Reed College Canyon
An Exploration of some Chemical, Physical, and Biological Features of the Reed Canyon Reach of Crystal Springs Creek, Portland Oregon, in the Fall of 1995
Natural Science 110 class at Reed College, Fall 1995
Deb Breiter*, Tom Dunne*, Arthur Glasfeld*, Meredith Miller, Josh Filner, Steven Frantz, Randie Dalziel, Ingrid Loma, John McIntyre, Candace Schaffer, Elaine Shinn, Ell Spangenberg, Junryo Watanabe, and Students of the fall Semester 1995 Natural Science 110 Class
Contribution from the Department of Chemistry, Reed College, Portland, Oregon 97202-8199
The following article was produced by students and faculty in the Natural Science 110 class at Reed College, Fall 1995. Copyright ©1995 Reed College
This article is being published as a historical reference. Some information may no longer be current.
Abstract: Except for the determination of corridor width, streamwalk observations are consistent from group to group. Bulk flow rates at Picnic Area Bridge are not significantly different from the seasonal values of last year. The seasonal variation of bulk flow rates is found again this year and remains to be explained. Measurement of linear flow rates shows that surface water moves through the canyon significantly more rapidly than bulk water. A comprenhensive depth profile study for Reed Lake has been initiated. Observed variations in dissolved oxygen and temperature in Reed Lake can be understood in terms of plant decay and solar energy variations. Phosphate and nitrate concentration data are completely consistent with those measured last year and therefore again show a significant nitrate concentration drop from the top of the canyon to its bottom. Coliform bacteria concentrations are high in all canyon waters, which are therefore unsafe for human consumption. An attempt to simulate the heavy metal leaching of acid rain failed again, but several improvements on this simulation are possible. Measurements of pH of Canyon waters and rain water show a healthy condition of low acidity.
* Authors to whom inquiries should be addressed.
For a more complete introduction to this project the reader is referred to the report on last year's canyon laboratory available from any of the three designated authors of this year's report. As did last year's study, we made measurements in order to further characterize the canyon and in particular to illuminate the causes and effects of the increasing abundance of aquatic plants in the canyon in the period from May to October.
- The streamwalk investigations were done following the directions in the Environmental Protection Agency's Streamwalk Manual, revised July 1994. Latitude and Longitude assignment to the eight study sites were facilitated by a locally produced high definition map with latitude/longitude grid lines separated by one second of arc.
- Bulk flow rates were measured as described in the 1994 report, but at only one location this year, the Picnic Area Bridge. The Ritmanis Pond site was abandoned because it is now flooded as the result of beaver activity. The upper bridge site was abandoned because its complicated stream structures make measurement precision relatively difficult to achieve.
- Because it was suggested to us last year that for understanding the dynamics of surface plant growth we needed to know surface water flow rates we made the first attempt to do that by timing identifiable floating objects moving through a naturally "pegged out" 18.7 foot course in central Reed Lake just east of the high bridge. So that wind effects could be detected and eliminated as forces pushing our floating objects a wind speed meter (by SOU'WESTER-detects winds in excess of 5mph) was purchased from a nautical supply house. Wind speed measurements on the high bridge were made simultaneous with the floating object clockings.
- Dissolved oxygen, temperature and water depth measurements were made exactly as described in last year's report. Experimental raft locations were determined from the shore of Reed Lake by an instructor equipped with compass and the previously described latitude/longitude grid detail map.
- Phosphate, nitrate and coliform bacteria concentrations were determined exactly as described in last year's report.
- Trace concentrations of lanthanum were determined by the neutron activation procedure described in last year's report. In an attempt to gain greater reproducibility, all student groups were asked to draw their canyon sediments from a single bottle of dried, ground and sieved sediments.
- Measurement of pH was made using Corning Model 320 pH Meters.
Table 1. Streamwalk Observations Summary (9/18/95 to 10/6/95)
|Site #||Latitude||Longitude||Stream Depth
|Canopy % Mode|
|1||45028'56"N||122037'56"W||5± 3; 6||12.5± 3.1; 6||34± 15; 5||50-75;4/6|
|2||45028'56"N||122037'57"W||3.6± 1.1; 4||13.8± 1.7; 4||80± 60; 3||50-75;4/4|
|3||45028'55"N||122037'59"W||5± 2; 3||14± 5; 3||32± 15; 3||50-75;2/3|
|4||45028'55"N||122038'00"W||4.3± 1.0; 4||12± 6; 4||24± 21; 3||50-75;3/4|
|5||45028'55"N||122038'01"W||3.7± 0.6; 3||17.1± 2.2; 3||NM||0-25;2/3|
|6||45028'55"N||122038'02"W||6.3± 1.5; 3||10.9± 1.3; 3||52± 28; 2||50-75;1/3 Median|
|7||45028'55"N||122038'04"W||3.9± 0.6; 4||9.1± 0.9; 4||19± 6; 2||75-100;4/4|
|8||45028'55"N||122038'05"W||6.4± 2.7; 4||7.9± 1.3; 4||44± 27; 4||50-75;3/4|
Note: Sample size is indicated with each datum entry in Table 1.
