This file consists of depth data collected using a HOBO datalogger deployed in a stilling well in the stream channel.

HOBO Datalogger:  Depth and water temperature are recorded by the HOBO data logger.  Depths are corrected for barometric pressure changes using readings in an additional HOBO datalogger deployed at Marshview Farm.  The HOBO is deployed in a PVC tube, which was attached to ree-bar driven into the stream bed.  The PVC tube has holes drilled to allow adequate water circulation. 

ADDITIONAL RESEARCH LOCATION COORDINATES:  In addition to the decimal degree coordinates given above, locations are also given here in Massachusetts State Plane coordinates.  The stream is called SawMill Br. and is located in Burlington MA.  Small amounts of forest remain (~14% in 1999), much of which is along the stream channel near the gaging site.

STATION       STATE X           STATE Y
YSI-SB            225840             919310

NOTES AND COMMENTS:
A fallen tree upstream of the monitoring station in 2016 affected the geomorphology and sediment deposition within in the stream. As a result, the monitoring station began accumulating sediment in the Fall of 2016,and by Spring 2017 was noitceably affecting stage readings. The monitoring station was thus moved to the opposite side of the stream on May 20, 2017 at approximately 9:30 AM EST, but reamined within the same hydrological control. Staff gage readings and discharge measurements taken since the move confirm a stage offset of 0.10m. That is, 0.10 m is subtracted from all depth readings from May 20, 2017 at 9:30 AM EST and later. With this correction, the current rating curve remains in place (see below) with an r2 value of 0.98.

CALCULATIONS:
Discharge rating curve :
Discharge (l/s) = 1380.4*depth^4.4564
where depth is Adj_HOBO_Depth

CORRECTION FACTOR:
Since our Hobo dataloggers are placed in stream reaches with minimal artificial engineering (i.e. v-notch weirs, etc.), there are occasional environmental factors than influence the Hobo depth readings that must be corrected to accurately reflect the true conditions of the stream reach.  These include silt/sand build-up in and around the stilling well or downstream debris dams that artificially elevate the water level of the pool where the hobo is located.  We attempt to correct these changes to provide best estimates of stream depth and corresponding discharge.  Especially with debris dams, we assume a slow build-up of debris and apply an accumulating off-set based on the amount of time betwen site visits.  We note the reasons for all corrections using the "Flag" column in the spreadsheet and the explanations are below.

Flag - NA not available