Reidy, Catherine. 2004. Variability of hyporheic zones in Puget Sound Lowland streams. M.S.

Seven small streams with varying land use in the Puget Sound lowlands of western Washington were evaluated with the following objectives: 1) to estimate the amount of hyporheic exchange and spatial extent of hyporheic zones; 2) to assess hyporheic water quality; and 3) to address seasonal variability of hyporheic exchange among these streams. The study was conducted during 2001-2002, and methods included a combination of numerical modeling of stream tracer data, physical channel and substrate measurements, and analysis of hyporheic water samples collected from piezometers. Results illustrate broad heterogeneity in hyporheic zone exchange rate and spatial extent among the sites examined. Estimates of hyporheic exchange rate coefficient (a) ranged from 0.00004 /s – 0.01277 /s, and estimates of hyporheic zone cross-sectional area (AS) ranged from 0.013 m2– 13.46 m2 . With the exception of the maximum values for both a and AS , results fell within the range of those typically found in published data. An inverse correlation between relative amounts of impervious area within basins and the ability of chloride concentrations (tracer used) and electrical conductivity (surrogate measured) to maintain a linear relationship may have adversely affected modeled results from the stream tracer experiments. Overall, the surface channel and substrate parameters measured or estimated in this study were not tightly correlated to hyporheic exchange rate, spatial extent, or seasonal variation in exchange. Furthermore, fine sediment concentrations in the hyporheic zone did not correlate to hyporheic exchange parameters or dissolved oxygen concentrations as had been expected. Signatures of surface stream temperature dampening by the hyporheic zone varied among and within sites.

Read the full thesis (1.0 MB pdf)

Above pictures: Cathy takes water samples from the middle of Clarks Creek (Pierce County). Graduate student Jeff Shellberg helps Cathy in the field by taking conductivity readings at Colin Creek (King County).