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Ítem Optimizing social-ecological analysis of coupled human-river systems through the integration of conceptual frameworks: The case of the Savegre watershed, Costa Rica(Universidad Nacional de Costa Rica, 2018-11-22) Espinoza Cisneros, EdgarSocial-ecological systems, given their immanent complexity and unpredictability, pose intricate management challenges. Conceptual/analytical frameworks that more holistically integrate coupled social and natural systems and their basic interdependencies and interactions can significantly improve management and research efforts at multiple levels, specifically by accounting for the complex, multi-scalar processes involved, including the dynamics of distal and more proximate causal factors, as well as how they manifest and evolve in space and time. This paper presents a synthesis from a social-ecological analysis of the Savegre river watershed in Costa Rica, a recently designated UNESCO Biosphere Reserve. Through this exercise, the watershed is conceptualized as a coupled social-ecological system, with complex interconnections among social, ecological and physical components, for developing research agendas or specific normative efforts. Syntheses like the one presented here are particularly useful for more in-depth explorations of social-ecological issues, especially collective action problems derived from human-environment interactions at various scales. More effective formal and informal normative solutions to pressing sustainability dilemmas can also be envisioned through similar exercises.Ítem Evaluación espaciotemporal del cambio global en el Departamento Sur de Haití, de 1973 al 2017(Universidad de Cuenca, 2019-12-18) Espinoza Cisneros, Edgar; Martínez Martínez, Marco; Birkel Dostal, Christian; Lizano Araya, Melvin Arnoldo; Phillipe, Edes; Benegas Negri, Laura AndreaHaiti as a country faces great environmental and societal challenges. Haiti is characterized by a high deforestation, lack of territorial planning, political and economic instability, and a growing population exerting pressure on natural resources. In this article, we analyze the historic land cover change in the Southern Department of Haiti from 1973 to 2017 and the relationship to socioeconomic and biophysical variables. All variables under change together are considered as the holistic definition of global change. We used Landsat satellite images, public data repositories and statistical correlations to analyze the directionality of the above-mentioned global change in Haiti. The results showed a marked fluctuation of crop areas, a relation of bare soil with deforested areas, as well as a decrease in forest cover after a series of hydrometeorological and sociopolitical events. In addition, we found that changes in brush area were significantly associated with the rates of change in population, temperature and the Human Development Index (HDI), while the rate of change in rainfall significantly influenced the change in crop coverage. On the other hand, changes in bare soil had a significant relationship with the rate of population change. Finally, none of the variables considered was significantly correlated with the spatiotemporal change of urban and forest coverage.Ítem Metodologías participativas aplicadas a la socio-hidrología y su potencial para la incidencia social: algunas reflexiones(Universidad de Costa Rica, 2020-05-26) Espinoza Cisneros, Edgar; Blanco Ramírez, SaraIntroducción y objetivo: En el marco de las II Jornadas de Investigación de la Facultad de Ciencias Sociales de la Universidad de Costa Rica (UCR), este artículo examina el potencial de incidencia social de metodologías participativas para la gestión ambiental, especialmente en el campo emergente de la socio-hidrología. Para ello, nos apoyamos en dos proyectos de investigación que actualmente están en desarrollo y que pretenden incidir en la toma de decisiones en diversos niveles de gobernanza.