The ecohydrological imprint of deforestation in the semiarid Chaco: insights from the last forest remnants of a highly cultivated landscape          下载免费PDF全文

Raúl Giménez  Jorge Mercau  Marcelo Nosetto  Ricardo Páez  Esteban Jobbágy 《水文研究》2016,30(15):2603-2616

The semiarid Chaco plains present one of the highest rates of forest clearing and agricultural expansion of the world. In other semiarid plains, such massive vegetation replacements initiated a groundwater recharge and salt mobilization process that, after decades, raised regional water tables and salts to the surface, degrading agricultural and natural ecosystems. Indirect evidence suggests that this process (known as dryland salinity) began in the Chaco plains. Multiple approaches (deep soil profiles, geoelectric surveys and monitoring of groundwater salinity, level and isotopic composition) were combined to assess the dryland salinity status in one of the oldest and most active agricultural hotspots of the region, where isolated forest remnants occupy an extremely flat cultivated matrix. Full vadose moisture and chloride profiles from paired agriculture‐forest stands (17 profiles, six sites) revealed the following: a generalized onset of deep drainage with cultivation (32 to >87 mm year^?1), full leaching of native chloride pools (13.7 ± 2.5 kg m^?2) down to the water table after >40 years following clearing and differential groundwater table rises (0.7 to 2 m shallower water tables under agriculture than under neighbouring forests). Continuous level monitoring showed abrupt water table rises under annual crops (up to 2.6 m in 15 days) not seen under forests or pastures. Varying deep drainage rates and groundwater isotopic composition under agricultural plots suggest that these pulses are strongly modulated by crop choices and sequences. In contrast to other dryland salinity‐affected areas of the world, forest remnants in the study area (10–20% of the area) are not only surviving the observed hydrological shifts but also sustaining active salty groundwater transpirative discharge, as evidenced by continuous water table records. The overall impact of these forest remnants on lowering neighbouring water tables would be limited by the low hydraulic conductivity of the sediments. As highly cultivated areas of the Chaco evolve to new hydrological conditions of shallower saline water tables, innovative crop rotations that minimize recharge, enhance transpirative discharge and tolerate salinity will be needed. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Surface water quality in a sulfide mineral‐rich arid zone in North‐Central Chile: Learning from a complex past,addressing an uncertain future          下载免费PDF全文

Mauricio Flores  Jorge Núñez  Jorge Oyarzún  Gustavo Freixas  Hugo Maturana  Ricardo Oyarzún 《水文研究》2017,31(3):498-513

This study presents an analysis of up to 30 years of hydrological variables and selected water quality parameters (pH, SO₄, Fe, Cu, and As) in the upper area of the Elqui River basin in North‐Central Chile. A correlation analysis determined statistically significant positive relationship for SO₄‐Cu, Fe‐As, and Fe‐Cu. In terms of historical behaviour, no statistically significant trends were detected for precipitation or temperature. In contrast, for flow, there is an overall decreasing pattern for the entire area of study, although only in one case this trend was statistically significant. Along with the aforementioned analysis, a characterization of the flow‐water quality relationships is considered for the time period analyzed. Although erratic behaviours were confirmed, a negative (i.e., inverse) flow‐concentration relationship was identified for SO₄, a positive (i.e., direct) relationship for Fe, and undefined relationships for As and Cu were obtained. From these analyses and based on previous studies on projections regarding climate change for the Andean region, and in particular for the upper Elqui zone, an estimation of the possible effects of the change in water regimes on water quality in the area of study is developed. It is likely that a decrease in surface flow, as a consequence of climate change could translate into improvements in water quality in terms of Fe and eventually As and Cu, but into an impairment in the case of SO₄. In any case, this is a complex situation that demands special attention in the face of industrial activities that could be developed in tributaries like the Claro River, which currently play an important role in depurating or diluting contaminants in the waters of the Elqui River. Finally, it should be noted that this study addresses an issue that goes beyond the local interest and could be used as a reference to compare other transitional environments containing sulphide ores or areas of hydrothermal alterations, which are considered to be highly vulnerable to climate change and variability.  相似文献   

Modelling non-stationary water ages in a tropical rainforest: A preliminary spatially distributed assessment     

Alicia Correa  Christian Birkel  Jason Gutierrez  Joni Dehaspe  Ana María Durán-Quesada  Chris Soulsby  Ricardo Sánchez-Murillo 《水文研究》2020,34(25):4776-4793

