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.
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This content will become publicly available on March 1, 2024
Impacts of Land Cover Change on the Spatial Distribution of Nonpoint Source Pollution Based on SWAT Model
Nonpoint source (NPS) pollution is a pressing issue worldwide, especially in the Chesapeake Bay, where sediment, nitrogen (N), and phosphorus (P) are the most critical water quality concerns. Despite significant efforts by federal, state, and local governments, the improvement in water quality has been limited. Investigating the spatial distribution of NPS hotspots can help understand NPS pollutant output and guide control measures. We hypothesize that as land cover changes from natural (e.g., forestland) and agricultural to suburban and ultra-urban, the distribution of NPS pollution source areas becomes increasingly spatially uniform. To test this hypothesis, we analyzed three real watersheds with varying land cover (Greensboro watershed for agriculture, Watts Branch watershed for suburban, and Watershed 263 for ultra-urban) and three synthetic watersheds developed based on the Watts Branch watershed, which ranged from forested and agricultural to ultra-urban but had the same soil, slope, and weather conditions. The Soil and Water Assessment Tool (SWAT) was selected as a phenomenological model for the analysis, and SWAT-CUP was used for model calibration and validation. The hydrologic responses of the three real and synthetic watersheds were simulated over ten years (1993–2002 or 2002–2011), and calibration and validation results indicated that SWAT could properly predict the export of runoff and three target NPS pollution constituents (sediment, total nitrogen, and total phosphorus). The results showed that the distribution of NPS pollutant outputs becomes increasingly uniform as land cover changes from agriculture to ultra-urban across watersheds. This research suggests that the spatial distribution of NPS pollution source areas is a function of the major land cover category of study watersheds, and control strategies should be adapted accordingly. If NPS pollution is distributed unevenly across a watershed, hotspot areas output a disproportionate amount of pollution and require more targeted and intensive control measures. Conversely, if the distribution of NPS pollution is more uniform across a watershed, the control strategies need to be more widespread and encompass a larger area.
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- Award ID(s):
- 1824807
- NSF-PAR ID:
- 10448626
- Date Published:
- Journal Name:
- Water
- Volume:
- 15
- Issue:
- 6
- ISSN:
- 2073-4441
- Page Range / eLocation ID:
- 1174
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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