This file describes the data contained within this resources from a series of tracer tests conducted in the H.J. Andrews Experimental Forest in Oregon during the summer of 2010.  Maps showing the two different stream reaches (WS01, WS03) are contained in the main folder. In the work presented here, electrical resistivity transects were set up perpendicular to the stream flow direction and used to image the presence of an electrically conductive tracer in the subsurface, which was used as a proxy for hyporheic exchange extent.  Shallow groundwater wells surrounding the stream reach were used to monitor the hydraulic heads in the wells to establish hydraulic gradients over a range of conditions during baseflow recession. 

There are three folders inside this resource, which are described here:


1) Electrical Resistivity Data – This folder includes electrical resistivity data collected in Watersheds 01 and 03 with an IRIS Syscal Pro. Electrodes were designed and made in-house of PVC pipe and conductive foil material. 

Data are contained in separate files for each Watershed (e.g. Watershed 01) and for each tracer injection (e.g. Injection 1).  The data are not separated by transect, and each transect contains 323 measurements, where rows 1:323 = Transect 1, rows 324:646 = Transect 2, etc. For both watersheds, the first tracer injection test contained only 4 transects.  All other tracer tests contained 6 transects.  

The file ABMN.txt has 4 columns and 323 rows.  Column 1 = A, Column 2 = B, Column 3 = M, Column 4 = N and are the electrode numbers called in for the sequence of resistivity measurements.  A, B are the transmitting pair and M, N are the monitored pair.  

Electrode sites are located approximately 20cm below ground surface for all electrodes.  Exact locations of the electrodes can be found in the attached survey data and are referenced in Cartesian space along with the survey locations for the groundwater monitoring wells in each watershed.  

Each .csv file includes a data file with the following column headings:

Column 1  = 'App_Rho' = Apparent Resistivity   
Column 2 = 'Dev.' = Standard Deviation    
Column 3 = 'Vp' = Voltage at Monitored Electrodes (in mV)    
Column 4 = 'In' = Current on Injected Electrodes (in mA)  
Column 5 = 'Spa.5' = Spacing between Transects (use info from survey file for electrode positioning)  
Column 6 = 'Stack' = Number of times measurement was taken and stacked (averaged)
Column 7 = 'Rs-Check' =  Resistance check (in kOhms)
Column 8 = 'Vab' = Voltage applied to the transmitting electrodes (in V)
Column 9 = 'Tx-Bat'  = Transmission system battery power (in V)
Column 10 = 'Rx-Bat'  = Receiving system battery power (in V) 
Column 11 = 'Temp.' = Temperature inside Syscal Pro (in degrees C) 
Column 12 = 'Date' = Time and Date (MM/DD/YYYY HH:MM:SS)



2) Solute Data – This folder includes data from in-stream and groundwater measurements.  

A small purge pump was used to make conductivity measurements in wells, and were measured with a YSI handheld device (calibration verification conducted weekly). An FMI pump was used with a 42 gallon trashcan to do the controlled tracer injection; salt was general feed salt for livestock from 50lb bags. 

The in-stream conductivity Data were collected with transducers. The files are labeled "WS01_inj1_Loc1_MC.txt", where WS01 = Watershed 01, inj1 = Solute Tracer Injection 1 of 4, Loc1 = Location 1, MC = Middle Channel or DZ = Dead Zone (on edge of channel near shore).



3) Survey and Hydraulic Data – This folder includes a variety of data; see “Attribute_table_VOLTZ” for Metadata description for all data in the “Survey Data and Hydraulic Head Data” Folder. 

Locations for each groundwater observation well and for all electrodes are contained in the folder “Survey Data and Hydraulic Head Data” in filename “Land Survey Data_WS01” and “Land Survey Data_WS03”.  

Locations can be found in Survey Data file "LandSurveyData_WS01.xls" (and _WS03.xls), on the 1st tab "DataForTopo".  

Also included in this folder are hydraulic head measurements collected in an existing well network installed by Steve Wondzell et al., outfitted with Onset Computing’s HOBO water level pressure transducers (U20-001-01) in addition to a few Solinst CTD loggers.  Calibrations were confirmed with a Solinst water level tape periodically during the data collection period.