Table 1 remarks: Site 1: Some garbage present; bed consists of sand, gravel and cobbles; Site 2: Notable lack of vegetation in Renn Fayre Glade, bed consists of sand gravel and cobbles; Site 4: Fish present, north stream corridor looks trampled; Site 5: Evidence of erosion under the theatre; Site 6: Woody debris in stream from an unnatural source; Site 8: High water clarity.
Summary of Flow Rate Results Measured at Picnic Area Bridge (Bulk Flow) and High Bridge (Linear Flow) in the period June 9, 1995 to July 14, 1995 (Bulk Flow Only) and in the Period September 18, 1995 to October 6, 1995.
Period June 9 to July 14:
- Average dry day bulk flow rate (sample size = 6): 3.0 ± 0.5 ft.3/s.
Period September 18 to October 6:
- Average bulk flow rate on days with less than 0.01 inches rainfall (sample size = 15): 11.0 ± 2.9 ft.3/s.
- Average linear flow rate on days with no more than 0.03 inches rainfall and no detectable wind (sample size = 3): 0.055 ± 0.026 ft./s.
Table2. Depth, Temperature and Dissolved Oxygen Concentration in Reed Lake, Fall 1995
|tS(°C)||[O2]S %Sat.||tD(°C);D(m)||[O2]D %Sat.|
|9/19||0.00||c||> 1.5||15.3||72||13.7; 1.50||69.2|
|9/25||0.31||j||> 1.5||15.8||80||13.0; 1.10||69.4|
|9/28 AM||0.16||o||2.90||13.9||62||13.5; 1.0||59.8|
|10/5 PM||0.00||y||1.70||13.1||100||11.8; 1.50||65.2|
|10/5 PM||0.00||z||3.08||13.4||65||nm; 1.50||70|
|10/6||0.03||b||> 2.0||13.0||84.5||12.1; 1.50||66.5|
Table 3. Average Ortho-Phosphate Concentrations in the Waters of Reed Canyon in the Period from October 9, 1995 to October 13, 1995 at Upper Bridge (UB) and Picnic Area Bridge (PAB)
|Date||Rainfall (in.)||UBAvg.Con.(mgP/L); N||PABAvg.Con(mgP/L); N|
|10/9||0.01||0.076 ± 0.007; 3||0.074 ± 0.009; 4|
|10/10||0.72||0.078 ± 0.010; 2||0.083 ± 0.015; 3|
|10/11||0.73||0.098 ± 0.023; 2||0.075 ± 0.010; 1|
|10/12 AM||0.01||0.08 ± 0.01; 1||0.082 ± 0.010; 2|
|10/12 PM||0.01||0.083 ± 0.015; 3||0.093 ± 0.006; 3|
|10/13||0.08 ± 0.01; 2||0.09 ± 0.01; 2|
Note: N stands for sample size in Table 3.
Table 4. Average Nitrate Concentrations in the Waters of Reed Canyon in the Period from October 9, 1995 to October 13 1995 at Upper Bridge (UB) and at Picnic Area Bridge (PAB)
|Date||Rainfall (in.)||UBAvg.Con(mgN/L); N||PABAvg.Con(mgN/L); N|
|10/9||0.01||5.8 ± 0.5; 3||5.5 ± 0.4; 3|
|10/10||0.72||5.8 ± 0.6; 2||5.3 ± 0.2; 2|
|10/11||0.73||5.5 ± 0.1; 2||4.17 ± 0.29; 3|
|10/12 AM||0.01||5.2 ± 0.1; 1||5.6 ± 1.1; 2|
|10/12 PM||0.01||6.00 ± 0.14; 3||4.73 ± 0.31; 3|
|10/13||0.00||5.7 ± 0.2; 2||5.1 ± 0.5; 2|
Note: N stands for sample size in Table 4.
Table 5. Average Coliform Bacteria Concentrations in the Waters of Reed Canyon in the Period October 23, 1995 to October 27, 1995 at Upper Bridge (UB) and Picnic Area Bridge (PAB)
|Date||Rainfall (in.)||Avg.UB Conc. (L-1); N||Avg. PAB Conc. (L-1); N|
|10/23||0.01||(2.8 ± 1.4) x 103; 6||(3.5 ± 1.3) x 103; 6|
|10/24||0.00||(2.5 ± 1.2) x 103; 5||(4.4 ± 2.8) x 103; 5|
|10/25||0.42||(3.5 ± 1.2) x 103; 4||(5.7 ± 2.6) x 103; 4|
|10/26 AM||0.07||nm||(7 ± 3) x 103; 2|
|10/26 PM||0.07||(3.2 ± 1.8) x 103; 4||(6.0 ± 3.0) x 103; 5|
|10/27||0.00||(1.1 ± 0.4) x 103; 2||(2.7 ± 0.6) x 103; 2|
Note: N stands for sample size in Table 5.
Summary Statement of the Results of Testing the Leaching of the Heavy Metal, Lanthanum, by Soaking Ground-Up Canyon Sediment with Waters of Variable Acidity.
