The effect of urban land use on stream temperature regimes in the Gwynns Falls and Jennifer Branch (Cub Hill) watersheds
Belt, K., J. Stubbs, and L. Olszewski
We report on stream temperature loggers that were installed at three locations near a flux tower in Cub Hill, Baltimore County. In addition, we compare these measurements to long-term monitoring of stream temperatures at eight of the nine Baltimore Ecosystem Study stream gauging locations. In the Cub Hill area, loggers were placed in a first order stream draining a high density residential area, a first order stream draining a medium density residential area, and in the main stem of Jennifer Branch, a second order stream whose drainage includes the first order streams mentioned above. Data from July and August 2003 indicate that Jennifer Branch, the larger stream, is typically less than 1º C warmer than stream water from the high density watershed and more than 2º C warmer than that from the medium density watershed. Additionally, we see diurnal variation in the temperature differences between the small streams and the larger one. Differences are more pronounced in the late afternoon to early evening, and less pronounced mid-morning. Exceptions occur during storm events when the high density watershed temperatures exceed those of Jennifer Branch and medium density watershed temperatures closely approach them. Storm events are marked in all three locations by abrupt temperature increases breaking from normal diurnal patterns. Long-term stream temperature data in the Gwynns Falls indicate that downstream temperatures (urban) are significantly higher by 2-4 º C than upstream temperatures (forest). Moreover, suburban watersheds were consistently higher by 2-6 º C in temperature than forested watersheds.
stream temperature, cub hill, jennifer branch, urban effects