Fig 1.
Simple graphical representation of transient storage zone hydrology within a hyporheic zone.
Grey boxes represent transient storage zones (TSZs) with associated hyporheic water storage (s) with water age between τi−1 and τi. White arrows represent water recharging the aquifer (), flow between TSZs (
) or water discharging from the aquifer (
).
Fig 2.
Visualization of the non-contiguous nature of TSZs within floodplain aquifers.
Isochronal surfaces (“ribbons” in lower panel) demarcate TSZ’s within floodplain alluvial aquifers. Upper panel shows an aerial photo of the floodplain surface. Visualization was created using simulation results derived from an application of the HydroGeoSphere model [35] to the Meacham Creek (Oregon, USA) floodplain restoration conducted by the Confederated Tribes of the Umatilla Indian Reservation (Byron Amerson, Unpublished). Aerial imagery from the National Agriculture Imagery Program [36].
Fig 3.
Graphical representation of a probability density function proportional to a power-law.
The area (shaded) is used to determine a probability density function (PDF) defined by τ0 to τn, assuming the PDF is proportional to a power law.
Table 1.
Some reported values of α based on experimental tracer releases.
Fig 4.
Cumulative hyporheic discharge to the channel (log scale) by water age (log scale) for a representative unit (RU) of water stored in a hyporheic zone.
Each curve is associated with a different value of α, the negative power-law exponent used to describe the hyporheic water age distribution of hyporheic discharge. Units of hyporheic exchange (y-axis) can be interpreted in terms of length (e.g., m day−1), area (e.g., m2 day−1), or volume (e.g., m3 day−1) depending on whether the RU is one dimensional (e.g., 1 m of hyporheic water thickness), two dimensional (e.g., 1 m2 of hyporheic water cross-sectional area), or three dimensional (e.g., 1 m3 of hyporheic water). Hash marks on each curve demarcate the maximum water age (τi) for each of 50 transient storage zones (TSZs) in the RU; each TSZ contains 2% (0.02 mx) of water stored in the RU.
Fig 5.
Quantitative depiction of hyporheic hydraulic geometry for different values of α.
Pie chart represents 50 transient storage zones (TSZs) within a representative unit (RU; 1 mx) of hyporheic water stored within the hyporheic zone. Each TSZ contains 2% (0.02 mx) of the RU’s water storage; color represents the mean water age of each TSZ. The area of superimposed grey wedges is proportional to the water units discharged to the channel from each TSZ in a 1 h period. The 1 h time-scale of depicted discharge can be inferred from plot because, at τ = 1 h, the storage and discharge wedges are equal in area. The nautilus shaped distribution of grey wedges describes the relative water discharge from each TSZ, while the color distribution represents water age across TSZs within the hyporheic zone.
Fig 6.
Visualization of hyporheic water exchange in an annular flume.
(a) Cut-away diagram of the annular flume. (b) Observed (points) and modeled (line) surface water specific conductance. Modeled data derived by fitting values of τn and α to observed data using Eqs 15 and 16. (c) Visualized relationship among water age, hyporheic exchange, and interstitial water storage in the flume. Grey wedges represent aquifer discharge rates for a period of 10 seconds.
Fig 7.
Characteristic temperature damping and lagging with water age in an expansive hyporehic zone based on relationships presented by Helton et al. [47].
Lines represent idealized patterns of temperature along a “representative flow path” through an expansive coarse-grained alluvial aquifer for four different dates (approximate annual maximum, minimum, and mean stream temperatures) as a function of water age. Each line on the daily temperature plot (left) represents the expected pattern of temperature variation for a different hour of the day. Daily temperature variation damps quickly with water age. Seasonal variation in temperature (right) is visible at greater water ages.
Fig 8.
Simulated patterns of mean water temperature within the channel, the alluvial aquifer and upwelling from the aquifer.
Simulated patterns of mean temperature for water discharged from the alluvial aquifer (light grey) and stored within an idealized alluvial aquifer (black) plotted with channel water temperature (dark grey; dashed) over time for different values of α.