model if necessary, pump water out of any of the wells, etc. depending upon what they were investigating. They did not need to answer all of the questions, but rather they were to choose those for which they already felt they had an answer and those that interested they in further testing. The majority of the students attempted the questions in the order they were listed on the paper, even though I encouraged them to read over the entire list and skip around.

Closing

At the end of the day's session, I asked the students to highlight one question each was interested in further investigating. It could be a question from the day s list or another question that developed during the day of investigating. For the following day, we created inquiry groups based on the questions students were interested in pursuing. I grouped the questions by topic. Some kids were very interested in further studying the pumping wells and artesian wells. Others wanted to study the leaky landfill. Some were fascinated by the methods for draining water out of the model. Some wanted to study connections between the various piezometers and the injection wells. Because I wanted to demonstrate a number of things with the leaky landfill, I asked the students interested in that topic to choose another question for investigating.

On the fourth day of work with the model, the students divided into groups based on their topics of interest. I asked each group to formulate a list of three or four related questions that the group was interested in investigating. Then they needed to decide what they were going to do to the model in order to produce some results that would help them answer their questions. Then they performed these experiments and recorded the observations. Finally, the group was asked to make some conclusions based on their inquiries. These conclusions needed to refer back to the group s original three or four questions. The sheet on the following two pages was used as a guide for each group to record this work. Some groups also chose to make sketches of various portions of the model.

Groundwater Tank Inquiry Groups worksheet in Word format
Groundwater Tank Inquiry Groups worksheet in PDF

On the following day, many of the groups wanted to continue working on pieces of their investigations. I told each group that it could continue experimenting for ten or fifteen minutes and then the remainder of the science time would be spent making posters of their discoveries to share with the other groups. The class is very familiar with this format of sharing strategies in math, so it seemed very natural to them that they would be presenting their approaches to tackling various questions. When we share work in this format during math time, we refer to the group session as a Math Congress. So we similarly referred to this time as a Science Congress. The remainder of the day s science work time was spent working on the various group posters.

We spent the science period this day having the students share their discoveries about the tanks. The format we typically use for such a sharing session is to have all of the groups hang their posters on the front board. In this case, I emphasized with the groups that they needed to clearly indicate on their charts what questions or topic they were investigating. All of the class was assembled on the front rug and was then given an opportunity to look over all of the charts for a few minutes. Finally, students were asked to come to front and briefly discuss what types of investigations their group conducted and what discoveries were made. In some cases, a group had chosen one person to come speak on behalf of the group. However, in most cases, the entire group chose to come to the front and answer questions.

Throughout our work with the model, many students had been curious about the leaky landfill. It had come up as a topic for further inquiry, but I had told the class that it was something we would all be discussing in the coming weeks. For the introduction, I borrowed the idea presented in the video that accompanies the tanks. I started by asking the students what they thought a landfill was. The range of responses I got were the following:

• when water goes on land
• where garbage and pollution go
• a place where land is added from another spot
• a place where water is added
• there s one in Staten Island

At this point, we discussed the meaning of a landfill. Most students appeared to follow the explanation and asked some insightful follow-up questions.

We then conducted the experiment shown in the video. I soaked a paper towel in blue dyed water and then placed the paper towel in the back of a small Tonka toy dump truck. A student helped me demonstrated how the dump truck could drive the garbage to the landfill and dump it there. The dye in the towel was meant to demonstrate the contaminants in garbage. We placed the wet paper towel in the leaky landfill and brainstormed what we thought the effect might be on the tank. Students did feel that the dye would spread from the paper towel into the sand because they had noticed the holes in the landfill. We then left the tank to sit overnight. (At this point, there was no water flowing through the tank.)

The next morning, we sat as a class and discussed the observations we could make about the contaminants from the garbage (the blue dye). It had spread to form a small blue ring under the landfill. Many of the students proclaimed, That s not too bad. I thought it was going to move more. Another student then commented, Yeah, but that was just overnight. What would it do in a year? I allowed the students to discuss this for a while. Then I asked what might happen if water were added to the water source tank. This raised a variety of new questions for the kids. I said that, at this point, we were looking at the traveling of the contaminants as if there were no rain or snow in the area. What if there were? Would the pollution travel more quickly, less quickly, or at an equal rate. The class seemed to agree that the dye would travel more quickly in this case, because of the experience they had had seeing water pump the dye through the model. We added water to the tank and observed the effects over the next few hours. The water did indeed cause the dye to travel over to the lake, thereby getting into the wells. We had some further discussion about the implications for this in real life.

At the end of the science session the previous day, I had asked the students to think about what could be done to prevent the contaminants in a landfill from leaking into the soil. A few of the students had thought something could be done to seal the landfill. I left the students to think about this question overnight. When we began science on this ninth day of our work, we returned to this question. Students had many ideas about how best to seal the landfill. Some said that it could be lined with cement. Others thought netting could be placed at the bottom, before filling it with garbage. The netting would have fine, fine holes, they claimed, so water could pass through but not the contamination. This caused a flurry of comments because students started debating how that could be possible. Many said that the contaminants were inside the water, so there was no way one could be separated from the other. If the water passed through the holes, so would the pollution. In the opposite situation, though, students said the cement would not be practical because the liquid and rainwater that soaked into the landfill would have nowhere to go. It would bubble up out of the landfill, one of the students commented. So, the pollution would get into the ground anyway. The class was puzzled. A number of students wanted to do research on the Internet to see what actually happened with real landfills. I encouraged them to do this for the remainder of the science period. The other students were given the task of seeing what types of materials in the class would seal the landfill. If they were able to find workable materials, maybe some of these would give clues as to what was used in large-scale landfills. The students experimented with cheesecloth, Silly Putty, plastic bags, and various types of paper.

At the beginning of the science session we had a brief report out about our findings from the previous day s work. Students were interested in continuing their research, both online and with the model. I encouraged them to do this for the latter portion of science today, after sharing in a demonstration on the rug with the whole class. I placed a small piece of cheesecloth over the top portion of the soil between the landfill and the lake. I asked the class to imagine that this cloth represented crops being planted and that I was now going to nourish the crops with fertilizer. I placed a dropper full of blue died water above the crops and drizzled it over the cheesecloth. I then repeated this procedure filling the dropper three more times. The blue dye soaked through the cheesecloth and began to filter into the soil. As with the landfill, I again asked the students what they thought would happen when we returned to investigate the fertilizers the next morning. They predicted that the dye would travel, as it had from the landfill. One of the students commented that she thought it would be most realistic to add the water source, because crops are watered regularly if you want them to grow, so we d more closely be simulating the conditions. The class quickly agreed. So, the demonstration model was left to sit over night, while the students continued to work for the remainder of the afternoon in small groups, researching about groundwater and landfills online, creating sealants for the landfill, and returning to some of their previous questions from earlier work with the model. The following morning we checked in as a class to confirm our predictions that the fertilizers had indeed spread into the wells and lake. We had a discussion about the implications for this on our drinking water.