Using fluorescein and bromide tracers to investigate the role of baseflow in a small suburban watershed in Iowa, USA
S. Rai, University of Northern Iowa
M. Z. Iqbal, University of Northern Iowa
Baseflow, Bromide, Fluorescein, Hydrology, Iowa, Isotope
Hydrological Processes
Fluorescein and bromide tracers were used to study baseflow mechanisms of a small suburban watershed in northeast Iowa, USA. The tracers were applied to ten injection holes ranging from 1.3 to 3.0ft in depth in two phases. Separately, two PVC wells (15 and 16ft deep) were used to investigate tracer movement in a deeper flow system. Over 30days of phase 1, none of the tracers was detected in the creek water. In phase 2, fluorescein was irregularly detected in the creek at two sites, whereas bromide was detected at one site only. Meanwhile, soil analysis detected measurable diffusion of bromide and fluorescein at four sites. At each of these sites, the tracer was found to be diffusing toward the creek. None of the tracers applied to the deeper PVC wells showed any movement toward the creek over 1month of continuous sampling. Isotopic composition of water samples varied spatially as well as temporally going from the deep well (δ18O=-8.89‰) to the injection holes (average δ18O=-8.42‰), to the creek (average δ18O=-7.86‰), and further to the rain samples (average δ18O=-4.68‰). The analytical error margin is ±0.09‰. Samples from the injection holes were generally heavier than the deep well sample and lighter than the creek samples, indicating that there was no significant connection between the surface and the subsurface systems. Furthermore, the sporadic appearance of bromide and fluorescein both spatially and temporally points to the fact that baseflow does not constitute a significant part of the area's stream discharge.
10.1002/hyp.10143
Rai, S. and Iqbal, M. Z., "Using fluorescein and bromide tracers to investigate the role of baseflow in a small suburban watershed in Iowa, USA" (2015). Faculty Publications. 1336.