Spatially distributed tracer‐aided modelling to explore water and isotope transport,storage and mixing in a pristine,humid tropical catchment          下载免费PDF全文

Joni Dehaspe  Christian Birkel  Doerthe Tetzlaff  Ricardo Sánchez‐Murillo  Ana María Durán‐Quesada  Chris Soulsby 《水文研究》2018,32(21):3206-3224

Rapidly transforming headwater catchments in the humid tropics provide important resources for drinking water, irrigation, hydropower, and ecosystem connectivity. However, such resources for downstream use remain unstudied. To improve understanding of the behaviour and influence of pristine rainforests on water and tracer fluxes, we adapted the relatively parsimonious, spatially distributed tracer‐aided rainfall–runoff (STARR) model using event‐based stable isotope data for the 3.2‐km² San Lorencito catchment in Costa Rica. STARR was used to simulate rainforest interception of water and stable isotopes, which showed a significant isotopic enrichment in throughfall compared with gross rainfall. Acceptable concurrent simulations of discharge (Kling–Gupta efficiency [KGE] ~0.8) and stable isotopes in stream water (KGE ~0.6) at high spatial (10 m) and temporal (hourly) resolution indicated a rapidly responding system. Around 90% of average annual streamflow (2,099 mm) was composed of quick, near‐surface runoff components, whereas only ~10% originated from groundwater in deeper layers. Simulated actual evapotranspiration (ET) from interception and soil storage were low (~420 mm/year) due to high relative humidity (average 96%) and cloud cover limiting radiation inputs. Modelling suggested a highly variable groundwater storage (~10 to 500 mm) in this steep, fractured volcanic catchment that sustains dry season baseflows. This groundwater is concentrated in riparian areas as an alluvial–colluvial aquifer connected to the stream. This was supported by rainfall–runoff isotope simulations, showing a “flashy” stream response to rainfall with only a moderate damping effect and a constant isotope signature from deeper groundwater (~400‐mm additional mixing volume) during baseflow. The work serves as a first attempt to apply a spatially distributed tracer‐aided model to a tropical rainforest environment exploring the hydrological functioning of a steep, fractured‐volcanic catchment. We also highlight limitations and propose a roadmap for future data collection and spatially distributed tracer‐aided model development in tropical headwater catchments.  相似文献   

Modelling infiltration enhancement in a tropical urban catchment for improved stormwater management   总被引：1，自引：0，他引：1       下载免费PDF全文

Ting Fong May Chui  Dieu Huong Trinh 《水文研究》2016,30(23):4405-4419

To mitigate the impacts of impervious surfaces in urban areas, structures such as bioretention systems and permeable pavements have been installed to enhance infiltration in many countries. However, relatively little knowledge is available regarding the performance of such infiltration‐based structures in humid tropical and highly urbanized areas. This study investigates the feasibility of enhancing the infiltration of stormwater in tropical urbanized areas using Singapore as a case study. It first shows that the rainfall depth and intensity are both high, but the time interval between consecutive rainfall event is long in Singapore. It then numerically simulates single‐event local infiltration and finds that the fraction of infiltrated rainfall is actually high. It finally performs catchment‐scale simulations and finds that bioretention systems can enhance infiltration and groundwater recharge particularly during wet periods. However, local mounding of groundwater can be significant and can hinder the performance of those structures. Furthermore, with 5% of catchment area being converted to such structures, the infiltration of the entire catchment is enhanced but still not yet up to the natural level. To increase the overall effectiveness, future studies can look into bioretention systems with underdrain systems. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Linking tracers,water age and conceptual models to identify dominant runoff processes in a sparsely monitored humid tropical catchment          下载免费PDF全文

Christian Birkel  Chris Soulsby 《水文研究》2016,30(24):4477-4493

Assessing catchment runoff response remains a key research frontier because of limitations in current observational techniques to fully characterize water source areas and transit times in diverse geographical environments. Here, we report a study that combines empirical data with modelling to identify dominant runoff processes in a sparsely monitored humid tropical catchment. The analysis integrated isotope tracers into conceptual rainfall–runoff models of varying complexity (from 5 to 11 calibrated parameters) that are able to simulate discharge and tracer concentrations and track the evolving age of stream water exiting the catchment. The model structures can be seen as competing hypotheses of catchment functioning and were simultaneously calibrated against uncertain streamflow gaugings and a 2‐year daily isotope rainfall–runoff record. Comparison of the models was facilitated using global parameter sensitivity analysis and the resulting effect on calibration. We show that a variety of tested model structures reproduced water and tracer dynamics in stream, but the simpler models failed to adequately reproduce both. The resulting water age distributions of the tested models varied significantly with little similarity between the stream water age and stored water age distributions. The sensitivity analysis revealed that only some of the more complex models (from eight parameters) could be better constrained to infer more plausible water age distributions and catchment storage estimates. These models indicated that the age of water stored in the catchment is generally older compared with the age of water fluxes, with evapotranspiration age being younger compared with streamflow. However, the water age distributions followed a similar temporal behaviour dominated by climatic seasonality. Stream water ages increased during the dry season (greater than 1 year) and decreased with increased streamflow (a few weeks old) during the wet season. We further show that the ratios of the streamwater age to stored water age distribution and the water age distribution of actual evapotranspiration to the stored water age distribution from constrained models could potentially serve as useful hydrological indicators of catchment functioning. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Patterns of mixed siliciclastic‐carbonate sedimentation adjacent to a large dry‐tropics river on the central Great Barrier Reef shelf,Australia     

