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: There appears to have been a major shift in the rating curve in early 2010. Discharge estimated in January 2010 is calculated using the old rating curve. For the old rating curve, velocity measurements were made using a Marsh McBirney current meter and contains measurements up to a stage depth of 1.2 meters, which is above bankfull stage. Rating curve has an R2 of 0.88 using 40 measurements between 2001 and 2009. Prior to 2007, stage was measured with various other instruments (YSI, Sigma depth sonde, HOBO). All files in this series (2001-2009) are now standardized to HOBO depth. The rating curve is based on the standardized HOBO depth's (and actual HOBO depths since 2007). CALCULATIONS: Discharge rating curve : Discharge (l/s) = 896.47*depth^5.7352 where depth is Adj_HOBO_Depth For all discharge estimates after March 2010, a new rating curve was used. Starting in 2010, discharge measurements are being made with a Sontek FlowTracker. The new rating curve has an R2 of 0.96 and includes 13 discharge measurements at flows below bankful taken after March 2010 and 2 measurements that were taken at flows above bankful in 2006. CALCULATIONS: Discharge rating curve : Discharge (l/s) = 1380.4*depth^4.4564 where depth is Adj_HOBO_Depth MISSING DATA: Data is missing between 2010-1-30 and 2010-3-9 and between 2010-8-26 and 2010-9-1. 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. Flags: 1 -- Discharge estimated using old rating curve 2 -- Accumulating offset to adjust for change to hobo stilling well (0.116 m) that occurred on June 18 3 -- Accumulating offset to adjust for slow build-up of debris dam (0.02 m) in riffle downstream that elevated pool height