Precipitation samples from two rain collectors and one dry deposition collector are analyzed for nutrient concentrations and fluxes calculated using amount of precipitation inputs during that period. The rain collector at the low elevation administrative site (RCADMN) was established in 1968 in conjunction with stream water chemistry measurements at Andrews WS 9 (control) and WS 10 (clearcut), and also used in conjunction with WS1 (clearcut) and WS2 (control). The rain and dry deposition collectors at the Hi-15 mid-elevation site (positioned mid-slope WS 7) are paired with the HI-15 small watershed study including streamflow nutrient concentration and outflows on WS 8 (control), WS 6 (clearcut), and WS7 (shelterwood cut). Dry deposition samples were discontinued after after WY 2013. The original HI-15 rain collector (RCHI15) was established mid-slope WS 6 in 1969 and replaced with an NADP-style collector in 1988, which separates precipitation collection (RCHIR7) and dry deposition collection (RCHID7). Beginning 1 October 2013 the NADP-style collector was removed and a bulk collection sample initiated (RCHIF7) at the same site in the Hi-15.
Precipitation chemistry is sampled at a low elevation site (RCADMN at Primet, 430m) and a mid-elevation site (RCHIR7 in WS 7, 999m). Samples are stored in polyethylene containers until analysis. Prior to 1988, samples from both sites were collected every 3 weeks and transported to the Corvallis lab (CCAL) for analysis. Beginning October, 1988, samples are collected weekly and refrigerated at the Andrews. Precipitation samples are transported to Corvallis every 3-weeks, and weekly samples are analyzed individually. Beginning April 22, 2008, weekly samples are combined into a single composite sample and analyzed every 3 weeks similarly to the streamflow chemistry samples (CF002). Due to limited resources, winter-time, cold-weather samples (Nov-Mar) are only collected every 3 weeks, however, from April-Oct samples are still collected weekly and refrigerated.
Originally, collectors at both sites were open orifice (Polyethylene carboy jug with funnel). At the H. J. Andrews administrative low elevation site (RCADMN), precipitation was collected at the top of a 55 ft tower located in a clearcut. Water was stored in a polyethylene container inside an insulated shelter at the tower base. On January 20, 1982, the collector was moved to a 5 ft platform within 10 meters of the original location, and the polyethylene container is stored in an uninsulated bucket on the platform. At the mid-elevation site (RCHI15) precipitation was collected at the top of a 10 ft pole located in a clearcut near the top of Watershed #6. Water was stored in a polyethylene container inside an insulated shelter at the base of the pole. In October, 1988, a new collection site (RCHIR7) was started in a shelterwood with subsequent overstory removal near the top of Watershed # 7. An NADP-type wet/dry deposition sampler mounted on top of a 5 ft tower was used instead of the open orifice samplers used at the original site. The water is stored in polyethylene containers inside an uninsulated housing on top of the sampler. The "dry" side (RCHID7) container is collected and analyzed 2-4 times per year. The replacement collector (RCHIR7) and the original collector (RCHI15) at these mid-elevation sites were collected and analyzed concurrently for 9 weeks before the old site was discontinued.
Total precipitation from the Climatic Station WS#2 (CS2MET) by collection period was used in conjunction with nutrient analyses from the low elevation rain collector (RCADMN) to determine nutrient influx until 10/01/2002. Beginning with WY 2003 (10/01/2002), total precipitation from the Primary Meteorological Station (PRIMET) is used in conjunction with RCADMN. Total precipitation from the Hi-15 Meteorological Station (H15MET) by collection period is used in conjunction with nutrient analyses from the mid elevation rain collectors, originally RCHI15 and currently RCHIR7, to determine nutrient influx. Beginning with WY 2014 (1 Oct 2013), the NADP-style collector was dismantled and removed due to problematic operation. Dry deposition samples at this site were discontinued. Precipitation collection continues with an open orifice style collector (RCHIF7), which is located where the RCHIR7 NADP-style collector had been.
Assigning sample type codes (TYPE) is described here. Beginning Oct 1988, samples are collected weekly for analysis, and all samples are assigned sample type codes. A sample that is the result of precipitation collected continuously over the entire weekly period is considered a complete or full sample (TYPE="F"). Operational or other problems causing an incomplete or partial sample over the weekly period are coded as partial (TYPE="P"). Examples might include the malfunction of the sample lid on the NADP collector or possibly a collector overflow. Should zero precipitation result in no sample being collected for any week, sample type is no sample (TYPE='N'). Beginning 2007, there has been infrequent use of a sample type 'Biased' (TYPE='B'), which represents a wet collector sample that has had dry deposition input due to a faulty lid that is stuck open. Beginning April 22, 2008, samples are only analyzed every 3 weeks. If any of the weekly samples are partial or missing, the 3-week composite sample will be labeled sample type partial (TYPE='P').