Pristine tropical forests play a critical role in regional and global climate systems. For a better understanding of the eco-hydrology of tropical “evergreen” vegetation, it is essential to know the partitioning of water into transpiration and evaporation, runoff and associated water ages. For this purpose, we evaluated how topography and vegetation influence water flux and age dynamics at high temporal (hourly) and spatial (10 m) resolution using the Spatially Distributed Tracer-Aided Rainfall-Runoff model for the tropics (STARRtropics). The model was applied in a tropical rainforest catchment (3.2 km²) where data were collected biweekly to monthly and during intensive monitoring campaigns from January 2013 to July 2018. The STARRtropics model was further developed, incorporating an isotope mass balance for evapotranspiration partitioning into transpiration and evaporation. Results exhibited a rapid streamflow response to rainfall inputs (water and isotopes) with limited mixing and a largely time-invariant baseflow isotope composition. Simulated soil water storage showed a transient response to rainfall inputs with a seasonal component directly resembling the streamflow dynamics which was independently evaluated using soil water content measurements. High transpiration fluxes (max 7 mm/day) were linked to lower slope gradients, deeper soils and greater leaf area index. Overall water partitioning resulted in 65% of the actual evapotranspiration being driven by vegetation with high transpiration rates over the drier months compared to the wet season. Time scales of water age were highly variable, ranging from hours to a few years. Stream water ages were conceptualized as a mixture of younger soil water and slightly older, deeper soil water and shallow groundwater with a maximum age of roughly 2 years during drought conditions (722 days). The simulated soil water ages ranged from hours to 162 days and for shallow groundwater up to 1,200 days. Despite the model assumptions, experimental challenges and data limitation, this preliminary spatially distributed model study enhances knowledge about the water ages and overall young water dominance in a tropical rainforest with little influence of deeper and older groundwater.  相似文献   

End member and Bayesian mixing models consistently indicate near-surface flowpath dominance in a pristine humid tropical rainforest     

Christian Birkel  Alicia Correa Barahona  Clément Duvert  Sebastián Granados Bolaños  Andres Chavarría Palma  Ana Maria Durán Quesada  Ricardo Sánchez Murillo  Harald Biester 《水文研究》2021,35(4):e14153

The impacts of forest conversion on runoff generation in the tropics have received much interest, but scientific progress is still hampered by challenging fieldwork conditions and limited knowledge about runoff mechanisms. Here, we assessed the runoff generation, flow paths and water source dynamics of a pristine rainforest catchment in Costa Rica using end member mixing analysis (EMMA) and a Bayesian mixing model (MixSIAR). Geochemical tracer data collected over a 4-week field campaign were combined with tritium data used to assess potential deeper groundwater flow pathways to the perennial stream. The streamflow composition was best captured using three end-members, namely throughfall, shallow (5–15 cm) and deeper (15–50 cm) soil water. We estimated the end-member contributions to the main stream and two tributaries using the two mixing approaches and found good agreement between results obtained from EMMA and MixSIAR. The system was overwhelmingly dominated by near-surface sources, with little evidence for deeper and older groundwater as tritium-derived baseflow mean transit time was between 2.0 and 4.4 years. The shallow soil flow pathway dominated streamflow contributions in the main stream (median 39% and 49% based on EMMA and MixSIAR, respectively), followed by the deeper soil (32% and 31%) and throughfall (25% and 19%). The two tributaries had even greater shallow soil water contributions relative to the main stream (83% and 74% for tributary A and 42% and 63% for tributary B). Tributary B had no detectable deep soil water contribution, reflecting the morphology of the hillslope (steeper slopes, shallower soils and lower vegetation density compared to hillslope A). Despite the short sampling campaign and associated uncertainties, this study allowed to thoroughly assess runoff generation mechanisms in a humid tropical catchment. Our results also provide a first comparison of two increasingly used mixing models and suggest that EMMA and MixSIAR yield comparable estimates of water source partitioning in this tropical, volcanic rainforest environment.  相似文献   

Hydrologic impacts of subsurface drainage from the field to watershed scale          下载免费PDF全文

Ricardo Mantilla  Morgan Fonley  Nandita B. Basu 《水文研究》2017,31(17):3017-3028

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Magmatism coeval with lower Paleozoic shelf basins in NW-Argentina (Tastil batholith): Constraints on current stratigraphic and tectonic interpretations     

Fernando D. Hongn  José M. Tubía  Aitor Aranguren  Néstor Vegas  Ricardo Mon  Gregory R. Dunning 《Journal of South American Earth Sciences》2010,29(2):289-305

