Evaporation at Western Pond

This topic submitted by James Boukalik, Sean Collins, Alec Risch, Drew Vankat (collins1@po.muohio.edu) at 10:32 pm on 12/9/99. Additions were last made on Thursday, February 8, 2001. Section: Cummins

Abstract
Our project is a study of the evaporation rate of water from Western Pond. The project includes laboratory tests of variables that affect evaporation i.e. wind, air temperature, environment, and surface area. The tests are designed to determine what conditions increase the evaporation rate of water. The ultimate goal of this project is to pinpoint variables that affect evaporation, and apply the findings in real life. The results and conclusions of this study will prove the role of evaporation in the life of Western Pond, and the contribution of evaporation to the water cycle.
I. Introduction
Western Pond is a central feature of Western Campus. The pond fulfills it role as a place for students to meditate, and enjoy. What else does the pond contribute, not just to this campus, but also the greater environment? More specifically, how does this tiny pond, in the middle of Western Campus in Oxford, OH, affect the world at large? The purpose of this project is to test specific variables that might have some effect on the evaporation rate of water, and in the end, determine how much Western Pond contributes the water cycle.
Variables include air temperature, wind, environment and surface area. Two types of tests were utilized in this project: field tests and laboratory tests. The field test was designed to test the effects of air temperature and environment on the evaporation rate. The different environments include woods and open areas. Previous instruction indicates that warmer air temperatures should increase evaporation. Since solar radiation affects evaporation, it can be hypothesized that, in an open environment, evaporation will be greater. In the lab were the controls, and tests for surface area and wind. Hypotheses for tests in the lab, according to research, are that wind and a greater surface area increase evaporation rates.
II. Relevance
We have read several science journal articles that deal with evaporation from varying experimental angles. A Sweden-based engineering firm studied methods for hazardous waste disposal involving evaporation (Filtration & Separation p.429). Some scientists have studied evaporation rates in different types of soils (Soil Science Society of America Journal pp.341-346). Other studies have been done that determine that greater surface area increases evaporation yields (Solar Energy pp.261-266). A group of scientists has found evidence that evaporation acts as a cooling method for bodies of water, much like the act of sweating cools the human body (Science News p.69). Winds hinder rainfall, and push evaporated moisture out of areas that need water (Natural History p.48-49). According to Dr. Klink of Miami University, wind could be a great factor in the evaporation rate. By moving clouds, wind can increase or reduce solar radiation, directly affecting evaporation. In a study of evaporation in oat and rye crop fields, scientists determined that there is seasonal difference in evaporation rates (Journal of Soil and Water Conservation pp.263-268). Two interesting studies dealt with deforestation in tropical environments. Levels of forestation clearly are important in regards to evaporation (World Development pp. 53-65) & (Ecological Economics pp.107-123). In a related study, a group tried to calculate the levels of evaporation in fields that have been slashed and burned for agriculture (Journal of Hydrology pp. 293-305). Another study calculated the evaporation over a 44-day period from the forest floor (Journal of Hydrology pp. 97-113). Salinity is also a factor we are interested in testing. An article in Compton's Electronic Encyclopedia describes the way in which salt is extracted from water by evaporation. The encyclopedia also states that salt raises the temperature of water. That is why salt is put on icy roads in the winter. Since salt increases temperature, it would also increase the evaporation rate of water. All of these studies are related to evaporation and its effects on the natural world.
All of these studies' results can be implemented in the real world. We can take their data and convert it to many aspects of society. Hazardous waste can be disposed of more efficiently and effectively. Farmers can tell how much water they should expect to lose from their soils due to evaporation. Companies like fish hatcheries or water treatment plants can determine evaporation rates of different-sized tanks and basins. Perhaps in the future we will use evaporation to cool off things such as houses or cars. Even seasonal evaporation numbers can be important to companies, which are looking at locating in certain areas of the country or world.
According to Professor Cummins, evaporation studies are relevant in various fields. For example, rain forests rely heavily on evaporation. Land that has been cleared of forests is extremely dry. Solar radiation beats down, drying the ground out. The canopy of the rain forest acts as a greenhouse, trapping moisture that evaporates from the forest floor. The trapping effect regulates general humidity and temperature.
III. A. Materials and Methods (our group study)
The proposed set-up of the project is to place ten evaporation pans at varying locations around Western Pond. Five pans will be placed in open spaces, five in wooded spaces. Daily, beginning on Oct. 4, 1999 and continuing through Nov. 22, 1999, we will measure the water level in the pans. Any loss or gain will be attributed to evaporation or the water cycle (rain). We will also place three temperature probes; one in an open area, one in the woods, and one in the classroom. In addition to these observations, Professor John Klink will provide us with daily air temperature readings taken from the Oxford area. Our group will also be making observations from five control pans located in Boyd Hall. We plan to record the same sets of data from these pans. We will test other variables in our control set-up. For two weeks we will measure evaporation in the classroom in Boyd. For two weeks, the effect of wind on evaporation will be tested with a set-up including fans. The remaining two weeks will be spent measuring evaporation rates in pans of greater surface area.
Combining these sets of observations we hope to estimate evaporation rates of Western Pond in different conditions. Our experiments will be statistically sound because of the frequency of data collections, and number of variables accounted for. Dr. Cummins suggested the number of pans that should be used in the project. There are enough pans set up in various places around the pond to give accurate samples from all possible environments. The use of control pans helps us compare unstable to stable environments.
Materials used in our study will be pans of two different sizes to house the water, chicken wire to cover the pans from foul play (swans, people, etc), and digital temperature probes to record temperatures. A small floor fan will be used to simulate wind in the lab.
III. B. Materials and Methods (class lab)
For the in-class lab there will be fifteen pans in Boyd Hall simulating different conditions. These pans will be set up as follows: three control pans (room water temperature, no wind), three pans (room water temperature, with wind), three pans (outside), three pans (with salt), and three pans (larger surface area than control pan, room water temperature, no wind). 24 hours prior to the lab, measurements will be taken on all of the pans. The day of the lab the initial measurements will be disclosed to the class. The class will then be asked to hypothesize which variables will have which effects on the rate of evaporation. Each lab group will measure each of the pans. They will measure the current water level, and sharing this with the rest of the class, come together and make conclusions about their data.
The class is not directly involved in the group study, but this lab should give them a better understanding of the project. After this lab they should be able to name factors that affect water evaporation, and which ones have the most effect. The relevance of the project will be more evident to the class following the lab.
IV. Results