Before Dec 1988, samples were collected on a 3-week basis. Successful operation of the collector over the 3 week period represents a complete or full (TYPE="F") sample. When the collector failed or was out of operation for any part of the 3 week period, the sample is designated as partial (TYPE="P"). When samples contained insufficient water for analysis, they were saved (TYPE='S') and combined (TYPE="C") with the following sample for analysis. Multiple samples might be saved and combined. In these cases the concentration data (Entity 1) and the flux data (entity 2) show precipitation for this entire period, and the "C"ombined sample's analytical measurements represent the entire period over which samples were saved.
Date and times listed as data_time in the data files refer to the end date of a collection period. Data is summarized by water year: October 1 to September 30. To allow summarization by water year, an artificial end-of-year sample point (TYPE="YE") is inserted on Sept 30 every year (Entity 2 flux data only) but is not an actual sample . Nutrient concentrations from the next analyzed sample (in October) are used with the precipitation total ending Sep 30 , the end of the wateryear, to calculate flux for this interval, which is designated TYPE="YE". Similarly, the flux value for this first sample of the new wateryear in October is calculated based on concentration values from the first October sample and on precipitation beginning Oct 1.
Laboratory procedures: Official compilation of water analyses begins with the WY 1969 (10/1/1968). Originally, samples are analyzed for suspended sediment, alkalinity, pH, ammonia nitrogen, nitrate, nitrite, dissolved kjeldahl nitrogen, ortho (reactive soluble) and total dissolved phosphorus, sodium, potassium, calcium, magnesium, and silica. Sulfate was determined for WY 1972 and sulfate and chloride in WY 1979. Sulphur and Chloride were analyzed at the University of Washington beginning 1988 until 2004, and are now conducted by CCAL at Oregon State. Analysis of specific conductivity was added in Dec 1974 and total P on an unfiltered samples in Oct 1974. Analysis of total kjeldahl N on an unfiltered sample was started in June 1978. Total N is calculated from the total Kjeldahl and NO3-N until May 2005. Direct analytical measurement of Total dissolved N and Total N (unfiltered sample) begins in May 2005. Dissolved organic carbon analytical measurement begins in 2003. Aluminum, iron, manganese, and nitrite were below levels of detection and were subsequently dropped from analysis. In general, duplicates were run on all analyses until Oct 1983, and are currently conducted randomly.
Other notes on analyses: 1) Since dry deposition analyses were initiated in 1989, 250 ml of dionized water are added to the dry deposition samples before analyses. 2) From 1969 - 1973 samples were analyzed for free ammonia (FNH3) prior to being digested for total nitrogen (DON). The FNH3 was driven off and collected and analyzed separately. Then the sample was digested and analyzed for DON. For these years TKN represents the sum of DON and FNH3. Listed Total Kjeldahl N (TKN) values from 6/1/1970-6/21/1971 for RCADMN do not include free ammonia (NH3-N) and are shown as estimated. 3) A combination of factors cause the results for silica prior to 17 March 1983 to be labeled as "Q"uestionable. Historic records indicate that many, if not all, of the samples prior to that date were frozen prior to analysis for silica. Freezing samples prior to analysis for silica will reduce the final analyzed concentration of reactive silica (the form we have historically determined). Another complicating factor is that the methodology changed about this same time. Until 1982, a stannous chloride method was used to determine silica, and this method is more prone to variability due to reagent instability.
Until May 2005, the CCAL lab analyzed for total dissolved Kjeldahl nitrogen (TKN) and also for total Kjeldahl nitrogen (UTKN), which is performed using an unfiltered sample and includes any particulates (sediment, biota) present. All dissolved results exclude particulates of 0.7 microns or greater. TKN includes NH3-N, but does not include NO3-N. The following are mathematically calculated in the data set and coded as 'D' when this occurs:
Dissolved organic nitrogen (DON) = TKN - NH3N
Total dissolved nitrogen (TDN) = TKN + NO3N (directly analyzed after May 2005)
Total nitrogen (UTN) = UTKN + NO3N (directly analyzed after May 2005)
Particulate nitrogen (PARTN) = UTKN-TKN, or UTN-TDN (after May 2005)
Particulate phosphorous (PARTP) = UTP - TDP
Currently, all samples are filtered upon arrival at the Corvallis lab (CCAL) and pH, alkalinity, conductivity, and autoanalyzer runs (NO3-N, NH4-N, SI) are made immediately. All analyses are completed within 6 weeks. Generally, samples are stored at 0 degrees C if not analyzed immediately. In the first year of sample collection (1968-1969), water was stored at 0 degrees C until operation of the PNW-1653 local lab in spring, 1969.
