Short‐ and long‐term evapotranspiration rates at ecological restoration sites along a large river receiving rare flow events          下载免费PDF全文

Margaret Shanafield  Hugo Gutiérrez‐Jurado  Jesús Eliana Rodríguez‐Burgueño  Jorge Ramírez‐Hernández  Christopher J. Jarchow  Pamela L. Nagler 《水文研究》2017,31(24):4328-4337

Many large rivers around the world no longer flow to their deltas, due to ever greater water withdrawals and diversions for human needs. However, the importance of riparian ecosystems is drawing increasing recognition, leading to the allocation of environmental flows to restore river processes. Accurate estimates of riparian plant evapotranspiration (ET) are needed to understand how the riverine system responds to these rare events and achieve the goals of environmental flows. In 2014, historic environmental flows were released into the Lower Colorado River at Morelos Dam (Mexico); this once perennial but now dry reach is the final stretch to the mighty Colorado River Delta. One of the primary goals was to supply native vegetation restoration sites along the reach with water to help seedlings establish and boost groundwater levels to foster the planted saplings. Patterns in ET before, during, and after the flows are useful for evaluating whether this goal was met and understanding the role that ET plays in this now ephemeral river system. Here, diurnal fluctuations in groundwater levels and Moderate Resolution Imaging Spectroradiometer (MODIS) data were used to compare estimates of ET specifically at 3 native vegetation restoration sites during 2014 planned flow events, and MODIS data were used to evaluate long‐term (2002–2016) ET responses to restoration efforts at these sites. Overall, ET was generally 0–10 mm d^?1 across sites, and although daily ET values from groundwater data were highly variable, weekly averaged estimates were highly correlated with MODIS‐derived estimates at most sites. The influence of the 2014 flow events was not immediately apparent in the results, although the process of clearing vegetation and planting native vegetation at the restoration sites was clearly visible in the results.  相似文献   

OSL signal resetting in young deposits determined with a pulsed photon‐stimulated luminescence (PPSL) unit     

Esperanza Muñoz‐Salinas  Miguel Castillo  José Luis Arce 《Boreas: An International Journal of Quaternary Research》2017,46(2):325-337

Optical Stimulated Luminescence (OSL) is a technique that can be used for dating geological materials deposited within the last half‐million years, including sediments transported by air, water or gravity, as well as rocks heated at high temperatures. Recently, several studies have shown that OSL can also provide information on sediment transport. The pulsed photon‐stimulated luminescence (PPSL) unit (also known as a portable OSL reader) developed by the Scottish Universities Environmental Research Centre is an instrument designed to read luminescence signals from bulk (untreated) sediment samples comprising poly‐mineral and poly‐grain fractions. In this contribution, we evaluate the potential of the PPSL unit to assess the degree of OSL signal resetting in 27 young deposits (<2 ka) transported by different geomorphic agents in volcanic, coastal and fluvial depositional settings located in Mexico. Our results are in agreement with previous findings that used the Risø TL/OSL reader, confirming that sediments transported by debrisflows contain the highest inherited luminesce signals. Infrared stimulation (IRSL) values in volcanic ash, lavas, and sand beach and dune deposits exhibit low scatter. However, with blue stimulation (BLSL) these samples reveal a large degree of scattering, attributed to charge transfer in the case of the coastal deposits and to the low sensitivity of quartz in the case of volcanic material. The luminescence signals of fluvial sediments exhibit a highly scattered distribution in both IRSL and BLSL. We conclude that the use of a PPSL unit is a simple approach to assess the degree of OSL signal resetting in deposits sourced from different geological environments. This research contributes to previous studies that have investigated new applications of the PPSL unit to assist in OSL dating of geological materials.  相似文献   

Stormflow concentration–discharge dynamics of suspended sediment and dissolved phosphorus in an agricultural watershed     

Lucy A. Rose  Diana L. Karwan 《水文研究》2021,35(12):e14455

Concentration–discharge (C-Q) relationships are an effective tool for identifying watershed biogeochemical source and transport dynamics over short and long timescales. We examined stormflow C-Q, hysteresis, and flushing patterns of total suspended sediment (TSS) and soluble reactive phosphorus (SRP) in two stream reaches of a severely impaired agricultural watershed in northeastern Wisconsin, USA. The upper watershed reach—draining a relatively flat, row crop-dominated contributing area—showed predominantly anti-clockwise TSS hysteresis during storms, suggesting that particulate materials were mobilized more from distal upland sources than near- and in-channel areas. In contrast, the incised lower watershed reach produced strong TSS flushing responses on the rising limb of storm hydrographs and clockwise hysteresis, signalling rapid mobilization of near- and in-channel materials with increasing event flows. C-Q relationships for SRP showed complex patterns in both the upper and lower reaches, demonstrating largely non-linear chemodynamic C-Q behaviour during events. As with TSS, anti-clockwise SRP hysteresis in the upper reach suggested a delay in the hydrologic connectivity between SRP sources and the stream, with highly variable SRP concentrations during some events. A broad range of clockwise, anti-clockwise, and complex SRP hysteresis patterns occurred in the lower watershed, possibly influenced by in-channel legacy P stores and connection to tile drainage networks in the lower watershed area. Total suspended sediment and SRP responses were also strongly related to precipitation event characteristics including antecedent precipitation, recovery period, and precipitation intensity, highlighting the complexity of stormflow sediment and phosphorus responses in this severely impaired agricultural stream.  相似文献   

