Variable flushing mechanisms and landscape structure control stream DOC export during snowmelt in a set of nested catchments

Pacific, V. J.; Jencso, K. G.; McGlynn, B. L.

doi:10.1007/s10533-009-9401-1

Cited by 87 publications

(108 citation statements)

References 40 publications

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“…Knowledge of runoff source areas and how they change through time is critical for deciphering water quantity and composition signals measured at the watershed outlet. For example, the transport of DOC to the stream network [e.g., McGlynn and McDonnell, 2003b;Pacific et al, 2010] greatly depends on the spatial extent of contributing areas and the intersection of DOC accumulation and connectivity-driven mobilization of DOC to streams. Temporally dynamic streamflow and composition source areas can change in time, even on individual rain event time scales, and may partially explain observed streamflow solute behavior across a range of systems including but not limited to TCEF.…”

Section: Variable Contributing Areamentioning

confidence: 99%

The spatial and temporal evolution of contributing areas

Nippgen

McGlynn

Emanuel

2015

Water Resources Research

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101

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Predicting runoff source areas and how they change through time is a challenge in hydrology.Topographically induced lateral water redistribution and water removal through evapotranspiration lead to spatially and temporally variable patterns of watershed water storage. These dynamic storage patterns combined with threshold mediation of saturated subsurface throughflow lead to runoff source areas that are dynamic through time. To investigate these processes and their manifestation in watershed runoff, we developed and applied a parsimonious but spatially distributed model (WECOH-Watershed ECOHydrology). Evapotranspiration was measured via an eddy-covariance tower located within the catchment and disaggregated as a function of vegetation structure. This modeling approach reproduced the stream hydrograph well and was internally consistent with observed watershed runoff patterns and behavior. We further examined the spatial patterns of water storage and their evolution through time by building on past research focused on landscape hydrologic connectivity. The percentage of landscape area connected to the stream network ranged from less than 1% during the fall and winter base flow period to 71% during snowmelt. Over the course of the 2 year study period, 90% of the watershed areas were connected to the stream network for at least 1 day, leaving 10% of area that never became connected. Runoff source areas during the event shifted from riparian dominated runoff to areas at greater distances from the stream network when hillslopes became connected. Our modeling approach elucidates and enables quantification and prediction of watershed active areas and those active areas connected to the stream network through time.

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Section: Variable Contributing Areamentioning

confidence: 99%

The spatial and temporal evolution of contributing areas

Nippgen

McGlynn

Emanuel

2015

Water Resources Research

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101

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“…Yet, the difference in the annual hydrological export of DOC between the two catchments was small (<2 %), evidencing the limited capacity of this riparian forest to supply DOC to the stream. Recently, Pacific et al (2010) concluded that riparian systems have an impact on annual stream DOC export only when there is a significant riparian-to-hillslope area ratio (at least 5 %). Concordantly, our results indicated that the FSW riparian forest (2 % of the catchment area) was too small to modify annual stream DOC export in this semiarid catchment.…”

Section: Riparian Vegetation As a Source Of Dissolved Organic Matter mentioning

confidence: 99%

“…There is a large flux of dissolved organic carbon (DOC) from riparian soils to stream ecosystems (e.g. Seibert et al, 2009;Hornberger et al, 1994), and this source of organic matter can contribute considerably to the annual export of DOC at the catchment scale (Inamdar and Mitchell, 2006;Pacific et al, 2010). At the same time, riparian zones can act as important sinks of essential nutrients such as nitrate, substantially reducing nitrate export from catchments (Peterjohn and Correll, 1984;Hill, 1996;Vidon et al, 2004a).…”

Section: Introductionmentioning

confidence: 99%

“…Recent studies performed in temperate regions have revealed that the capability of the alluvial riparian zone to change water and nutrient export from catchments increases with its size (relative to the hillslope area) and with the turnover time of groundwater in this compartment, which is inversely related to the degree of hydrological connectivity between hillslope and riparian zones Pacific et al, 2010). In semiarid catchments, high water demand by vegetation limits water availability and runoff, so that hydrological connectivity between hillslope and riparian zones tends to be low (Piñol et al, 1991;Meixner et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

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Changes in discharge and solute dynamics between hillslope and valley-bottom intermittent streams

Bernal

Sabater

2012

Hydrol. Earth Syst. Sci.

