Q FE 430 – Watershed Processes Infiltration Lab (100 points) Statement of Purpose: In this exercise you will measure and report the infiltration capacity of soils in several locations available to you. Directions: Complete the experiment and lab report by Sunday of Week 4 at 11:59 PM. Submit your typed or scanned solutions in one of the following formats: .pdf, .doc, .docx to the ‘assignments’ area of Canvas. Include appropriate units with numerical solutions. See the section ‘What to turn in’ for more detailed instructions. Grading rubric is provided in separate document. Resources: Hewlett pgs. 59-62 & Hewlett review remainder of chapter 5 (pgs. 44--?65) Introduction: Two of the places where water is stored in forest ecosystems are the atmosphere, as water vapor, and in the soil, as liquid water. The process that transfers water from the atmosphere to the soil is precipitation. For precipitation to go from the atmosphere into the soil it must pass through the atmosphere/soil interface or the soil surface. The process that describes the flux of precipitation across the atmosphere/soil interface is called infiltration. At any given time, the rate that water passes through the soil surface is called the infiltration rate. The infiltration rate is not constant; it is variable and depends on the texture, density, porosity and moisture content of the soil. However, for a given location for a given soil type and density there is a soil moisture content for which the infiltration rate becomes a constant. That limiting infiltration rate becomes, in essence, a characteristic of the soil and it is called the infiltration capacity of the soil. The infiltration capacity of the soil can be used as an index of the impact of land use practices. Heavily disturbed and compacted soils will have a lower infiltration capacity than less disturbed and compacted soils. The change in infiltration capacity due to land management is not a part of this exercise. This exercise is dedicated to simply quantifying what the infiltration capacity of a site or a soil is. Equipment Needed: To carry out this exercise you will need to acquire some simple, basic equipment. The needed equipment is: • Ring infiltrometer • 6?inch plastic ruler • Container to carry and pour water with, and • Stopwatch. A picture of the needed equipment is shown below as Figure 1. The ring infiltrometer is, most likely, the most unique piece of equipment you will need and it is easy to fabricate. A ring infiltrometer is simply a hollow cylinder that is open at both ends. The one pictured is made of 3-inch aluminum pipe cut into 9? inch lengths and beveled at one end. Any hollow cylinder can be used. The most readily available material to use for a ring infiltrometer is a 16 oz can. Simply remove both ends from the can, wash it well, and remove any burrs that might be problematic and you have a ring infiltrometer. Realize that any size can or hollow cylinder will work for this exercise. It is just that 16 oz cans are readily available. A ring infiltrometer that is made out of a 16 oz can is pictured below (Figures 1 and 2). The ruler is used to measure the depth of the water in the ring infiltrometer. A felt tip marker, like a Sharpie, can be used to make a ring in the infiltrometer at 2 cm or 0.5 inches from the top and this will work if those constant measurements are used. A 6-inch plastic ruler will also work and is much more flexible in its use. Besides, they are only 69 cents and everyone can use a 6-inch straight edge. You will need a stopwatch to measure time to the nearest second. The most ubiquitous device that is currently easily available and can function as a stopwatch is a smart phone. I would recommend the smart phone because it can be used to take pictures of your ring infiltration installation to be turned in. Finally, you will need a source or fairly large reservoir of water, say a five gallon jug, and a smaller container to transfer the water from the large reservoir to the ring infiltrometer. The smaller container will be used to pour the water into the ring infiltrometer. Methods: You will use the above listed equipment to obtain an estimate of the infiltration capacity of a given site. So, first you must choose a location to measure infiltration capacity. If there is organic material or a duff layer at the chosen location, scrape that material off until you have cleared a small area of mineral soil. If the site is in perennial vegetation and it can’t be removed, like grass in a park or yard, then the infiltrometer will have to be installed on the vegetation. Once you have a small patch of mineral soil cleared, you should drive the ring infiltrometer into the soil up to about half of its depth. Make sure it is well seated. The best way to do this is to place a piece of wood (like a small length of 2x4) on the top of the infiltrometer and then tap on the wood with a hammer with sufficient force to drive it into the soil. [This is a trial and error exercise. You will not get it just right the first time. Keep trying until you are satisfied with the installation of the ring infiltrometer.] Once the ring infiltrometer is well seated in the soil, the 6-inch ruler can be placed in the top of the ring infiltrometer (see Figure 2 