《Australian Journal of Earth Sciences》2013,60(5):665-683

The Great Barrier Reef represents the largest modern example of a mixed siliciclastic‐carbonate system. The Burdekin River is the largest source of terrigenous sediment to the lagoon and is therefore an ideal location to investigate regional patterns of mixed sedimentation. Sediments become coarser grained and more poorly sorted away from the protection of eastern headlands, with mud accumulation focused in localised ‘hot spots‘ in the eastern portion of embayments protected from southeast trade winds. The middle shelf has a variable facies distribution but is dominated by coarse carbonate sand. North of Bowling Green Bay, modern coarse carbonate sand and relict quartzose sand occur. Shore‐normal compositional changes show Ca‐enrichment and Al‐dilution seawards towards the reef, and shore‐parallel trends show Al‐dilution westwards (across bays) along a Ca‐depleted mixing line. Intermediate siliciclastic‐carbonate sediment compositions occur on the middle shelf due to the abundance of relict terrigenous sand, a pattern that is less developed on the narrow northern Great Barrier Reef shelf. Rates of sediment deposition from seismic evidence and radiochemical tracers suggest that despite the magnitude of riverine input, 80–90% of the Burdekin‐derived sediment is effectively captured in Bowling Green Bay. Over millennial time‐scales, stratigraphic controls suggest that sediment is being preferentially accreted back to the coast.  相似文献   

Tropical Marine Fungi*     

Jan Kohlmeyer 《Marine Ecology》1984,5(4):329-378

Abstract. Marine Ascomycetes, Basidiomycetes and Deuteromycetes were collected in tropical and subtropical regions (Australia, Belize, Fiji, Hawaii, Marshall Islands, Mexico, New Zealand, Palau, Thailand), and the known range of distribution for these fungi was extended. Exclusively tropical are 27 taxa, 9 are probably restricted to the tropics also, and 11 are cosmopolitan. Distribution maps are given for 5 taxa. New species (4), varieties (3), and combinations (2) of Ascomycetes are proposed, and keys to the taxa of Halosarpheia and Lulworthia are presented. Most of the species are decomposers of mangrove parts or of detritus in sandy beaches. Nine new host plants were found. Marine Ascomycetes were discovered for the first time living in shells of foraminifera.  相似文献   

Preliminary spectral characterization of snow in a high altitude tropical glacier and potential effects of impurities in snow on albedo of tropical glaciers     

Jean Emmanuel Sicart  Yves Arnaud 《水文研究》2007,21(26):3642-3644

This paper presents some preliminary measurements of snow spectral reflectance on the tropical Bolivian Zongo glacier. Measurements show a correct agreement with theoretical spectral albedo of pure snow in the near infrared region, but lower values in the visible region (by 10–20%) probably due to aerosols contained in snow. Impurity contents ranged from 10 to 100 ppmw in one‐week‐old snow collected from the Zongo glacier, but measurements are scarce. Large amounts of snowfall partly compensate the proximity of dust sources in mid‐latitude glaciers, whereas on outer‐tropical glaciers precipitations are not abundant and are very seasonal, and sources of aerosols are proximate. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

The generation and redistribution of overland flow on a massive oxic soil in a eucalypt woodland within the semi-arid tropics of North Australia     

Mike Bonell  John Williams 《水文研究》1986,1(1):31-46

There is a dearth of knowledge on the runoff processes of eucalypt woodland communities in the semi-arid tropics of Australia. The work was undertaken on a 100 m transect of a 0·8 degree hillslope typical of the ‘smooth plainlands’ of central-north Queensland. This paper introduces a new experimental design for measuring overland flow in such areas by way of a cascade system of unbounded runoff plots which allow the inputs and outputs between troughs to be calculated. Most storms generate overland flow. Time to overland flow ranges between 1 and 18 min where rain intensities are above 10mm hr⁻¹ and when the average detention storage of 3·6 mm is exceeded. The bare soil surfaces within the scattered grass understory control the runoff generation process through the temporal variability of field saturated hydraulic conductivity. The study demonstrated that overland flow is mainly redistributed over the freely-draining oxic soil. Some areas export more overland flow than they gain from upslope (runoff), others gain more overland flow than they export (runon). Over the study period only 2 per cent of total rain is transferred out of this 100 m transect as overland flow due to the short duration of storms, the relatively high soil permeability, and the low slope angle. The remainder adds to the large soil water store or deep drainage. The variability of runoff–runon over these ‘smooth plainlands’ highlights how results from bounded plots would be misleading in such areas.  相似文献   

