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

Abstract

Storage is a fundamental but elusive component of drainage basin function, influencing synchronization between precipitation input and streamflow output and mediating basin sensitivity to climate and land use/land cover (LULC) change. We compare hydrometric and isotopic approaches to estimate indices of dynamic and total basin storage, respectively, and assess inter-basin differences in these indices across the Oak Ridges Moraine (ORM) region of southern Ontario, Canada. Dynamic storage indices for the 20 study basins included the ratio of baseflow to total streamflow (baseflow index BFI), Q 99 flow and flow duration curve (FDC) slope. Ratios of the standard deviation of the streamflow stable isotope signal relative to that of precipitation were determined for each basin from a 1 year bi-weekly sampling program and used as indicators of total storage. Smaller ratios imply longer water travel times, smaller young water fractions (F yw , <~2-3 months in age) in streamflow and greater basin storage. Ratios were inversely related to BFI and Q 99 , and positively related to FDC slope, suggesting longer travel times and smaller F yw for basins with stable baseflow-dominated streamflow regimes. Inter-basin differences in all indices reflected topographic, hydrogeologic and LULC controls on storage, which was greatest in steep, forest-covered headwaters underlain by permeable deposits with thick and relatively uniform unsaturated zones. Nevertheless, differential sensitivity of indices to controls on storage indicates the value of using several indices to capture more completely how basin characteristics influence storage. Regression relationships between storage indices and basin characteristics provided reasonable predictions of aspects of the streamflow regime of test basins in the ORM region. Such relationships and the underlying knowledge of controls on basin storage in this landscape provide the foundation for initial predictions of relative differences in streamflow response to regional changes in climate and LULC.

Travel times for snowmelt‐dominated headwater catchments: Influences of wetlands and forest harvesting, and linkages to stream water quality

“…The answer likely depends on complex interactions between relative differences in pre‐harvest vegetation transpiration, catchment storage and dominant runoff processes, and how they change following harvest. However, it may be that differences in evapotranspiration and travel time (and thus storage capacity) between these catchments are not enough to result in a substantial difference in post‐harvest response between catchments, in contrast to what might be expected when comparing the shallow soil Turkey Lakes sites to catchments with deep soils and considerably larger storage capacities (Buttle, 2016; Cooke & Buttle, 2020). Clearly, more research is needed on how subsurface hydrologic processes influence catchment response to forest harvesting (McDonnell et al, 2018).…”

Storage in South‐Eastern Australian Catchments

“…In this study, we focus on dynamic and extended dynamic storages as they are readily estimated from available hydrometric data. While we use different methods to derive dynamic and extended dynamic storages, we expect that the estimates obtained from each method should be reasonably comparable to other studies that have used the same definitions of storage (e.g., Buttle, 2016;Cooke & Buttle, 2020;McNamara et al, 2011;Staudinger et al, 2017).…”

Using Stable Water Isotopes to Evaluate the Changing Contribution of Water Age in Three Southern Ontario Agricultural Streams

“…where SD s and SD p correspond to the standard deviation of stream sample and precipitation sample isotopic composition, respectively. While coefficient of variation can be used as the metric of variation (Soulsby et al, 2015a;Bansah & Ali, 2018;Morales & Oswald, 2020), the ratio of the stream standard deviation to the precipitation standard deviation is also used (Tetzlaff et al, 2009;Sánchez-Murillo et al, 2015;Parajulee et al, 2019;Cooke & Buttle, 2020) and was chosen due to the expected similar means between catchments.…”