below). With the infiltrometer installed and the ruler placed in it, use the water container to fill the ring infiltrometer up to the very top. Start the stopwatch when the ring infiltrometer is filled to the top with water. The water will infiltrate into the soil and the water level in the infiltrometer will drop. When it has dropped 2 cm, stop the stopwatch and record the elapsed time it took for the 2 cm of water in infiltrate into the soil. Then, refill the infiltrometer back to the top and restart the stopwatch. This process should be repeated, measuring the elapsed time for the water to drop 2 cm, until the elapsed time between filling the infiltrometer becomes fairly constant. When the infiltration rate becomes fairly constant the elapsed times will be within several seconds of each other and the measurement can be stopped at that time. There are other possible outcomes that can be realized. One possible outcome is that the water level in the ring infiltrometer either doesn’t drop at all or it drops really slowly. If this occurs, let the measurement go for 20 or 30 minutes, record how much the water level did drop (i.e. 12 mm in 27 min) (thus the value of a ruler vs a fixed interval mark), record those data and then move on to the next measurement. A second possible outcome is that the water level drops very quickly, perhaps faster than the water can be replenished. The water level will drop 2 cm in 5, 10, or 15 seconds and it never shows a tendency to slow down. If this occurs, give it 20 or 25 readings, record all the data, end the measurement, and then move on to the next site. You should make nine estimates of infiltration capacity. Select three different locations to make infiltration measurements. Make these measurements in a forested environment if it is at all possible. Go out to a local forest (in Corvallis use the McDonald/Dunn Research Forest) and select three locations that are well separated from each other, for instance about 100 feet apart. If a local forest is not easily available, use whatever is available. If agricultural areas are available, use those. If you live in an urban or suburban setting, use what is available. You can sample garden plots, flower beds, or grass and lawns. At each of the three locations where you will estimate infiltration capacity, you should make three individual measurements. In other words at a location, measure infiltration capacity three times at three different sites all within about 1 meter of each other. This nested sampling scheme will yield small scale spatial variability as well as variability at a larger scale. So, make nine estimates of infiltration capacity; three measurements at each of three different locations. What to turn in: Write a concise lab report including the following items: 1. First of all, you need to describe the three locations you chose to collect infiltration data in. The description should include land use type (forest, agriculture, flower bed, lawn, etc.), soil type (if you know it), density (fluffy, loose, dense, compacted, etc), and soil moisture (dry, moist, wet, etc.). These descriptions can be qualitative. Take pictures of the infiltrometer installations (with your smart phone or camera) and include those with the descriptions. 2. Prepare an Appendix with all of your raw data in it. This means nine measurements worth of data. For each infiltration capacity measurement the raw data will consist of a list of values of the depth of water infiltrated associated with the elapsed time it took for that drop to occur. This section should include only the raw data. 3. It is necessary to turn the raw data into an infiltration capacity. You should turn in one example calculation that shows how you turned the raw data into an estimate of infiltration capacity. 4. To calculate an estimate of infiltration capacity with your data, use the values of elapsed time when that rate becomes steady at the end of the measurement. When the elapsed times become pretty uniform, use the last three observations you recorded. Turn the three observations of elapsed time into one average elapsed time. Convert the raw data of an infiltration interval (i.e. 2 cm) and an elapsed time (i.e. 5 min 37 sec) into an infiltration rate in cm/hr. By definition this becomes the infiltration capacity. You should end up with nine estimates of infiltration capacity, three groups of three observations. (See the attached page for example data and example calculations.) Address the following questions. 5. What is the average infiltration capacity for each of the three locations you sampled? Is this higher or lower that you expected? Explain your answer. 6. What is the large scale variability or what is the variability between the average values for the three locations you sampled? Standard deviation? Coefficient of variability? Is this what you expected? Explain and justify your answer. 7. What is the small scale variability? What is the variability in the three values that were measured at each location? Standard deviation? Coefficient of variability? Is this what you expected? Explain and justify your answer. 