气候变化领域集成服务门户(CCPortal): The pulse of a montane ecosystem: Coupling between daily cycles in solar flux; snowmelt; transpiration; groundwater; and streamflow at Sagehen Creek and Independence Creek; Sierra Nevada; USA

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DOI	10.5194/hess-24-5095-2020
	The pulse of a montane ecosystem: Coupling between daily cycles in solar flux; snowmelt; transpiration; groundwater; and streamflow at Sagehen Creek and Independence Creek; Sierra Nevada; USA
	Kirchner J.W.; Godsey S.E.; Solomon M.; Osterhuber R.; McConnell J.R.; Penna D.
发表日期	2020
ISSN	1027-5606
起始页码	5095
结束页码	5123
卷号	24 期号:11
英文摘要	Water levels in streams and aquifers often exhibit daily cycles during rainless periods, reflecting daytime extraction of shallow groundwater by evapotranspiration (ET) and, during snowmelt, daytime additions of meltwater. These cycles can aid in understanding the mechanisms that couple solar forcing of ET and snowmelt to changes in streamflow. Here we analyze 3 years of 30 min solar flux, sap flow, stream stage, and groundwater level measurements at Sagehen Creek and Independence Creek, two snow-dominated headwater catchments in California's Sierra Nevada mountains. Despite their sharply contrasting geological settings (most of the Independence basin is glacially scoured granodiorite, whereas Sagehen is underlain by hundreds of meters of volcanic and volcaniclastic deposits that host an extensive groundwater aquifer), both streams respond similarly to snowmelt and ET forcing. During snow-free summer periods, daily cycles in solar flux are tightly correlated with variations in sap flow, and with the rates of water level rise and fall in streams and riparian aquifers. During these periods, stream stages and riparian groundwater levels decline during the day and rebound at night. These cycles are reversed during snowmelt, with stream stages and riparian groundwater levels rising during the day in response to snowmelt inputs and falling at night as the riparian aquifer drains. Streamflow and groundwater maxima and minima (during snowmelt-and ET-dominated periods, respectively) lag the midday peak in solar flux by several hours. A simple conceptual model explains this lag: streamflows depend on riparian aquifer water levels, which integrate snowmelt inputs and ET losses over time, and thus will be phase-shifted relative to the peaks in snowmelt and evapotranspiration rates. Thus, although the lag between solar forcing and water level cycles is often interpreted as a travel-Time lag, our analysis shows that it is mostly a dynamical phase lag, at least in small catchments. Furthermore, although daily cycles in streamflow have often been used to estimate ET fluxes, our simple conceptual model demonstrates that this is infeasible unless the response time of the riparian aquifer can be determined. As the snowmelt season progresses, snowmelt forcing of groundwater and streamflow weakens and evapotranspiration forcing strengthens. The relative dominance of snowmelt vs. ET can be quantified by the diel cycle index, which measures the correlation between the solar flux and the rate of rise or fall in streamflow or groundwater. When the snowpack melts abruptly from snowmelt-dominated cycles to ET-dominated cycles. Melt-out and the corresponding shift in the diel cycle index occur earlier at lower altitudes and on south-facing slopes, and streamflow integrates these transitions over the drainage network. Thus the diel cycle index in streamflow shifts gradually, beginning when the snowpack melts out near the gauging station and ending, months later, when the snowpack melts out at the top of the basin and the entire drainage network becomes dominated by ET cycles. During this long transition, snowmelt signals generated in the upper basin are gradually overprinted by ET signals generated lower down in the basin. The gradual springtime transition in the diel cycle index is mirrored in sequences of Landsat images showing the springtime retreat of the snowpack to higher elevations and the corresponding advance of photosynthetic activity across the basin. Trends in the catchment-Averaged MODIS enhanced vegetation index (EVI2) also correlate closely with the late springtime shift from snowmelt to ET cycles and with the autumn shift back toward snowmelt cycles. Seasonal changes in streamflow cycles therefore reflect catchment-scale shifts in snowpack and vegetation activity that can be seen from Earth orbit. The data and analyses presented here illustrate how streams can act as mirrors of the landscape, integrating physical and ecohydrological signals across their contributing drainage networks. © 2020 Copernicus GmbH. All rights reserved.
语种	英语
scopus关键词	Aquifers; Catchments; Data streams; Drainage; Evapotranspiration; Groundwater resources; Hydrogeology; Orbits; Runoff; Snow; Snow melting systems; Stream flow; Travel time; Vegetation; Water levels; Enhanced vegetation index; Groundwater aquifer; Headwater catchment; Photosynthetic activity; Riparian groundwater; Shallow groundwater; Vegetation activity; Volcaniclastic deposits; Rivers; aquifer; correlation; diel variation; evapotranspiration; Landsat; MODIS; snowmelt; snowpack; transpiration; vegetation index; water level; California; Sierra Nevada [California]; United States
来源期刊	Hydrology and Earth System Sciences
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/159272
作者单位	Kirchner, J.W., Department of Earth and Planetary Science, University of California, Berkeley, CA, United States, Department of Environmental Systems Science, Eth Zurich, Zurich, Switzerland, Swiss Federal Research Institute Wsl, Birmensdorf, Switzerland; Godsey, S.E., Department of Earth and Planetary Science, University of California, Berkeley, CA, United States, Department of Geosciences, Idaho State University, Pocatello, ID, United States; Solomon, M., Department of Geography, University of California, Berkeley, CA, United States; Osterhuber, R., Central Sierra Snow Laboratory, Norden, CA, United States; McConnell, J.R., Division of Hydrological Sciences, Desert Research Institute, Reno, NV, United States; Penna, D., Department of Environmental Systems Science, Eth Zurich, Zurich, Switzerland, Department of Agriculture Food, Environment and Forestry, University of Florence, Florence, Italy
推荐引用方式 GB/T 7714	Kirchner J.W.,Godsey S.E.,Solomon M.,et al. The pulse of a montane ecosystem: Coupling between daily cycles in solar flux; snowmelt; transpiration; groundwater; and streamflow at Sagehen Creek and Independence Creek; Sierra Nevada; USA[J],2020,24(11).
APA	Kirchner J.W.,Godsey S.E.,Solomon M.,Osterhuber R.,McConnell J.R.,&Penna D..(2020).The pulse of a montane ecosystem: Coupling between daily cycles in solar flux; snowmelt; transpiration; groundwater; and streamflow at Sagehen Creek and Independence Creek; Sierra Nevada; USA.Hydrology and Earth System Sciences,24(11).
MLA	Kirchner J.W.,et al."The pulse of a montane ecosystem: Coupling between daily cycles in solar flux; snowmelt; transpiration; groundwater; and streamflow at Sagehen Creek and Independence Creek; Sierra Nevada; USA".Hydrology and Earth System Sciences 24.11(2020).