Stream chemistry data
STREAM CHEMISTRY METADATA
Stream samples are collected at the end of every month at two sites on the East Branch of Wappinger Creek at the Cary Institute of Ecosystem Studies. Before 1996, samples were collected at four sites. Redundancy in the data and cost of analysis prompted us to discontinue collecting samples at two of the sites. The two remaining sites are Site 2 (Fern Glen, GPS coordinates N41.78707, W73.73317) and Site 4 (Lowlands, GPS coordinates N41.79235, W73.74937). Sample collection began in November 1985 (Site 2) and January 1985 (Site 4). Samples are collected when the stream is as near base flow as possible, however, base flow varies seasonally and is generally higher in winter than summer. The samples are analyzed at the Cary Institute Analytical Laboratory for pH, conductivity, nitrate, sulfate, ammonium, phosphate, chloride, sodium, calcium, magnesium, potassium and silica and DOC (see Table 1 for analytical methods).
Samples collected between 1985 and 1998 were not preserved in any way and were stored in the light at room temperature before analyses were completed. Samples from January 1999 onward are preserved as follows. Samples are divided into three aliquots, one aliquot is filtered and preserved with Optima grade concentrated sulfuric acid (0.5 ml per 125 ml of sample) for analysis of nitrate, ammonium, phosphate, and DOC. Another aliquot is filtered and analyzed for sulfate, chloride, sodium, calcium, magnesium, potassium and silica. Silica analyses are completed within 4 days of sample collection. The third aliquot is untreated and analyzed for conductivity and pH.
STREAM CHEMISTRY DATA VARIABLE DESCRIPTIONS WITH UNITS & DETECTION LIMITS
- DATE date sample was collected
- SITE site number on Wappinger Creek
- COND conductivity (umho)
- PH pH
- CA concentration of Ca+2 (mg/L) (DL 0.01 mg/L)
- MG concentration of Mg+2 (mg/L) (DL 0.01 mg/L)
- K concentration of K+ (mg/L) (DL 0.01 mg/L)
- NA concentration of Na+ (mg/L) (DL 0.01 mg/L)
- CL concentration of Cl- (mg/L) (DL 0.02 mg/L)
- SO4 concentration of SO4-2 (mg/L) (DL 0.02 mg/L)
- NO3 concentration of NO3- (mg/L) (DL 0.02 mg/L)
- NH4 concentration of NH4+ (mg/L) (DL 0.02 mg/L)
- PO4 concentration of PO4-3 (mg/L) (DL 0.002 mg/L)
- SIO2 concentration of SiO2 (mg/L) (DL 0.1 mg/L)
- TEMP stream temperature at time of sampling (C)
- DOCPPM concentration of DOC (ppm) (DL 0.05 ppm)
- Q Stream flow rate at time sample collected (m^3/s)
- NO3_N concentration of NO3-_N (mg/L) (DL 0.02 mg/L)
- NH4_N concentration of NH4+_N (mg/L) (DL 0.02 mg/L)
- PO4_P concentration of PO4-3_P (mg/L) (DL 0.002 mg/L)
STREAM CHEMISTRY DATA QUALITY ASSURANCE & QUALITY CONTROL PARAMETERS & METHODS
All sample bottles and glassware were cleaned by rinsing in deionized water 7 times, allowing to soak overnight in deionized water, rinsing again 4 times in deionized water and air dried. Once each year a sample bottle was filled with deionized water, filtered, acidified and analyzed as a regular sample. This was to ensure that the sample handling procedures introduced no contamination.
When analytical results were received from the Cary Institute analytical lab, data were checked by examining time series graphs of sample concentrations for each analyte. Any data that were potential outliers were reanalyzed. If reanalysis returned the same results, no changes were made to the dataset. If reanalysis returned different results, ion balances were examined and the sample was examined for potential contamination. The concentration value that returned the best ion balance was submitted to the dataset unless there was obvious contamination, in which case the data value was replaced with a missing value code.
MISSING VALUE CODES
Missing values are represented either by a single decimal point, an N if the value returned was below detection limit or a Q if there was an insufficient quantity of sample for chemical analysis.
Analytical methods are available upon request.
Stream gauging and temperature equipment is located on the East Branch of Wappinger Creek in the Fern Glen on the Cary Institute property. GPS coordinates for the site are N41.78707, W73.73317. The stream is a tributary to the main branch of Wappinger Creek, which flows into the Hudson River at Wappingers Falls. Approximately 1.6 km upstream from the gauging station is the Village of Millbrook sewage treatment plant. In addition to the sewage treatment plant, Dietrich Pond and its associated dam can influence the stream at the gauging station. The gauging equipment is situated in a stilling well, which is located on the leeward side of an old bridge abutment. Stream height is monitored using a float and pulley system with a graduated tape (formerly a wire). The pulley is connected to an incremental shaft encoder, which is monitored using a datalogger. Stream temperature and conductivity are monitored using a temperature/conductivity sensor, which sits on the bed of the stream near the stilling well. Instantaneous height, temperature and conductivity measurements are recorded and stored every fifteen minutes. Rating curves for estimating stream discharge were developed in 1987-1988, 1993-1994, 1996, 1997-1998 and 2003-2005 with periodic points checked in intervening and subsequent years.