For room temperature soaking times of up to four days no significant evidence was found for the reduction of lanthanum concentration in our sediments even for soaking solutions of the highest acidity (pH = 0.0).
The average pH of Canyon waters measured during the rainy week November 6 to November 10 was 7.0 ± O.4 (twenty two measurements). The average pH of rain in this week was 5.6 ± 0.8.
To our knowledge this streamwalk study is the most extensive test of the reproducibility of streamwalk observations. The reproducibility for three of the four stream parameters reported in Table 1 is reasonably good, we believe. It is only with the corridor width that reproducibility is relatively poor with standard deviations showing up that are often quite close in magnitude to their data. This situation is even worse than meets the eye here in that several groups did not even venture to guess the corridor width and some reported values were eliminated as unreasonable in writing up this report. Clearly the estimation of stream corridor width is an issue which must be critically addressed in the next revision of the Streamwalk Manual. Finally our streamwalk data indicates that our stream is relatively healthy and may be ready with a minimum of provision for the fish run planned to be initiated here in the near future.
Measured flow rates at Picnic Area Bridge show year to year consistency and seasonal variation consistency. Last year's class dry day average value was 7 ± 3 ft.3/s not significantly different from this year's dry day class average of 11.0 ± 2.9 ft.3/s. This year's class average was significantly different from the preceding summer's average value, 3.0 ± 0.5 ft.3/s as was the case last year. To round out the consistency we have last summer's average value (2.0 ± 0.4 ft.3/s )not being significantly different from this (1995) summer's average value. The cause of these seasonal variations remains a mystery. It would be interesting to measure flow rates throughout our dry season to see whether the flow gradually increases from summer to fall or whether the variation is jumpy.
If we assume that the volume of Reed lake is about one million cubic feet, then the average residency time for bulk water in the lake is about one day in the fall and three to four days in the early summer. Given the zero wind, dry day average linear surface flow rate of 0.055 ± 0.026 ft./s, if we assume that the length of an assumed rectangular Reed Lake is about 1400 feet, then the average residency time for surface water in the fall of 1995 in Reed Lake was about seven hours. Any plant life keeping up with this flow would have a very short lifespan in the lake. This, however, may not be an accurate model, if the floating plant life becomes embedded in the lake.
Looking at Table 2 and the accompanying map on Page 5(a) reveals several trends. First, depth generally increases on going from east to west in Reed Lake. This is surely mainly the result of the dredging out of a swiming hole at the east end of the lake on the first Canyon Day in 1915. Second and third, both temperature and oxygen concentration quite generally decrease with depth. The cause of the first is presumably diminished sunlight, and the latter, we guess, is evidence for oxygen loss by its being used up by dead plant decay reactions, a condition which should become more extreme as surface plant growth becomes more extreme. Two other modest trends with obvious causes: Surface waters are colder in the morning than in the afternoon and surface water gets colder as the fall season progresses.
Looking at Table 3 and taking 10/9, 10/12 PM and 10/13 to be dry days we get the following dry day average values for phosphate concentration: At UB we have 0.080 ± 0.003 mgP/L and at PAB we have 0.086 ± 0.010 mgP/L. Neither of these are significantly different from each other, nor are they significantly different from last year's values at these respective locations, 0.092 ± 0.016 mgP/L; 0.075 ± 0.010 mgP/L.
Looking at Table 4 we do the same kind of dry day averaging that we did above. At UB we get 5.83 ± 0.15 mgN/L and at PAB, 5.11 ± 0.39 mgN/L. These values are significantly different. Last year's values at these locations, also significantly different from each other, were, respectively, 5.93 ± 0.28 mgN/L and 4.68 ± 0.07 mgN/L. At each location the value from last year is not significantly different from this year's average value. This chemical variation in going from the top of the canyon to the bottom seems to be real. Why doesn't this variation also show up with the phosphate concentrations? Possibly because the phosphate data is too imprecise to reveal such a trend. The cause of this trend is a mystery. It is possible that lower canyon waters sample deeper less "urbanized" ( with gardener's nitrate fertilizers) water. The good news in the phosphate and nitrate data is that canyon waters are not experiencing a rapid growth in these plant nutrients.
Of course, the bad news is that that momentarily leaves us without an explanation of what is causing our remarkable plant growth condition. It is possible that reduced summer water flow may be at least partially responsible for this.
The coliform bacteria concentrations are similar to those from last year on days of comparable rainfall. The drinking water standard, 100 L-1 is hugely exceeded at all locations and at all times.
Suggested further improvements for the acid rain soaking simulation: 1. Increase sendiment particle reactivity with acid by making the particles smaller. 2. Use soaking times much longer than four days. 3. Measure the heavy metal that is lost rather than that which remains behind in the sediment. 4. Soak at somewhat elevated temperatures.
The pH measurements of canyon waters show a healthy condition of neutrality expected for the hard water of the canyon where the high carbonate content (see 1994 Canyon Laboratory Report) would be expected to protect the waters from acidification by rain water. In fact, the pH of our rain water is presently high enough for us to say that we do not have an acid rain condition here, so the Canyon water's potential for protection against acid rain is not presently needed.