Environmental Hydrology

Abstract

Hyporheic hydrodynamics are a control on stream ecosystems, yet we lack a thorough understanding of catchment controls on these flow paths, including valley constraint and hydraulic gradients in the valley bottom. We performed four whole-stream solute tracer injections under steady state flow conditions at the H. J. Andrews Experimental Forest (Oregon, United States) and collected electrical resistivity (ER) imaging to directly quantify the 2-D spatial extent of hyporheic exchange through seasonal base flow recession. ER images provide spatially distributed information that is unavailable for stream solute transport modeling studies from monitoring wells alone. The lateral and vertical extent of the hyporheic zone was quantified using both ER images and spatial moment analysis. Results oppose the common conceptual model of hyporheic ''compression'' by increased lateral hydraulic gradients toward the stream. We found that the extent of the hyporheic zone increased with decreasing vertical gradients away from the stream, in contrast to expectations from conceptual models. Increasing hyporheic extent was observed with both increasing and decreasing down-valley (i.e., parallel to the valley gradient) and cross-valley (i.e., from the hillslope to the stream, perpendicular to the valley gradient) hydraulic gradients. We conclude that neither cross-valley nor down-valley hydraulic gradients are sufficient predictors of hyporheic exchange flux nor flow path network extent. Increased knowledge of the controls on hyporheic exchange, the temporal dynamics of exchange flow paths, and their the spatial distribution is the first step toward predicting hyporheic exchange at the scale of individual flow paths. Future studies need to more carefully consider interactions between spatiotemporally dynamic hydraulic gradients and subsurface architecture as controls on hyporheic exchange.

Extreme storms and changes in particulate and dissolved organic carbon in runoff: Entering uncharted waters?

“…This event also produced the highest peak discharge (5.0 mm/h) and highest total amount of streamflow discharge (32.7 mm) for the study period. Similarly, the event of 30 September 2010 (event 1) was associated with remnants of hurricane Nicole [ National Oceanic and Atmospheric Administration, NOAA , ] and yielded a rainfall amount of 151 mm and had a precipitation return period of 25 years [Appendix C, Ward and Trimble, ]. Remnants of Hurricane Sandy that lashed the mid‐Atlantic region in October 2012, delivered a total of 139 mm with 119 mm associated with our sampled storm event.…”

“…Total stream discharge measured at the 12‐ha outlet for the 16‐month study period was 497 mm, resulting in an annual runoff ratio of 0.27. The largest amount of precipitation (155 mm) was recorded for the event of 27 August 2011 (event 10, Table ), which was associated with remnants of hurricane Irene [ National Oceanic and Atmospheric Administration, NOAA , ] and had a precipitation return period of 25 years [Appendix C, Ward and Trimble, ]. This event also produced the highest peak discharge (5.0 mm/h) and highest total amount of streamflow discharge (32.7 mm) for the study period.…”

Monitoring and modelling total phosphorus contributions to a freshwater lake with cage-aquaculture

“…The length (L) and width ( b ) of the channel used in equation was 30 m and the depth ( h ) was 4.0 m. The mean cross‐sectional area was 67.7 m 2 . Manning's roughness coefficient ( n ) of 0.02 was applied in equation representing a stone/gravel substrate of the canal (Ward & Trimble ). A Chezy coefficient ( C ) of 55 was chosen after calibration of the model.…”

Transporte de sedimentos na bacia cênica do rio formoso em Bonito/Ms

“…Os sedimentos grosseiros ou de maior granulometria (areia ou classe superior) são transportados sobre o leito através de movimentos de deslizamento ou rolamento (POWELL, 2009;CARVALHO, 2008). O sedimento de fundo é definido como material transportado junto ao leito do rio, por movimentos de deslizamento ou rolagem (GORDON et al, 2004;WARD & TRIMBLE, 2004…”