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Abstract. To gain understanding on how alluvial zones modify water and nutrient export from semiarid catchments, we compared monthly discharge as well as stream chloride, carbon, and nitrogen dynamics between a hillslope catchment and a valley-bottom catchment with a well-developed alluvium. Stream water and solute fluxes from the hillslope and valley-bottom catchments showed contrasting patterns between hydrological transitions and wet periods, especially for bio-reactive solutes. During transition periods, stream water export decreased >40 % between the hillslope and the valley bottom coinciding with the prevalence of streamto-aquifer fluxes at the alluvial zone. In contrast, stream water export increased by 20-70 % between the hillslope and valley-bottom catchments during wet periods. During transition periods, stream solute export decreased by 34-97 % between the hillslope and valley-bottom catchments for chloride, nitrate, and dissolved organic carbon. In annual terms, stream nitrate export from the valley-bottom catchment (0.32 ± 0.12 kg N ha −1 yr −1 [average ± standard deviation]) was 30-50 % lower than from the hillslope catchment (0.56 ± 0.32 kg N ha −1 yr −1 ). The annual export of dissolved organic carbon was similar between the two catchments (1.8 ± 1 kg C ha −1 yr −1 ). Our results suggest that hydrological retention in the alluvial zone contributed to reduce stream water and solute export from the valley-bottom catchment during hydrological transition periods when hydrological connectivity between the hillslope and the valley bottom was low.

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“…Given the global relevance of increasing river nutrient concentrations, there is a critical need to develop a thorough mechanistic understanding of the variability and controls on nutrient mobilization and export from river catchments. In particular, identification of the dominant landscape source zones that contribute to nutrient export is often challenging [Bishop et al, 1994;Pacific et al, 2010;Grabs et al, 2012], despite the importance of this for their effective management.…”

Section: Introductionmentioning

confidence: 99%

High‐frequency monitoring of catchment nutrient exports reveals highly variable storm event responses and dynamic source zone activation

et al. 2017

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Storm events can drive highly variable behavior in catchment nutrient and water fluxes, yet short‐term event dynamics are frequently missed by low‐resolution sampling regimes. In addition, nutrient source zone contributions can vary significantly within and between storm events. Our inability to identify and characterize time‐dynamic source zone contributions severely hampers the adequate design of land use management practices in order to control nutrient exports from agricultural landscapes. Here we utilize an 8 month high‐frequency (hourly) time series of streamflow, nitrate (NO3‐N), dissolved organic carbon (DOC), and hydroclimatic variables for a headwater agricultural catchment. We identified 29 distinct storm events across the monitoring period. These events represented 31% of the time series and contributed disproportionately to nutrient loads (42% of NO3‐N and 43% of DOC) relative to their duration. Regression analysis identified a small subset of hydroclimatological variables (notably precipitation intensity and antecedent conditions) as key drivers of nutrient dynamics during storm events. Hysteresis analysis of nutrient concentration‐discharge relationships highlighted the dynamic activation of discrete NO3‐N and DOC source zones, which varied on an event‐specific basis. Our results highlight the benefits of high‐frequency in situ monitoring for characterizing short‐term nutrient fluxes and unraveling connections between hydroclimatological variability and river nutrient export and source zone activation under extreme flow conditions. These new process‐based insights, which we summarize in a conceptual model, are fundamental to underpinning targeted management measures to reduce nutrient loading of surface waters.

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Variable flushing mechanisms and landscape structure control stream DOC export during snowmelt in a set of nested catchments

Cited by 87 publications

References 40 publications

The spatial and temporal evolution of contributing areas

The spatial and temporal evolution of contributing areas

Changes in discharge and solute dynamics between hillslope and valley-bottom intermittent streams

High‐frequency monitoring of catchment nutrient exports reveals highly variable storm event responses and dynamic source zone activation

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