Mediating stream baseflow response to climate change: The role of basin storage

Abstract

Inter‐basin differences in streamflow response to changes in regional hydroclimatology may reflect variations in storage characteristics that control the retention and release of water inputs. These aspects of storage could mediate a basin's sensitivity to climate change. The hypothesis that temporal trends in stream baseflow exhibit a more muted reaction to changes in precipitation and evapotranspiration for basins with greater storage was tested on the Oak Ridges Moraine (ORM) in Southern Ontario, Canada. Long‐term (>25 years) baseflow trends for 16 basins were compared to corresponding trends in precipitation amount and type and in potential evapotranspiration as well as shorter trends in groundwater levels for monitoring wells on the ORM. Inter‐basin differences in storage properties were characterized using physiographic, hydrogeologic, land use/land cover, and streamflow metrics. The latter included the slope of the basin's flow duration curve and basin dynamic storage. Most basins showed temporal increases in baseflow, consistent with limited evidence of increases and decreases in regional precipitation and snowfall: precipitation ratio, respectively, and recent increases in groundwater recharge along the crest of the ORM. Baseflow trend magnitude was uncorrelated to basin physiographic, hydrogeologic, land use/land cover, or flow duration curve characteristics. However, it was positively related to a basin's dynamic storage, particularly for basins with limited coverage of open water and wetlands. The dynamic storage approach assumes that a basin behaves as a first‐order dynamical system, and extensive open water and wetland areas in a basin may invalidate this assumption. Previous work suggested that smaller dynamic storage was linked to greater damping of temporal variations in water inputs and reduced interannual variability in streamflow regime. Storage and release of water inputs to a basin may assist in mediating baseflow response to temporal changes in regional hydroclimatology and may partly account for inter‐basin differences in that response. Such storage characteristics should be considered when forecasting the impacts of climate change on regional streamflow.

Assessing basin storage: Comparison of hydrometric‐ and tracer‐based indices of dynamic and total storage

“…BFI values were within the range reported for longer streamflow records from 60 basins draining the ORM (Buttle et al, ), and for basins across south central Ontario which included the ORM region (McLean & Watt, ). FDC slopes were similar to values from Buttle () for the 2006–2012 period for several of the basins examined here. Conversely, Burn et al () gave a mean ( Q 5 – Q 95 )/ Q 50 of 7.7 for basins in southern Ontario that exceeds values for most of the study basins (Table ); our lower values likely reflect the role of storage in the ORMAC in mediating translation of inputs to streamflow and producing more stable flow regimes.…”

“…They should also consider the potential scale‐dependence of the influence of such factors as hydrogeologic conditions on the storage indices examined here. Gerber and Howard () and Buttle () noted that lower stream reaches in several basins (e.g. Pefferlaw Br) are incised into deeper aquifers confined by the Newmarket Till.…”

“…The influence of storage on a drainage basin's ability to partition, retain, transfer and release water is well recognized (Wagener, Sivapalan, Troch, & Woods, , McNamara et al, ), and there is increasing acknowledgement that storage may mediate the sensitivity of basin streamflow to land use/land cover (LULC) and climate change (Buttle, ; Clow, Mast, & Sickman, ; Soulsby, Piegat, Seibert, & Tetzlaff, ). Despite its importance in hydrology, estimation of storage at the basin scale is a challenging task, confounded by interactions between attributes influencing the infiltration, retention and release of precipitation inputs to streamflow (Price, ).…”

“…Much focus has been placed on dynamic storage, and approaches for its estimation include recession analysis (e.g. Kirchner, ; Tague & Grant, ), hydrograph separation to determine the baseflow fraction of total runoff (baseflow index, BFI , Smakhtin, ), and the slope of the basin's flow duration curve slope (Buttle, ; Sawicz, Wagener, Sivapalan, Troch, & Carrillo, ). Tracers have been used to estimate the sum of dynamic and passive storage in the basin, sometimes termed “total” storage (Birkel et al, ; Soulsby et al, ).…”

Comparative Analysis of Four Baseflow Separation Methods in the South Atlantic-Gulf Region of the U.S.

“…There was an upward trend with the annual baseflow index in the upstream and no statistically significant difference in middle and downstream in the Loess Plateau in China [24]. Buttle [25] presented that baseflow discharge had an increasing trend and a decreasing trend with total precipitation in Oak Ridges Moraine in Canada. Kahsay et al [26] reported that baseflow decreased in the sub-catchment of the Tekeze basin in Ethiopia from 1994 to 2013.…”