Isotope hydrograph separations and rapid delivery of pre-event water from drainage basins

Abstract

Environmental isotopes, such as oxygen-18 and deuterium, have been used increasingly to separate stormflow into its event and pre-event components in order to elucidate the sources, pathways and residence times of water in drainage basins. The majority of isotopic hydrograph separations indicate that pre-event water supplies at least 50% of streamflow at peak discharge in small- and medium-sized basins; however, there is no consensus as to the means by which pre-event water is rapidly exported from drainage basins. The hydrological processes that have been invoked to explain the observed isotopic response of streamflow to rainfall and snowmelt inputs in various environments are reviewed. These processes include groundwater ridging, translatory flow, macropore flow, saturation overland flow, kinematic waves and release of water from surface storage. Tests of the ability of the hypothesized mechanisms to explain the isotopic signature of stormflow from drainage basins will require a more complete integration of hydrometric methods with the use of environmental isotopes than has been achieved previously. Along with various methodological issues associated with the isotopic hydrograph separation technique, the overall relevance of these hydrograph separations to the understanding and prediction of stream hydrochemistry must be evaluated critically.

Identification of runoff generation processes using hydrometric and tracer methods in a meso-scale catchment in Rwanda

“…Sklash and Farvolden (1979), Wels et al (1991), Buttle (1994) and Uhlenbrook and Hoeg (2003). The mass balance expression for a two-component hydrograph separation model used in this paper is described as follows:…”

Categorisation of northern California rainfall for periods with and without a radar brightband using stable isotopes and a novel automated precipitation collector

“…Typically, environmental stable hydrogen and oxygen-isotope measurements are used in catchment hydrology studies to (1) determine the mechanisms and processes involved in the generation and discharge of streamflow, (2) estimate residence-time distributions of water within the catchment, (3) determine the origin of streamflow components, (4) calibrate or validate catchment streamflow models, (5) predict catchment response and (6) estimate hydrologic parameters (Turner and Barnes, 1998). Hydrograph separation is based on the following five assumptions (Sklash et al, 1976;Sklash and Farvolden, 1979;Moore, 1989;Buttle, 1994;Klaus and McDonnell, 2013): (1) The isotopic content of the event and the pre-event water are significantly different. (2) The event water maintains a constant isotopic signature in space and time, or any variations can be accounted for.…”

Characteristics of water isotopes and hydrograph separation during the wet season in the Heishui River, China

“…Stable isotopes D and 18 O have been successfully used to identify water sources (Sklash, 1990;Buttle, 1994) and separated hydrograph for computing the contributions of numerous water sources in a small spatial scale (e.g. Sklash, 1990;McDonnell et al, 1990;Kendall and McDonnell, 1998).…”