Ítem Dinámicas socioambientales contemporáneas y las nuevas oportunidades para realzar la geografía latinoamericana(Project MUSE, 2020) Espinoza Cisneros, Edgar; Avendaño Flores, María IsabelComo parte de las reflexiones en torno a los 50 años de la Conferencia de Geografía Latinoamericana, argumentamos que la geografía está ante una coyuntura mundial y regional propicia para realzar su capacidad de contribuir al cambio social y, con ello, procurar una mayor presencia en círculos académicos, profesionales y políticos. Para ello, primero expusimos algunas tendencias conceptuales y metodológicas interdisciplinarias muy ligadas a la geografía que buscan abordar estos desafíos socioambientales y que están siendo incorporadas en estructuras de toma de decisiones. Luego resaltamos el rol de una educación geográfica que incorpore estas tendencias como una vía para el (re)posicionamiento de la geografía como una ciencia vital para el cambio social. Soluciones efectivas a los retos de alcance global que enfrentamos a nivel regional requieren imprescindiblemente de los aportes de la geografía, pero depende de nosotros los geógrafos hacerlo ver y valer. Por eso, nuestros esfuerzos deben concentrarse en recuperar la posición de privilegio que por mucho tiempo tuvimos como ciencia normativa, algo que James Parsons exhortaba en esta misma revista hace casi 50 años.Ítem Relaciones sociedad-naturaleza y la pandemia del COVID-19: ¿vaso medio lleno o medio vacío?(Universidad de Costa Rica, 2020-06-04) Espinoza Cisneros, EdgarLas crisis, en muchos casos, impulsan cambios que marcan la evolución de las sociedades humanas. Esto ha aplicado en las relaciones sociedad-naturaleza, a través de un vínculo de realimentación donde las crisis determinan estas relaciones y viceversa. En este ensayo se reflexiona sobre algunas posibles avenidas de acción que se pueden tomar hacia sociedades más resilientes y sostenibles, motivadas por la pandemia del COVID-19. Además, se examina brevemente esa relación entre enfermedades infecciosas y acciones humanas sobre el ambiente, así como algunas iniciativas que se promueven actualmente para engendrar cambios sociales hacia la sostenibilidad a raíz de la crisis por la pandemia.Ítem Desarrollo e implementación de un sistema de información geográfica para la gestión y administración del patrimonio cultural de los centros históricos: El caso del Centro Histórico de la ciudad de Limón(2023-06) Guevara Murillo, Mauricio; Malavassi Aguilar, Rosa ElenaEl presente trabajo constituye el resultado de la Práctica de Especialidad de la Maestría en Sistemas de Información Geográfica y Teledetección del programa interinstitucional entre la Universidad de Costa Rica y la Universidad Nacional. El mismo tuvo por objeto implementar las herramientas SIG en los procesos de administración, control, puesta en valor y difusión de los recursos patrimoniales para medir su potencial en la mejora de los procesos. Metodológicamente se desarrolló un proceso de investigación aplicada que buscó dar una solución técnica a una entidad encargada de la gestión y puesta en valor de los recursos patrimoniales en el territorio de la Ciudad de Limón. La solución se centró en la articulación de una base de datos geoespacial para el archivo del inventario de bienes patrimoniales del territorio y un portal web para la difusión de los principales hallazgos respecto de los recursos patrimoniales y base para la toma de decisiones. La propuesta se articula con el proyecto de extensión, “Aprovechamiento de oportunidades para la generación de desarrollo endógeno mediante la puesta en valor de recursos patrimoniales en el Casco histórico y primer ensanche de la ciudad de Limón” del Instituto Tecnológico de Costa Rica mismo que requiere una aplicación SIG que permita sistematizar los resultados de su investigación en una herramienta que permita dar seguimiento al estado de los recursos patrimoniales y articularlos con una estrategia de gestión para aprovechamiento y puesta en valor. La implementación de la base de datos espacial permite gestar una herramienta no sólo para la integración de la información de los bienes patrimoniales y los diferentes elementes espaciales y no espaciales vinculados a ellos, sino además para el análisis de datos y la generación de datos para una toma de datos fundamentada. Por su parte el desarrollo del sitio web permite una difusión universal de los recursos, repercutiendo en su difusión y puesta en valor, al mismo tiempo se convierte en el espacio para consulta de datos que permitan una toma de decisiones objetiva y coherente con la situación de los recursos del patrimonio cultural. Finalmente, el desarrollo e implementación del Sistema de Información Geográfica demuestra que existe el potencial para implementar estas herramientas en la administración y gestión de los recursos patrimoniales, para llevar el desarrollo tecnológico y el abordaje de patrimonio cultural a la altura del desarrollo internacional en esta materia.