On Monday, we again visited McCurdy High School to discuss water quality with Ms. Pepersack’s Biology class. We compared the Santa Cruz River and the McCurdy Acequia using our Vernier probes and the LaMotte kits. Again, we got very interesting results.
Why are the pH and conductivity values for this ditch so high? One important fact is that the ditch is no longer running, so this water has been sitting for a while. Perhaps salt from the sidewalks runs off into this water? This is our current working theory- let us know if you have any ideas!
Last night’s CoCoRaHS event was a great success, with 28 new rain gauges going to happy homes in northern New Mexico! We had quite a few Master Gardeners from Santa Fe present, with people from Rio Arriba, Taos, Santa Fe, and Los Alamos counties. Hopefully these new citizen scientists will get their gauges up before our next precipitation event!
If you missed last night but still want to participate in the CoCoRaHS network, it’s not too late! The network has online training videos located here, and our friends at Weather Your Way can sell you an official rain gauge here.
For the past two weeks, we’ve been working on water quality with Ms. Berryhill’s class of Earth Science students at McCurdy High School. McCurdy is located close to the Santa Cruz River, and it also has an acequia running through the campus, giving us two fantastic water sources in need of water quality testing!
While our River Classroom students are pros at water quality testing, this was the first time our McCurdy students have used our Vernier water quality sensors. In order to give the students some practice, we did a little experiment.
Students divided into five groups. Each was given a quart-sized mason jar. Students filled their jar about 3/4 of the way full using tap water. Each group used NMWC’s sensors (as well as LaMotte test kits for nitrates and phosphates) to evaluate the quality of their initial sample. We tested temperature, pH, dissolved oxygen, conductivity, turbidity, nitrates, and phosphates. Fortunately, the numbers were reasonable.
Next each group polluted their water, using chemicals that are generally poured down the drain or that run off into waterways. Each group used a different combination of plants, fertilizer, coffee grounds, oven cleaner, dish soap, shampoo, toothpaste, etc. Some of these products were “green”, while others made no claims to be healthy for the environment.
After creating some of the most foul-smelling water samples I’ve ever seen, students took more water quality readings (all recorded on a data sheet). Then they were given a daunting task- clean the water! Possible tools included 2 L bottles, coffee filters, socks, sand, rocks, and charcoal. As usual, students were given next to no direction from us. They had to figure it out. They also had to continue water quality testing along the way so that they could determine which filtering methods had the most impact.
While turbidity decreased as students continued to try to filter their samples, nobody ended up with water they wanted to drink. Conclusion: It’s much easier to keep water clean that it is to try to clean it. Filtering water takes time, energy, and resources, so let’s take care of the water we’ve got!
After we had plenty of practice with the water quality sensors, we moved on to measuring water from the Santa Cruz River and the McCurdy Acequia. During lunch, Ms. Berryhill and I took two grab samples from the Santa Cruz River. These field replicates were further divided into four total samples, one per group. Each group measured each parameter (including temperature and DO, although the official numbers were those that we recorded at the river).
After the Santa Cruz samples had been processed, students went outside to sample the acequia. Because we were running out of time, we only took one sample. Each group recorded their numbers on the board, leading to an excellent discussion of uncertainty in our measurements. If all four samples came from the same place at the same time, why did each group get slightly different numbers? Our uncertainty comes from sample handling, instrument sensitivity, and several other sources.
The comparison between the river and the acequia turned out to be much more interesting than we had suspected. Not surprisingly, the ditch had a much lower level of dissolved oxygen, a much higher pH, very high conductivity, and a higher temperature. The entire class agreed that the Santa Cruz River is a much healthier body of water!
Last week was very busy- we taught several classes. On Wednesday, River Classroom was back at New Mexico Wildlife Center for an Engineering Design Challenge! One of our goals for the class is to develop working wind turbines and water wheels that we can hook up to a generator. This really demonstrates how mechanical energy can be converted into electrical energy. In order to build these devices, we have to have a plan, and what better way to develop a plan than to let your class do the work?
The instructions we gave the students were simple and went something like this:
“Over on that table, we’ve provided you guys with a variety of materials. Take these and create a model of a wind turbine or a water wheel. You have until 1 pm. Go.”
Our students are very smart, and we knew that they could rise to our challenge- turning these random materials (plastic bottles, drinking straws, wooden dowels, pins, corks, and a variety of containers from the recycle bin) and creating a model of a wind turbine or water wheel that really works.
We recognize that not everybody likes to work in a group, so we let the students decide if they wanted to work individually. We also voted on the best number of people to have in each group so that everybody gets a chance to do something. Eventually we had 5 groups, with anywhere from 2 to 4 people per group.
Three groups worked on water wheels, while two groups constructed wind turbines. The range of designs was spectacular! Once again students were not required to have a finished blueprint before they began, but they did need to have an idea of what materials were needed.
As the activity progressed, students began testing their models, with varying degrees of success. Everybody had a few modifications at first.
As time progressed, the models improved and became more efficient.
It was a very cold day, so most of the initial tests took place inside.
Eventually some of the braver students ventured outside for further testing.
By the end of class, nearly every group had a working wind turbine or water wheel. Some designs worked better than others, which turned into a review of the concept of efficiency. As part of their reflections, students had to draw a detailed blueprint of their model.
The variety of designs that our students can come up with given very little instruction never ceases to amaze us.
After all of this engineering, a few groups demonstrated their water wheels for the class. Part of their reflection in their science notebook was to describe the types of energy used in their model and to list how energy was lost in the model (referring to our discussion of efficiency).
Here are a few excerpts:
“Kinetic: When the wind blows on the “wings”, they start to move.”
“Friction happens when the plate touches the cork and the spindle. I know because it causes heat.”
“Our water wheel uses mechanical and gravitational energy. When the stick is moved it creates mechanical energy. When the plate is filled with water gravity brings it down.”
We are looking forward to continuing work on these models and to building a real version in the next few months!