Generally, there is much greater trust and consistency to analytical measurements beginning in 1983.
Citations for all Cooperative Chemical Analytical Lab (CCAL) procedures:
APHA 2005. Standard Methods for the Examination of Water and Wastewater; 21st Edition; American Public Health Association, Washington, D.C.
EPA U.S. EPA Office of Solid Waste (OSW) Methods Team
APHA 4500-P B; APHA 4500-P E; EPA 365.2. Modifications: microwave digestion 60 minutes, 50 ml analysis volume, Ascorbic acid method.
The laboratory has automated the method used for analysis of total phosphorus (total phosphorus for unfiltered samples and total dissolved phosphorus for filtered samples) as of 16 June 2010. Samples submitted to the laboratory will now be analyzed using the Technicon Auto-Analyzer II (the same instrument used for analysis of nitrate, ammonia, phosphate, silica and total nitrogen). We have discontinued the routine use of the manual method using the Milton-Roy 601 spectrophotometer at this time.
We ran the manual method through the end of calendar year 2010 in an attempt to run comparisons for projects with historic results from the manual method. Results indicate there is expectation for reduced UTP/TDP due to the analytical change.
A Visual Foxpro program (pio_true) combines nutrient concentration data with precipitation to produce outputs in kilogram per hectare by water year (Entity 2), and creates annual nutrient concentrations (Entity 3). This program replaces the original PIO99 Fortran program in March 2005.
Precipitation values are obtained from both CS2MET (before WY2003) and PRIMET (beginning WY 2003) for the RCADMN rain collector. Precipitation values are obtained from both H15MET (before WY2006) and CENMET (beginning WY 2006) for the Hi-15 rain collectors (RCHI15, RCHIR7, and RCHIF7).
The Administrative Rain Collector represents nutrients inputs in conjunction with streamflow outputs for WS 1, 2, 3, 9, and 10, and is positioned among these stream gaging stations.
Watersheds 1, 2, 3: Though Watersheds 1, 2, and 3 are similar in terms of climate, geology, soils, and topography, they differ in average annual water yield. During the pre-harvest period 1953-1962, Watersheds 1 and 3 produced 86% and 88%, respectively, of the annual average streamflow produced by Watershed 2 (Rothacher et al 1967). From 1964 to 1992, Watershed 2 annual streamflow yield averaged 126 cm and ranged from 37 to 214 cm. Annual runoff: precipitation ratios averaged 0.56 and ranged from 0.28 to 0.71. Monthly runoff volumes follow closely the seasonal pattern of precipitation. Largest runoff volumes occur in December and January, and smallest in August and September. Typically, the largest peak flows occur during rain-on-snow events in which latent heat transfers melt shallow warm snowpacks, increasing water input to the soil by up to 25% (Harr 1981). Maximum rates of runoff during these events may exceed 80 percent of the average rate of precipitation for the preceding 12 to 24 hours (Rothacher et al 1967).
Watersheds 9 and 10: Prior to logging, vegetation on both watersheds consisted primarily of 450-year-old Douglas-fir mixed with hemlock and younger Douglas-fir. WS 9 left undisturbed as the control, 21 ac. WS 10 logged by skyline system to single landing, spring, summer 1975. WS 10 unburned, 25 acres. The Hi-15 Rain Collector represents nutrients inputs in conjunction with streamflow outputs for WS 6, 7, and 8 and is positioned on WS 7.
Watersheds 6, 7, and 8: The high-elevation watersheds also show differences in annual water yield. During the pre-harvest period 1964-1974, Watersheds 6 and 7 produced 113% and 79%, respectively, of the annual average streamflow produced by Watershed 8 (Harr et al 1982). From 1964 to 1992, Watershed 8 annual streamflow yield averaged 122 cm and ranged from 43 to 218 cm. Annual runoff: ppt ratios averaged 0.56 and ranged from 0.34 to 0.76. Monthly runoff volumes in the high-elevation watersheds follow the same pattern as observed in the lower-elevation watersheds. Snowpack in the high-elevation watersheds tends to be deeper, colder, and more persistant than in the lower watersheds. Contribution of snowmelt to streamflow may continue through June.
Detailed 1988 memo describing changes in the stream and precipitation sampling program. See http://andrewsforest.oregonstate.edur/data/studies/cf002/memo_H2Osampling_1988.pdf
A table showing the history of laboratory instrumentation for analytical measurements. See http://andrewsforest.oregonstate.edu/data/studies/cf002/CCAL_instrumentation_historic1.pdf
Silica data quality, 1969-1983. See http://andrewsforest.oregonstate.edu/data/studies/cf002/Historic_HJA_Silica_Data_Quality.pdf