Ítem Propuesta metodológica para el análisis espacial de las relaciones entre valores y acciones de conservación del agua y el rol de factores externos en sistemas funcionalmente interdependientes: el caso de la cuenca del Savegre, Costa Rica(2017) Espinoza Cisneros, ÉdgarEstudios recientes concuerdan que es cada vez mayor el nivel de concientización de la gente a nivel mundial en torno a varias problemáticas ambientales, pero sin embargo no se ha correspondido con acciones individuales y voluntarias que remedien esos problemas. Esta discrepancia entre lo que se piensa y lo que se hace es conocida como la brecha entre valores y acciones o entre actitudes y conductas, y ha sido explorada mayormente desde la rama de la psicología ambiental. Muchos factores intervienen en la generación de estas brechas, tanto internos (psicológicos) como externos (contextuales), y éstos últimos, a pesar de su reconocida influencia en inhibir o propiciar acciones pro-ambientales, han sido poco explorados por las ciencias sociales. Esta ponencia propone un abordaje metodológico que integra aportes de la psicología social y ambiental con la perspectiva crítico-analítica de la geografía, con el fin de entender mejor las dimensiones espaciales de estas discrepancias cognitivo-conductuales y el rol que juegan estos los factores externos en generar dichas discordancias para el caso de acciones de conservación y protección del agua. Esto se propone llevar a cabo en un sistema funcionalmente interdependiente como una cuenca hidrográfica, dado que dicho conocimiento podría tener importantes implicaciones en el diseño de estrategias para la sostenibilidad en estos sistemas con alta conectividad.Ítem “Walking the talk” in land management: Structural factors influencing pro-environmental intention-action links in a tropical watershed(Elsevier BV, 2020-10) Espinoza Cisneros, Edgar; Akhter, MajedIn this paper, we examine structural factors conditioning the adoption of pro-environmental practices in land management. While the thinking-action relationship has been widely studied in psychology, there is a need to further investigate, from a geographical perspective, how structure shortens or widens the gap between pro-environmental intentions and actions in land management. In filling this need, we examine the structural factors reported to influence this intention-action link in a Costa Rican watershed recently designated a UNESCO Biosphere Reserve for its social-ecological importance. To this end, we draw on intensive fieldwork and land manager interview data. Research design was informed by theoretical and conceptual insights from social psychology, land systems science and political ecology. Results suggest a strong influence of diverse structural factors on the pro-environmental intention-action connection in land use in this social-ecological system, both as a facilitating and/or constraining force. More salient is the marked gap between intentions and actions among managers, largely influenced by market dynamics and incentive structures, land tenure policies, perceptions about government institutional performance, and deficient extension networks. These results highlight the need to “clear the way” for pro-environmental intentions to materialize into actions through selective structural measures, especially in social-ecological landscapes facing dire needs to reduce ecological impacts of productive systems.Ítem Exploratory radioisotope measurements suggest that in‑stream erosion represents the main sediment source in a pristine, tropical rainforest in Costa Rica(2022-09-05) Birkel Dostal, Christian; Duvert, Clément; Vargas Arias, Katherine; Walling, Desmond E.; Cubero Campos, Mario AlbertoPurpose. Volcanic, humid tropical landscapes are characterized by short-term geomorphic transformations due to volcanism and seismic activity, landslides, and other frequent mass movements. These landscape-forming processes are amplifed by high temperatures, high annual precipitation rates, and intense rainstorms. The latter can result in signifcant surface runoff and sediment mobilization, even under pristine rainforest cover. However, knowledge about sediment sources and the mag nitude of the associated erosion