食物浓度对模糊秀体溞生长和繁殖的影响   总被引：1，自引：1，他引：0       下载免费PDF全文

尹娟  韩博平 《湖泊科学》2008,20(3):344-350

模糊秀体潘是热带水体中枝角类的主要优势种，它在竞争及对热带水体的适应方面的优势尚不清楚。本文以模糊秀体潘为研究对象，观察不同食物浓度下其生长和繁殖的特点，探讨模糊秀体潘成热带水体优势种的原因。以蛋白核小球藻为食物，浓度梯度设为0.05mg／L、0.1mg／L、0.3mg／L、0.6mg／L和1.0mg／L小球藻浓度为0.05mg／L的培养液中，模糊秀体潘存活率很低且未观察到繁殖现象其它4个浓度小球藻喂养的模糊秀体潘体长生长率和最大体长均随食物浓度的升高而增加，最大体长分别达到1.087mm、1.125mm、1.225mm、1.313mm；食物浓度对模糊秀体溢的胚胎发育时间，平均寿命，个体累计产幼数无显著影响：随着食物浓度的升高，模糊秀体滏初次怀卵体长显著增加，繁殖前期的历时相应缩短，平均每胎产幼数增加：内禀增长率随食物浓度升高而增大，达到0.6mg／L后比较稳定。浓度为0.6mg／L时，模糊秀体潘的净生殖率也达到最大值。1.0mg／L组的世代时间最短，内禀增长率接近最大值。0.6mg／L和1.0mg／L为模糊秀体潘生长比较适宜的食物浓度。热带自然水体中，模糊秀体潘相对其它浮游动物个体小和怀卵率低的现象并非食物不足所致；食物充足条件下的最大成体的个体大小与野外样品接近，也说明自然水体中捕食并没有显著影响成体的个体大小。模糊秀体潘体型较小、身体透明、行动敏捷，容易逃避鱼类的捕食，可能是模糊秀体潘能在食物丰富的热带水体中，特别是透明度较低的富营养化湖泊中能够成为枝角类中优势种的主要原因。  相似文献   

Characteristics of rain events at an inland locality in northeastern Borneo,Malaysia     

Kawi Bidin  Nick A. Chappell 《水文研究》2006,20(18):3835-3850

Understanding the intensity and duration of tropical rain events is critical to modelling the rate and timing of wet‐canopy evaporation, the suppression of transpiration, the generation of infiltration‐excess overland flow and hence to erosion, and to river responsiveness. Despite this central role, few studies have addressed the characteristics of equatorial rainstorms. This study analyses rainfall data for a 5 km² region largely comprising of the 4 km² Sapat Kalisun Experimental Catchment in the interior of northeastern Borneo at sampling frequencies from 1 min^?1 to 1 day^?1. The work clearly shows that most rainfall within this inland, forested area is received during regular short‐duration events (<15 min) that have a relatively low intensity (i.e. less than two 0·2 mm rain‐gauge tips in almost all 5 min periods). The rainfall appears localized, with significant losses in intergauge correlations being observable in minutes in the case of the typical mid‐afternoon, convective events. This suggests that a dense rain‐gauge network, sampled at a high temporal frequency, is required for accurate distributed rainfall‐runoff modelling of such small catchments. Observed rain‐event intensity is much less than the measured infiltration capacities, and thus supports the tenet of the dominance of quick subsurface responses in controlling river behaviour in this small equatorial catchment. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

From vulnerability to immunization—A genealogy of early attempts to deal with the climate          下载免费PDF全文

Tim Frewer 《Singapore journal of tropical geography》2016,37(1):43-58

In an age of anthropogenic climate change, risk and vulnerability have become common parlance. Yet the histories of both concepts are bound up in the colonial project. This article attempts to give a brief genealogy of these concepts by considering their evolution within early colonial attempts to deal with the dangers and threats posed by a tropical climate. This article argues that British and French colonial writers and administrators began to understand the dangers associated with colonizing distant lands as distinct risks associated with living in a tropical climate. Tropical fevers, ecological devastation, famine and revolt in particular spurred on the development of new knowledge, which advanced understandings of the effects of the tropical climate both on European health and long‐term colonial ambitions. In turn the concept of a pernicious tropical climate that posed a biological threat to the health of Europeans came to play a major role in configuring prevailing notions of race, health and morality. Risk and vulnerability have been key discursive features of new knowledges and governmental technologies crafted in the context of colonialism to secure European rule over distant lands and people.  相似文献