Due to the sheer number of data collected during the forty-nine days, statistics and how they are interpreted is the key to making sense of our results. As a result, Statview and its various applications were of vital importance to helping us understand our results. For nearly every variable involved in the experiment, a t-test was performed to determine whether that variable accounted for a significant difference in the evaporation rate. In each case, a comparative graph was prepared by Statview to indicate changing trends throughout the length of the experiment in evaporation. In addition to analyzing the results based on separate variables, we also looked at the larger picture to determine how this relates to evaporation in Western Pond. Furthermore, we were able to take the temperature findings and display them in average daily temperature so that the information would make more sense to us. All of these combined statistics form the basis of our understanding of the results.
Display of our results can be complicated due to the great number of variables and pans. As a result, graphs that chart overall trends in evaporation are most effective in helping us to understand what has happened. The raw material was recorded in Statview in various tables and charts. On the surface, the material seems to be simply a jumble of unrelated data, however it can be easily understood with some synthesis and some use of graphs. The data is easily understood when it is displayed properly.
V. Discussion
Our results showed us many things. In most instances there was a significant difference in the data between two or more variables. This was not surprising, as it agreed with our hypothesis, but there were other instances where the results went against what we had predicted.
Going through the different criteria and variables, here are the results:
1. This graph compares water loss in milliliters among pans in three specific environments. According to our data, the control pans inside lost the most water, followed by the open outside pans. The pans in the woods lost the least amount of water. The comparisons of woods versus the inside, and open versus the inside have p-values of .0001. Therefore, there is a significant difference in those two comparisons. Woods versus the open had a p-value of .5958. There is not a significant difference. This could mean one of two things. The environments of woods and open may not have varied enough to make a difference, or environment may not have the effect on evaporation that we had hypothesized.
2. In the graph comparing lab tests, controls, and outside experiments, the data suggests that wind has a significant effect on evaporation. A p-value of .0001 rejects the null hypothesis, meaning that the environments and conditions of the set-ups were significantly different.
3. Graph number three disproves our hypothesis that warmer temperatures increase evaporation. The p-value of .4719 proves that there is not a significant difference in temperature throughout the study. However, due to some experimental difficulties, we feel that it is still possible that warmer temperatures produce more evaporation. It could be that there were more relatively cold days that warm or hot ones. That would mean more total water loss for the cold days, hence the appearance of the graph.
4. According to graph four, surface area plays a part in evaporation rates. Our hypothesis was correct that larger surface area increases evaporation. A p-value of .0001 suggests that the pan sizes were indeed significantly different.
5. Graph five compares water loss under two conditions. It tells us, during the three seasons, among the three locations, the inside pans still lost more water, followed again by the pans in the open. The p-values of .0001 suggest that there is a significant difference between inside and outside pans, but not between wooded and open pans.
6. We do not have a graph comparing water loss during the different seasons under different conditions, but the p-value of .0001 suggests that there is a significant difference between the average temperatures. There is no graph because there was too much information for the program to process.
From our data we were able to determine how much water was lost from Western Pond. We added up our combined water loss, and split them into two categories. The first is for the first twenty-one days when we had five pans around the pond. The second category is for the last twenty-eight days when we had ten pans around the pond. We then set up one ratio for each category. The ratio is the total water loss from pans over the estimated square meters of all of the pans equals 'x' liters lost from the pond over estimated square meters of the pond. Look at the ratios below.