and accumulation rates remains limited in these systems. Methods. This study explores the use of radioisotopes (U-235, Bi-214, Pb-214, total Pb-210, and K-40) and of the fallout radionuclide (FRN) Cs-137 to address that knowledge gap in a pristine, tropical rainforest catchment in northern Costa Rica. We analyzed FRN and radioisotope activities from two reference soil profles and compared them with those of 17 superfcial soil samples collected on two hillslopes and of three streambed sediment samples. Results. Modeled hillslope erosion and accumulation rates ranged from 6 t ha−1 year−1 erosion to 6.7 t ha−1 year−1 deposition with up to±60% uncertainty refecting spatially variable interception of rainfall inputs. Preliminary sediment fngerprint ing results suggested that deeper soil material, likely originating from in-stream bank erosion and channel incision, was the dominant source of stream sediment (79±19%), whereas superfcial soil present on the hillslopes only contributed 22±18% to the stream mixture. Conclusion. Our exploratory work highlights the potential importance of channel erosion processes in the sediment yield of steep rainforest catchments, even when hillslopes and streams have a strong hydrological connection.Ítem Developing a model to assess the impact of farm dams and irrigation for data-scarce catchments(2024-04-15) Watson, Andrew Paul; Künne, Annika; Birkel Dostal, Christian; Miller, Jodie A.; Kralisch, SvenProductive agricultural supply chains require the support of functional ecosystems, but intense agricultural practices change local hydrological systems (e.g. river diversion). In this study, the impact of farm dams was assessed for the Verlorenvlei catchment, a sensitive ecosystem currently under a state of hydrological change in South Africa. We developed a new module for the Jena Adaptable Modelling System (JAMS)/J2000 rainfall–runoff model to assess the streamflow impact from the points of abstraction, losses during storage and irrigation. The model achieved a satisfactory streamflow calibration with efficiencies Nash Sutcliffe Efficiency (NSE, logNSE) of 0.52 and 0.51. The irrigated area reduced simulated streamflow by 12 to 19%. The results from the study agree with remote sensed evapotranspiration, measured lake surface water levels and streamflow, but uncertainty remains in the total simulated dam evaporation. While many catchments lack the data required for a detailed irrigation impact assessment, this approach considers total water use, dam storage to area relationships and general farming practices.Ítem Tracer-aided ecohydrological modelling across climate, land cover, and topographical gradients in the tropics(2023-05-01) Arciniega Esparza, Saúl; Birkel Dostal, Christian; Durán Quesada, Ana María; Sánchez Murillo, Ricardo; Moore, Georgianne W.; Maneta, Marco P.; Boll, Jan; Benegas Negri, Laura Andrea; Tetzlaff, Doerthe; Yoshimura, Kei; Soulsby, ChrisQuantitative estimations of ecohydrological water partitioning into evaporation and transpiration remains mostly based on plot-scale investigations that use well-instru mented, small-scale experimental catchments in temperate regions. Here, we attempted to upscale and adapt the conceptual tracer-aided ecohydrology model STARRtropics to simulate water partitioning, tracer, and storage dynamics over daily time steps and a 1-km grid larger-scale (2565 km2) in a sparsely instrumented tropical catchment in Costa Rica. The model was driven by bias-corrected regional climate model outputs and was simultaneously calibrated against daily discharge observations from 2 to 30 years at four discharge gauging stations and a 1-year, monthly stream water isotope record of 46 streams. The overall model performance for the best dis charge simulations ranged in KGE values from 0.4 to 0.6 and correlation coefficients for streamflow isotopes from 0.3 to 0.45. More importantly, independent model derived transpiration estimates, point-scale residence time estimates, and measured groundwater isotopes showed reasonable model performance and simulated spatial and temporal patterns pointing towards an overall model realism at the catchment scale over reduced performance in the headwaters. The simulated catchment system was dominated by low-seasonality and high precipitation inputs and a marked topo graphical gradient. Climatic drivers overrode smaller, landcover-dependent transpira