Analysis of extreme rainfall in the Ebre Observatory (Spain)     

Núria Pérez-Zanón  M. Carmen Casas-Castillo  Raúl Rodríguez-Solà  Juan Carlos Peña  Anna Rius  J. Germán Solé  Ángel Redaño 《Theoretical and Applied Climatology》2016,124(3-4):935-944

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Partial duration series distributions of the European dry spell lengths for the second half of the twentieth century     

C. Serra  Xavier Lana  A. Burgueño  M. D. Martínez 《Theoretical and Applied Climatology》2016,123(1-2):63-81

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Changes in surface solar radiation in Northeastern Spain over the past six centuries recorded by tree-ring δ13C     

I. Dorado-Liñán  A. Sanchez-Lorenzo  E. Gutiérrez Merino  O. Planells  I. Heinrich  G. Helle  E. Zorita 《Climate Dynamics》2016,47(3-4):937-950

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Abrupt transitions in the NAO control of explosive North Atlantic cyclone development     

Iñigo Gómara  Belén Rodríguez-Fonseca  Pablo Zurita-Gotor  Sven Ulbrich  Joaquim G. Pinto 《Climate Dynamics》2016,47(9-10):3091-3111

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Urban seismic risk index for Medellín,Colombia, based on probabilistic loss and casualties estimations     

Mario A. Salgado-Gálvez  Daniela Zuloaga Romero  César A. Velásquez  Martha L. Carreño  Omar-Darío Cardona  Alex H. Barbat 《Natural Hazards》2016,80(3):1995-2021

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Influence of Mussel Culture on the Vertical Export of Phytoplankton Carbon in a Coastal Upwelling Embayment (Ría de Vigo,NW Iberia)     

M. Froján  F. G. Figueiras  D. Zúñiga  F. Alonso-Pérez  B. Arbones  C. G. Castro 《Estuaries and Coasts》2016,39(5):1449-1462

The goal of this paper is to find out whether suspended mussel culture affects the vertical fluxes of biogenic particles in the Ría de Vigo on a seasonal scale. With this aim, vertical fluxes of particulate organic carbon (POC) and the magnitude and composition of vertical export of phytoplankton carbon (Cphyto) collected in sediment traps were examined by comparing data obtained inside a mussel farming area (RaS) with those found at a reference station (ReS) not affected by mussels. Our results indicate that mussel farming has a strong impact on sedimentation fluxes under the rafts, not only increasing POC flux but also altering the magnitude and composition of Cphyto fluxes. Average POC flux at RaS (2564?±?1936 mg m^?2 day^?1) was four times higher than at ReS (731?±?276 mg m^?2 day^?1), and much of this increase was due to biodeposit fluxes (Cbiodep) which accounted for large proportion of POC flux (35–60 %). Indeed, because of this high Cbiodep flux, only a small proportion of the POC flux was due to Cphyto flux (3–12 %). At the same time, we observed an increased sedimentation of phytoplankton cells at RaS that could be explained by a combination of mechanisms: less energetic hydrodynamic conditions under mussel rafts, ballast effect by sinking mussel feces, and diatom aggregates. Moreover, mussel farming also altered the quality of the Cphyto flux by removing part of the predatory pressure of zooplankton and thus matching diatom composition in water column and sediment traps.  相似文献   

A robust debris-flow and GLOF risk management strategy for a data-scarce catchment in Santa Teresa,Peru     

Holger Frey  Christian Huggel  Yves Bühler  Daniel Buis  Maria Dulce Burga  Walter Choquevilca  Felipe Fernandez  Javier García Hernández  Claudia Giráldez  Edwin Loarte  Paul Masias  Cesar Portocarrero  Luis Vicuña  Marco Walser 《Landslides》2016,13(6):1493-1507

The town of Santa Teresa (Cusco Region, Peru) has been affected by several large debris-flow events in the recent past, which destroyed parts of the town and resulted in a resettlement of the municipality. Here, we present a risk analysis and a risk management strategy for debris-flows and glacier lake outbursts in the Sacsara catchment. Data scarcity and limited understanding of both physical and social processes impede a full quantitative risk assessment. Therefore, a bottom-up approach is chosen in order to establish an integrated risk management strategy that is robust against uncertainties in the risk analysis. With the Rapid Mass Movement Simulation (RAMMS) model, a reconstruction of a major event from 1998 in the Sacsara catchment is calculated, including a sensitivity analysis for various model parameters. Based on the simulation results, potential future debris-flows scenarios of different magnitudes, including outbursts of two glacier lakes, are modeled for assessing the hazard. For the local communities in the catchment, the hazard assessment is complemented by the analysis of high-resolution satellite imagery and fieldwork. Physical, social, economic, and institutional vulnerability are considered for the vulnerability assessment, and risk is eventually evaluated by crossing the local hazard maps with the vulnerability. Based on this risk analysis, a risk management strategy is developed, consisting of three complementing elements: (i) standardized risk sheets for the communities; (ii) activities with the local population and authorities to increase social and institutional preparedness; and (iii) a simple Early Warning System. By combining scientific, technical, and social aspects, this work is an example of a framework for an integrated risk management strategy in a data scarce, remote mountain catchment in a developing country.  相似文献