Stream height was measured between 1986 and 1991 using a Leupold and Stevens, Inc. total flow meter (model 61R) connected to a float and pulley. Stream temperature was measured between 1987 and 1993 using a Weksler Instruments Corporation, Temperature Chart Recorder, 10 inch. Data collected prior to 1993 can be made available on request. In 1993, we began continuous collection of stream height and temperature using a Handar, Inc. 570A Data Acquisition System with an incremental shaft encoder (model 436A) and a water temperature sensor (Handar, Inc., model 433FN 1993-Sept. 2003, Campbell Scientific model CS547A May 2005-present). Stream height is checked with a fixed staff gauge (Sept. 1997-present) and with a graduated tape on the pulley (July 2002-present). The Handar 570A datalogger was replaced with a Campbell Scientific CR510 datalogger in September 2003. We began continuous stream conductivity measurements in May 2005 using a Campbell Scientific CS547A conductivity and temperature probe.
Rating Curve Equations:
y = discharge (m^3/s) x = stage height (cm)
1993-1994 y = 0.0009x^2 + 0.0159x + 0.1192 R^2 = 0.9923, n=6
1996 y = 0.0024x^2 - 0.0168x + 0.1444 R^2 = 1, n=3
1997-1998 y = 0.0009x^2 - 0.0036x + 0.0557 R^2 = 0.9934, n=6
2001-2005 y = 0.0018x^2 - 0.0292x + 0.1178 R^2 = 0.9876, n=7
HYDROLOGICAL DATA VARIABLE DESCRIPTIONS WITH UNITS
- DATE Date in MMDDYYYY format where MM is month number, DD is date number and YYYY is year
- HOUR_MIN Hour in hour_minute format in Eastern Standard Time. Note that data are from the preceding 15-minute interval. For example, data for hour 0015 are from midnight to 12:15 am Eastern Standard Time.
- STRM_TMP Stream temperature (degrees Celsius)
- STRM_HT Height of stream (cm)
- STRM_COND conductivity corrected for temp to 25 C (mScm^-1)
- Q stream discharge (m^3/s)
- QUEST_HT Code for if stream frozen, 0 = stream not frozen, 1 = stream frozen, 2 = stream may have been frozen, have no notes.
HYDROLOGICAL INSTRUMENTS- MAKE, MODEL, DATES USED, SENSITIVITY, RECOMMENDED SIGNIFICANT FIGURES
- Stream Height 1986-1991 Leupold and Stevens, Inc. total flow meter (model 61R).
- Stream Height and Temperature April 1993-present Handar, Inc., 570A Data Acquisition System with incremental shaft encoder (model 436A) sensitivity 1/100 of a revolution, (pulley circumference 18 in. April 1993-July 2002, 37.5 cm July 2002-present), recommended significant figures 2; and water temperature sensor (Handar, Inc., model 433FN 1993-Sept. 2003; Campbell Scientific model CS547A May 2005-present) sensitivity 0.2 degrees C, 0.03 mScm^-1 recommended significant figures 2 for temperature, 3 for conductivity. Stream height is checked with a fixed staff gauge Sept. 1997-present and with a graduated tape on the pulley July 2002-present. Handar 570A datalogger was replaced with a Campbell Scientific CR510 datalogger in September 2003. The Handar, model 433FN stream temperature sensor was replaced with a Campbell Scientific CS547A conductivity and temperature probe in May 2005.
- Stream Velocity for rating curves. Marsh-McBirney Model 201M portable water current meter, upgraded to model 2000 in 2002.
HYDROLOGICAL DATA QUALITY ASSURANCE & QUALITY CONTROL PARAMETERS & METHODS
Stream data are downloaded from the datalogger every week. Height data are checked for accuracy by comparing values with the height registered on the pulley tape and on the fixed staff gauge. Weekly checks are made during winter to determine if the stream is frozen at the stilling well. A code value of 0, 1 or 2 is assigned to each line of data to indicate if the stream was frozen. For each weekly dataset a time series graph is used to identify outlier data points. Any erroneous values that are obviously due to equipment malfunction are replaced with missing value codes. Log files are kept with a description of each site visit, and include calibration information, measurement adjustments, probe cleaning, etc.
At the end of each year a time series graph is produced to look for outlier data points. Questionable data are replaced with missing value codes. In November 2001 adjustments were made to stream height data to account for instrument drift and errors in set points. As a result, some of the stream height values are below zero. Details of these adjustments are available upon request.
Instrument notes including calibration schedule, malfunctions and repairs, new instrumentation, anecdotal information etc. can be made available on request.
MISSING VALUE CODES
Missing values are represented by a single decimal point.