tion fluxes giving a seemingly homogeneous rainfall-runoff dominance likely related to model input bias of rainfall isotopes, oversimplistic Potential Evapotranspiration (PET) estimates and averaged Leaf Area Index (LAI). Topographic influences resulted in more dynamic water and tracer fluxes in the headwaters that averaged further downstream at aggregated catchment scales. Modelled headwaters showed greater storage capacity by nearly an order of magnitude compared to the lowlands, which also favoured slightly longer residence times (>250 days) compared to superficially well-connected groundwater contributing to shorter streamflow residence times (<150 days) in the lowlands. Our findings confirm that tracer-aided ecohydrological modelling, even in the data-scarce Tropics, can help gain a first, but crucial approxi mation of spatio-temporal dynamics of how water is partitioned, stored and transported beyond the experimental catchment scale of only a few km2.Ítem Spatio-temporal visualization of soil dissolved organic carbon production and mobilization in a high-elevation Andean catchment(2024-06-17) Pesántez, Juan Pablo; Birkel Dostal, Christian; Guamán, Stalin; Jerves Ramírez, Mateo; Gaona Gaona, Gabriel Vicente; Arciniega Esparza, Saúl; Murray, Desneiges S.; Célleri Alvear, Rolando; Crespo, Patricio JavierThe visualization of dissolved organic carbon (DOC) spatial patterns can be a valuable tool for a comprehensive understanding of DOC production and transport processes within a catchment (Birkel et al., 2017; Pesántez, Birkel, Mosquera, et al., 2023; Wu et al., 2014). Visualizations of catchment fluxes, storages, and water ages, for instance, have already provided a key technique for enhancing our understanding of hydrological catchment functioning in various eco systems (Smith et al., 2022; Van Huijgevoort et al., 2016b). The Spa tially Distributed Tracer-Aided Rainfall-Runoff Model (STARR) offers the opportunity to represent hydrological processes, but also to incor porate tracers for validating hydrological processes (van Huijgevoort et al., 2016a), as highlighted below.Ítem Evaluating input data sources for isotope-enabled rainfall-runoff models(2024-09-20) Watson, Andrew Paul; Birkel Dostal, Christian; Arciniega Esparza, Saúl; de Waal, Jan; Miller, Jodie A.; Vystavna, Yuliya; van Rooyen, Jared; Welham, Angela; Bong, Hayoung; Yoshimura, Kei; Helmschrot, Jörg; Künne, Annika; Kralisch, SvenIsotope-enabled models provide a means to generate robust hydrological simulations. However, daily isotope-enabled rainfall-runoff models applied to larger spatial scales (>100 km2) require more input data than conventional non-isotope models in the form of precipitation isotope time series, which are difficult to generate even with point station measurements. Spatially distributed isotope data can be circumvented by isotope enabled climate models. Here, we evaluate the hydrological simulations of the J2000-isotope enabled hydrological model driven with data from corrected and un-corrected isotope-enabled global and regional climate models (isotope-enabled global spectral model [IsoGSM] and isotope-enabled regional spectral model [IsoRSM], respectively) compared with 1 year of measured reference station and a yearly average precipitation isotope input for a pilot site, the data-scarce sub-humid Eerste River catchment in South Africa. The models driven by all input products per formed well for upstream and downstream discharge gauges with Nash Sutcliffe effi ciency (NSE) from 0.58 to 0.85 and LogNSE of 0.66 to 0.93. The simulated δ2H stream isotopes using the reference J2000-iso and J2000-isoRSM were good for the main river with a stream Kling Gupta efficiency (KGE) of between 0.4–0.9 and the top 100 Monte Carlo simulations varying by around 5‰ for δ2H. For smaller tribu taries the model was unable to capture the measured stream isotopes due to biased precipitation isotope inputs. Adjusting the J2000-iso with a bias corrected IsoRSM improved the stream and groundwater isotope simulation and outperformed the model driven by an average yearly precipitation isotope input. Differences in simu lated hydrological processes were only evident between the models when evaluating percolation with unrealistic simulations for the standard J2000 model. While the regional climate model is computationally more intensive than its global counterpart, it provided better stream isotope simulations and improvements to simulated perco lation. Our results indicate that isotope-enabled climate models can provide useful input data in data scarce regions for hydrological models, where improved water management to address climate change impacts is needed.