8. Take some time to figure out what normal and extreme rainfall intensities are for your locations. Are the infiltration capacities larger or smaller than the infiltrations capacities? Is this what you expected? Explain and justify your answer. Example Data: Measurement 2B: This was the second measurement taken in the family garden plot between the rows of bush beams. The soil is a nice silty loam (if you can estimate textures, do it), it is loose and friable and can be easily manipulated by hand. The soil is moist. (Add a picture of the site with your ring infiltrometer if you can.) Data: Interval Elapsed Time Interval time 2cm 54 sec 54 sec 2cm 2 min 30 sec 96 sec 2 cm 4 min 10 sec 100 sec 2 cm 5 min 48 sec 98 sec 2 cm 7 min 24 sec 96 sec 2 cm 9 min 6 sec 102 sec 2 cm 10 min 52 sec 106 sec 2 cm 12 min 38 sec 106 sec 2 cm 14 min 17 sec 99 sec Use the last three observations for the estimate of infiltration capacity: (106 + 106 + 99)/3 = 103.7 sec Thus, 2 cm of water infiltrated in an average of 103.7sec ((2 cm)/ 103.7 sec)(60 sec/min)(60 min/hr) = 69.4 cm/hr Infiltration capacity for the measurement is ?69 cm/hr ? (27 in/hr) Figure 1: The necessary equipment for this exercise. Two ring infiltrometers are pictured. The one in the back is the 3--?inch diameter, 9--?inch long aluminum tube used for the on--?campus course. The one in front is the homemade, 16 oz can ring infiltrometer. Also included in the picture are the 6--?inch ruler, a stopwatch, a water container, a wood block and a hammer. This equipment will allow completion of this exercise. Figure 2: The homemade, 16 oz can, ring infiltrometer installed in a raised bed ready for water with the ruler placed in the ring. Grading Rubric for Lab Short Report (100 points) You will turn in a short report in the form of a scientific journal article describing the assigned portion of the laboratory experiment. Instructions for how to write a scientific paper are below. The report should be 2--?3 pages of double--? spaced text in 12 point font. Graphs, photos, and appendices are not included in this page limit. Break up your paper into the following sections (include a heading for each section): 1. Title: the title should describe the topic of the report concisely 2. Objectives 3. Methods 4. Results: it should include at least one graph or table. 5. Discussion 6. Conclusions Rubric: 1. Title (5 points) • Title that concisely describes the topic of the report 2. Objectives (10 points) • Effectively presents the objectives and purpose of the lab 3. Methods (15 points) • Give a brief summary of the experimental methods used and what you measured to help answer your question. • Describe the three locations, including photos. • Provide enough details to allow for replication of procedure. 4. Data Calculations and Results (25 points) • Show raw data collected in Appendix, not in body of report. • Show any calculations or example calculations needed to analyze data. • Summarize trends of infiltration capacity in table or graph. Reference graphs or tables in text. • Accurately analyze data for lab findings, not any interpretation of them. • Whenever reporting measurements, include units. 5. Discussion and Conclusions (25 points) • Open with an explanation of how findings link to the context of lab. • Address questions & issues related to the lab & discuss the answers. • Sufficiently address other issues pertinent to lab. • Convincingly describe what has been learned in the lab. 6. Graph and/or table (10 points) • Make at least one graph or table with the data from this experiment. • The graph/table needs to be labeled with a figure or table number and a title to refer to it in the text. A figure or table caption includes enough information to tell the reader what they are viewing. • Label axes including units. • Do not turn in a graph with the gray background screen. • Do not turn in a graph that has a ‘Series 1’ legend if you have one variable. • If you have multiple variables in the legend, label them. No Series 1, Series 2, etc. Label the x--? and y--? axis and include the units. • Make sure there is a title for the graph. • For presentations and web material – use color. • For material that you hand in that may be photocopied and especially if it is simple – use black and white. • Differentiate data with different markers and/or line styles and weights. • Understand when to connect data points and when not to connect points. • Use a smoothed line sparingly and with caution. 7. Presentation and Overall Aims of Lab (10 points) • Format of tables and figures is correct. • Report is written in scientific style: clear and to the point. • Grammar and spelling are correct. • Demonstrates has successfully learned what the lab is designed to teach . Tips: Here are several examples detailing the correct way to write figure captions. There are many other examples available on the internet. Please ask the writing center or the instructor if you have any questions. https://www.e-education.psu.edu/styleforstudents/c4_p12.html When writing scientific papers try to write in the past tense. Try to remove personal forms of expression. For example instead of saying “ I found the distance to mars to be…” you would write “ The distance to mars was found to be….” Scientific and technical writing is meant to be brief and to the point. Avoid words expressing “feelings” about results; rather state what was found.