Data from: Multiple timescales of streambed flux variability in two perennial mountain-front streams

Streambed fluxes are highly variable through time and space, having a
range of implications for stream‐aquifer processes. This study
investigated streambed fluxes over a 3‐year study period to characterize
short‐ and long‐term variations and related implications for seepage
recharge and hyporheic exchange. Time series of streambed fluxes were
estimated through Darcy‐based methods using water level and temperature
inputs from shallow (<1.5 m) nested streambed piezometers installed
in two mountain‐front streams in Colorado, USA. Three predominant temporal
scales of variability were characterized: sub‐daily (<1 day), daily
(>1 day; <1 year), and interannual (>1 year).
Temporal variability was quantified using the median absolute deviation
(MAD), a statistical measure that is resistant to extreme values
associated with short‐duration events. Sub‐daily variability (MADS‐D) was
related to ET, temperature‐induced changes in hydraulic conductivity, and
variable stream stage, and was quantified using the MAD of detrended
fluxes (daily mean subtracted). Daily variability (MADD), calculated as
the MAD of daily median fluxes for a given year, exceeded sub‐daily
variability, and was influenced by strong seasonality at some sites. For
individual sites and water years, the ratio of MADS‐D to MADD ranged from
0.03 to 0.70, with an average of 0.25. Annual median fluxes at each site
varied across years, but typically remained consistent in order of
magnitude and direction. Results reveal a strong linear correlation
between the daily variability and the median annual flux at individual
sites. Within a year, summer months characterized by stronger losing
conditions showed greater overall variability. 1D numerical heat and flow
modelling was performed to calibrate hydraulic parameters and to
investigate temperature‐related controls for sub‐daily variations. We
discuss implications of documented temporal variability for analyses of
hyporheic exchange and groundwater recharge. Results provide a basis for
quantifying temporal variations in streambed fluxes and highlight the
extent to which fluxes vary over multiple timescales.