Ítem Seasonal wetlands make a relatively limited contribution to the dissolved carbon pool of a lowland headwater tropical stream(2024-02-07) Solano Rivera, Vanessa; Duvert, Clément; Hutley, Lindsay Beaumont; Cendón, Dioni I.; Maher, Damien Troy; Birkel Dostal, ChristianWetlands process large amounts of carbon (C) that can be exported laterally to streams and rivers. However, our understanding of wetland inputs to streams remains unclear, particularly in tropical systems. Here we estimated the contribution of seasonal wetlands to the C pool of a lowland headwater stream in the Australian tropics. We measured dissolved organic and inorganic C (DOC and DIC) and dissolved gases (carbon dioxide—CO2, methane—CH4) during the wet season along the mainstem and in wetland drains connected to the stream. We also recorded hourly measurements of dissolved CO2 along a ‘stream–wetland drain–stream’ continuum, and used a hydrological model combined with a simple mass balance approach to assess the water, DIC and DOC sources to the stream. Seasonal wetlands contributed ∼15% and ∼16% of the DOC and DIC loads during our synoptic sampling, slightly higher than the percent area (∼9%) they occupy in the catchment. The riparian forest (75% of the DOC load) and groundwater inflows (58% of the DIC load) were identified as the main sources of stream DOC and DIC. Seasonal wetlands also contributed marginally to stream CO2 and CH4. Importantly, the rates of stream CO2 emission (1.86 g C s−1) and DOC mineralization (0.33 g C s−1) were much lower than the downstream export of DIC (6.39 g C s−1) and DOC (2.66 g g C s−1). This work highlights the need for further research on the role of riparian corridors as producers and conduits of terrestrial C to tropical streams.Ítem Process-informed subsampling improves subseasonal rainfall forecasts in Central America(2024-01-05) Kowal, Katherine M.; Slater, Louise J.; Li, Sihan; Kelder, Timo; Hall, Kyle J. C.; Moulds, Simon; García López, Alan Andrés; Birkel Dostal, ChristianSubseasonal rainfall forecast skill is critical to support preparedness for hydrometeorological extremes. We assess how a process-informed evaluation, which subsamples forecasting model members based on their ability to represent potential predictors of rainfall, can improve monthly rainfall forecasts within Central America in the following month, using Costa Rica and Guatemala as test cases. We generate a constrained ensemble mean by subsampling 130 members from five dynamic forecasting models in the C3S multimodel ensemble based on their representation of both (a) zonal wind direction and (b) Pacific and Atlantic sea surface temperatures (SSTs), at the time of initialization. Our results show in multiple months and locations increased mean squared error skill by 0.4 and improved detection rates of rainfall extremes. This method is transferrable to other regions driven by slowly-changing processes. Process-informed subsampling is successful because it identifies members that fail to represent the entire rainfall distribution when wind/SST error increases.Ítem Advancing isotope-enabled hydrological modelling for ungauged calibration of data-scarce humid tropical catchments(2024-02-11) Watson, Andrew Paul; Kralisch, Sven; Miller, Jodie A.; Vystavna, Yuliya; Gokool, Shaeden; Künne, Annika; Helmschrot, Jörg; Arciniega Esparza, Saúl; Sánchez Murillo, Ricardo; Birkel Dostal, ChristianRealistic projections of the future climate and how this translates to water availability is crucial for sustainable water resource management. However, data availability con strains the capacity to simulate streamflow and corresponding hydrological processes. Developing more robust hydrological models and methods that can circumvent the need for large amounts of hydro-climatic data is crucial to support water-related decisions, particularly in developing countries. In this study, we use natural isotope tracers in addition to hydro-climate data within a newly developed version of the spatially-distributed J2000iso as an isotope-enabled rainfall-runoff model simulating both water and stable