Baltimore Ecosystem Study stream chemistry for upper tributaries of Gwynns Falls watershed: concentration of Cl, NO3, PO4, total N and P, SO4, dissolved oxygen, E. coli, plus temperature, pH, clarity and turbidity

In the Baltimore urban long-term ecological research (LTER) project, (Baltimore Ecosystem Study, BES) we use the watershed approach to evaluate integrated ecosystem function. The LTER research is centered on the Gwynns Falls watershed, a 17,150 ha catchment that traverses a gradient from the urban core of Baltimore, through older urban residential (1900 - 1950) and suburban (1950- 1980) zones, rapidly suburbanizing areas and a rural/suburban fringe. Our long-term sampling network includes four longitudinal sampling sites along the Gwynns Falls as well as several small (40 - 100 ha) watersheds located within or near to the Gwynns Falls. The longitudinal sites provide data on water and nutrient fluxes in the different land use zones of the watershed (rural/suburban, rapidly suburbanizing, old suburban, urban core) and the small watersheds provide more focused data on specific land use areas (forest, agriculture, rural/suburban, urban). Each of the gaging sites is continuously monitored for discharge and is sampled weekly for chemistry. Additional chemical sampling is carried out in a supplemental set of sites to provide a greater range of land use. Weekly analyses includes nitrate, phosphate, total nitrogen, total phosphorus, chloride and sulfate, total suspended solids, turbidity, fecal coliforms, temperature, dissolved oxygen and pH. Cations, dissolved organic carbon and nitrogen and metals are measured on selected samples. This dataset presents stream chemistry from the Upper Gwynns Falls tributaries. From April 1999 to August 2000 Johns Hopkins University graduate student Mark Colosimo sampled a group of sites in the Upper Gwynns Falls (Red Run, Horsehead Branch, Scotts Level Branch, Holly Branch). There were two sites in the Red Run drainage. This watershed drains approximately 19 km2 and has been rapidly suburbanizing since the early 1990s. Percent impervious surface was approximately 10% as of 2002. Sampling station Red Run 1 (RR1) was approximately 35 m upstream of the crossing of Painters Mill Bridge Road, and 350 m upstream of the confluence with the Gwynns Falls. Sampling station Red Run 2 (RR2) was farther upstream, between the Pleasant Hill and Dolfield road crossings. There were two sites along Scotts Level Branch, an older suburban watershed which was approximately 25% impervious surface in 1970. Site SL1 drains approximately 11 km2 and is located at the outlet of the sub-watershed, just above the confluence with Gwynns Falls. Site SL2 is at the McDonogh Rd. bridge crossing. The Horsehead Branch (HH) sampling site was located at the McDonogh Road crossing. It drains approximately 5 km2 that has undergone rapid urbanization since the mid 1980s. As of 1997 percent impervious surface was approximately 12%. The Holly Bank (HB) sampling site was located just upstream of Gwynnbrook Ave. Seventy percent of land in this drainage is classified residential. The Gwynns Falls at McDonogh (GF5) site was located at the McDonogh school / McDonogh road crossing of the Gwynns Falls and samples a drainage area of approximately 51 km2, with approximately 20% impervious surface. Codes and abbreviations: Code,Site name,Watershed type RR1,Red Run at Painters Mill Bridge Road,Suburban RR2,Red Run between Pleasant Hill and Dolfield Roads,Suburban SL1,Scotts Level Branch at Gwynns Falls,Suburban SL2,Scotts Level Branch at McDonogh Road,Suburban HH,Horsehead Branch at McDonogh Road,Suburban HB,Holly Branch at Gwynnbrook Avenue,Suburban GF5,Gwynns Falls at McDonogh Road,Suburban Units and Columns: Column,Variable (units) A,Date B,Year C,Julian Date D,Site E,Cl (mg/L) F,NO3 (mg N/L) G,PO4 (ug P/L) H,SO4 (mg/L) I,TN (mg N/L) J,TP (ugP/L) K,time L,stage (ft) M,temperature (deg C) N,dox (mg/L) O,ph P,clarity Q,Turbidity (NTU) R,Ecoli (CFU/100 mL) Methods: Samples were collected weekly at an established sampling location at each station. Sampling locations were chosen based on adequate concentration of flow, proximity to weir and staff gage, and low vulnerability to disturbance. Samples were collected and stored in polyethylene bottles. Weekly analyses included nitrate, phosphate, total nitrogen, total phosphorus, chloride and sulfate. Samples for anion and cation analysis were filtered (0.45 micron). Every six weeks, samples were shipped to the Cary Institute of Ecosystem Studies (CIES) for anion, cation, TN, and TP analysis. One blank from the laboratory distilled water source was prepared each week and stored along with the samples. Spike analysis was done as part of the routine long-term BES stream sampling and analysis. Samples were stored at 4 degrees C. Concentrations of nitrate, chloride and sulfate were analyzed on a Dionex LC20 series ion chromatograph. Concentrations of phosphate were analyzed on a Lachat Quikchem 8000 flow injection analyzer. Total nitrogen and phosphorus were analyzed by persulfate digestion followed by analysis of nitrate and phosphate on a Lachat Quikchem 8000 flow injection analyzer. If the value for total N was more than 0.10 mg N L-1 less than nitrate-N, the total N value for that sample was set to the nitrate value. If the value for total P was more than 0.01 mg P L-1 less than the phosphate P, the total P value for that sample was set to the phosphate value.