1st twenty-one days
4.563 L/ .19 m^2 = x liters/2100m^2. x = 50,433 L
Last twenty-eight days
10.575 L/ .38m^2 = x liters/2100m^2. x = 59,441 L
Combined estimated loss from pond
108,844 L.
We believe this number to be accurate, because we were able to estimate an amount for a rectangle in the middle of the pond to be around 600,000 L. Look below.
Middle rectangle is 2667cm x 1219.2 cm x 182.88 cm. This is a volume of 594,653,778.432 cm^3. 1 cm^3 = 1 ml. So it is approximately 600,000 L.
For future investigations, it would be interesting to note evaporation rates in more extreme environments. The environments within our study were possibly too similar to register a significant difference, but this may change with environments that are more unique. After our experiment, we are still curious about the effect of temperature on evaporation rate. It still seems logical to us that higher temperatures would yield higher evaporation rates, and indeed our research pointed to that result. Therefore, for future investigation, a more extensive look at different evaporation rates for differing temperatures would be beneficial. Furthermore, the effect of salt and salinity on evaporation would be interesting to observe. Changes of salinity within the water may effect changes in evaporation rates.
According to our study, evaporation rates are affected by various factors. Some of our hypotheses were proven to be true by our data while others were not proven. As a result, there is definitely room for further investigation on this topic.

Cited Works

"A Drought's Unyielding Cycle", by Kenneth Kunkel; Natural History Jan. 1989 pp 48-49
"Do Clouds Provide a Greenhouse Thermostat?" Science News Aug. 1 1992 p.69
"Evaporation from young secondary vegetation in eastern Amazonia", by D. Holscher, T.D. de A. Sa, T.X. Bastos, M. Denich, and H. Folster; Journal of Hydrology volume 193 1997 pp. 293-305
"Forest floor evaporation in a dense Douglas fir stand", by M.G. Schaap and W. Bouten; Journal of Hydrology June 1997 pp. 97-113
"Spatial Variability of Evaporation along Two Transects of a Bare Soil" by R.J. Lascano and J.L. Hatfield; Soil Science Society of America Journal March 1992 pp. 341-346
"Surface energy balance partitioning over rye and oats cover crops in central Iowa" by J.H. Prueger, J.L. Hatfield and T.J. Sauer; Journal of Soil and Water Conservation Third Quarter 1998 pp. 263-268
"The Paths to Rain Forest Destruction: Crossnational Patterns of Tropical Deforestation" by Tom Rudel and Jill Roper; World Development Jan. 1997 pp.53-65
"Third-world debt and deforestation", by James Kahn and Judith McDonald; Ecological Economics Feb. 1995 pp. 107-123
"Waste Not Want Not - With the Help of Evaporation" Filtration and Separation June 1997 pp. 425-429
"How Water Evaporates and Boils." Compton's Electronic Encyclopedia

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