isotope (δ2H) fluxes. We pilot the model for the humid tropical San Carlos catchment (2500 km2) in northeastern Costa Rica, which has limited time series, but spatially distributed data. The added benefit of sim ulating stable isotopes was assessed by comparing different amounts of observation data using three model calibration strategies (i) three streamflow gauges, (ii) three gauges with stream isotopes and (iii) isotopes only. The J2000iso achieved a stream flow Kling–Gupta efficiency (KGE) of 0.55–0.70 across all the models and gauges, but differences in hydrological process simulations emerged when including stable water isotopes in the rainfall-runoff calibration. Hydrological process simulation var ied between the standard J2000 rainfall-runoff model with a high simulated surface runoff proportion of 37% as opposed to the isotope version with 84%–89% simulated baseflow or interflow. The model solutions that used only isotope data for calibration exhibited differences in simulated interflow, baseflow and model perfor mance but captured bulk water balances with a reasonable match between the simu lated and observed hydrographs. We conclude that J2000iso has shown the potential to support water balance modelling for ungauged catchments using stable isotope, satellite and global reanalysis data sets.Ítem ENSO sentinels in the Americas' humid tropics: We need combined hydrometric and isotopic monitoring for improved El Niño and La Niña impact prediction(2023-12-17) Sánchez Murillo, Ricardo; Birkel Dostal, Christian; Boll, Jan; Esquivel Hernández, Germain; Rojas Jiménez, Luis David; Castro Chacón, Laura; Durán Quesada, Ana María; Voarintsoa, Ny Riavo Gilbertinie; Dee, Sylvia G.; Winguth, Arne M. E.This Scientific Briefing presents results from a nearly 10-year hydrometric and iso tope monitoring network across north-central Costa Rica, a region known as a headwater-dependent system. This monitoring system has recorded different El Niño and La Niña events and the direct/indirect effects of several hurricane and tropical storm passages. Our results show that El Niño-Southern Oscillation (ENSO) exerts a significant but predictable impact on rainfall amount anomalies, groundwater level and spring discharge, as evidenced by second-order water isotope parameters (e.g., line conditioned-excess or line-conditioned (LC)-excess). Sea surface tempera ture anomaly (El Niño Region 3) is correlated with a reduction in mean annual and cold front rainfall across the headwaters of north-central Costa Rica. During El Niño conditions, rainfall is substantially reduced (up to 69.2%) during the critical cold fronts period, limiting groundwater recharge and promoting an early onset of minimum baseflow conditions (up to 5 months). In contrast, La Niña is associated with increased rainfall and groundwater recharge (up to 94.7% during active cold front periods). During La Niña, the long-term mean spring discharge (39 Ls-1) is exceeded 63–80% of the time, whereas, during El Niño, the exceedance time ranges between 26% and 44%. The regional hydroclimatic variability is also imprinted on the hydrogen and oxygen isotopic compositions of meteoric waters. Drier conditions favoured lower LC-excess in rainfall (-17.3‰) and spring water (-6.5‰), whereas wetter conditions resulted in greater values (rainfall = +17.5‰; spring water = +10.7‰). The lower and higher LC-excess values in rainfall corresponded to the very strong 2014–2016 El Niño and 2018 La Niña, respectively. During the recent triple-dip 2021–23 La Niña, LC-excess exhibited a significant and consistently increasing trend. These findings highlight the importance of combining hydrometric, synoptic and isotopic monitoring as ENSO sentinels to advance our current understanding of ENSO impacts on hydrological systems across the humid Tropics. Such information is critical to constraining the 21st century projections of future water stress across this fragile region.