The Tastil batholith (Eastern Cordillera, NW Argentina) holds relevant keys for interpreting the tectonic evolution of the Central Andes basement since it has always been interpreted as the subcrop of the Cambrian and Lower Ordovician basins in the Eastern Cordillera. However, in the Angosto de la Quesera section, the batholith intrudes sandstones underlying a fossiliferous Lower Tremadocian conglomerate containing Tastil granite pebbles. The precise assignation of the sandstones intruded by the granite to Cambrian Mesón Group or to the Uppermost Cambrian–Lower Tremadocian Santa Victoria Group is a key for refining the relationships between magmatic and sedimentary units. The ages of 526 Ma and 517 Ma (U/Pb, zircons) obtained from two facies of the batholith are coherent with the proposal of including these sandstones in the Mesón Group. However, the lithologic features and fossil content point to an affinity with the basal units of the Santa Victoria Group according to sedimentologic and stratigraphic studies ruled out by other authors. The intrusive relationships between the Tastil batholith and the Lower Paleozoic sandstones indicates the batholith is coeval with the Mesón and/or Santa Victoria groups basins instead of being its subcrop, which strongly contradicts previous proposals about basement evolution along the Lower Paleozoic margin of Gondwana. Therefore, the genesis and emplacement of the Tastil batholith must be related to the development of the Lower Paleozoic shelf basins rather than with the final stages of Puncoviscana-type basin evolution. The basement of central and northern Argentina records a wide spectrum of sedimentary, deformational, magmatic and metamorphic processes at a variety of crust levels during the Early Paleozoic. Tastil batholith emplacement and exhumation in the Eastern Cordillera represent shallower crustal expressions of the plutonic and high-T–low-P metamorphic events at deeper levels in the basement now exposed mainly in eastern Puna and Pampean Ranges.  相似文献   

Daily near-surface large-scale atmospheric circulation patterns over the wider Caribbean     

Xsitaaz T. Chadee  Ricardo M. Clarke 《Climate Dynamics》2015,44(11-12):2927-2946

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Uppermost Lower Aptian transgressive records in Mexico and Spain: chronostratigraphic implications for the Tethyan sequences     

Josep A. Moreno‐Bedmar  Telm Bover‐Arnal  Ricardo Barragán  Ramon Salas 《地学学报》2012,24(4):333-338

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The Bazar Ophiolite of NW Iberia: a relic of the Iapetus–Tornquist Ocean in the Variscan suture     

Sonia S. Martínez  Axel Gerdes  Ricardo Arenas  Jacobo Abati 《地学学报》2012,24(4):283-294

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Land–ocean distribution of allochthonous organic matter in surface sediments of the Chiloé and Aysén interior seas (Chilean Northern Patagonia)     

Nelson Silva  Cristian A. Vargas  Ricardo Prego 《Continental Shelf Research》2011,31(3-4):330-339

We investigated the relative distribution of allochthonous (i.e., terrigenous) organic matter in the complex, continuous, river–fjord–sound–channel–gulf system of Chile’s North Patagonia (41.5–46.5°S) in order to establish whether this organic matter can reach the open ocean or whether it is largely retained near its fluvial sources. Grain size distribution, total organic carbon and total nitrogen contents, and carbon stable isotope contents (δ¹³C) were quantified in 53 surface sediment samples collected during the CIMAR Fiordos cruises 1, 4, 8, and 10, as were salinity and silicic acid concentrations in the surface waters. A principal component analysis segregated the Chiloé and Aysén interior seas into two zones: (i) the continental fjords, with sediment enriched in allochthonous organic matter, having higher C:N molar ratios (10–14) and lower δ¹³C composition (?23‰ to ?27‰); and (ii) the channels and gulfs, with a prevalent autochthonous marine source, having lower C:N values (6–10) and higher δ¹³C composition (?20‰ to ?23‰). Estuarine waters with low salinity (2–30) and high silicic acid (10–90 μM) were associated with high C:N ratios and low δ¹³C in surface sediments, meaning that terrestrial organic matter was transported up to the mouth of the continental fjords. A two-source mixing model confirmed that allochthonous (terrestrial) organic matter contents (50–90%) associated with local river discharges were present within the continental fjords. On the contrary, autochthonous (marine) organic matter was prevalent (50–90%) at the sites in the marine influenced channels, sounds, and gulfs.  相似文献