Ítem Importance of measured transpiration fluxes for modelled ecohydrological partitioning in a tropical agroforestry system(2023-12-23) Birkel Dostal, Christian; Arciniega Esparza, Saúl; Maneta, Marco P.; Boll, Jan; Stevenson, Jamie Lee; Benegas Negri, Laura Andrea; Tetzlaff, Doerthe; Soulsby, ChrisEvaporation (E) and transpiration (Tr) are the key terrestrial water fluxes to the atmosphere and are highly sensitive to land cover change. These ecohydrological fluxes can be measured directly only at small scales, such as individual plants or under laboratory experiments. Modelling is needed to upscale E and Tr estimates to plot, hillslope and catchment scales. However, model-derived ecohydrological water partitioning of E and Tr can be ambiguous, particularly when models are trained using hydrometric data and soil moisture. To test the influence of different types of data (i.e., sap flux-derived Tr, Eddy Covariance-derived actual evapotranspiration (AET) and measured soil water (SW)) on model calibration and subsequent water partitioning, we developed the low-parameter plot scale ecohydrology model EcoHydroPlot applied to a data-rich experimental agroforestry plot in humid tropical Costa Rica. The model was able to simulate SW well when calibrated with any data type, but large differences emerged in the E and Tr flux partitioning. Using only hydrometric data for calibration resulted in parameter configurations that produced greater E over Tr fluxes (Tr/AET < 0.5). The opposite was seen for model calibration using Tr data (median Tr simulations with KGE > 0.6), resulting in Tr/AET ratios close to the observed ~0.9. Further, using all measurements simultaneously (including AET, SW and Tr) did not improve simulated water partitioning. We only found small differences between sun and shade locations with slightly greater average shaded coffee transpiration at the expense of lower upper SW, higher deeper SW and less groundwater recharge compared to sun exposed coffee. This work can inform measurement priorities for applications with relatively simple conceptual ecohydrology models and emphasizes the importance of transpiration estimates for model calibration beyond tropical environments.Ítem Preface special issue: “Processes and patterns in tropical hydrology”(2023-07-04) Birkel Dostal, Christian; Duvert, Clément; Correa Barahona, Alicia Beatriz; Breña Naranjo, José AgustínThis SI aims at bringing together the state of the art in hydrological sciences of the Tropics derived from observed data, modelling, and hydrological theory, to critically outline the challenges and opportunities in tropical hydrology research. Because of greater energy inputs, larger atmospheric moisture recycling and faster rates of hydroclimatic change (including human-induced landscape and biogeochemical changes), hydrological processes and patterns in the Tropics differ from those in other hydroclimatic regions (e.g., Wohl et al., 2012). Yet, the lack of research infrastructure and funding in most tropical countries has to date precluded a more thorough understanding of hydrological processes in these highly dynamic systems. To improve hydrological predictions in this rapidly changing region, which is closely connected to and impacts the Extra Tropics (e.g., Liu et al., 2023), it is fundamental to gain new insight into the interplay between time-invariant catchment physical properties and time-variant controls on hydro logical processes.Ítem Stream respiration exceeds CO2 evasion in a low-energy, oligotrophic tropical stream(2023-03-12) Solano Rivera, Vanessa; Duvert, Clément; Birkel Dostal, Christian; Maher, Damien Troy; García, Erica A.; Hutley, Lindsay BeaumontCarbon dioxide (CO2) can be either imported to streams through groundwater and subsurface inputs of soil-respired CO2 or produced internally through stream metabolism. The contribution of each source to the CO2 evasion flux from streams is not well quantified, especially in the tropics, an underrepresented region in carbon(C) cycling studies. We used high-frequency measurements of dissolved O 2 and CO2 concentrations to estimatethe potential contribution of stream metabolism to the CO2 evasion flux in a tropical lowland headwaterstream. We found that the stream was heterotrophic all year round, with net ecosystem productivity (NEP)values ranging from 0.84 to 4.06 g C m-2 d-1 (median 1.29 g C m-2 d-1 ; here we expressed gross primary pro-ductivity (GPP) as a negative flux and ecosystem respiration (ER) as a positive flux). Positive NEP values were theresult of a relatively low and stable GPP through the seasons, compared to a higher and more variable ERfavored by the high temperatures and organic matter availability, particularly during the wet season. The CO2evasion flux was relatively low due to low turbulence (median: 1.09 g C m-2 d-1). As a result, daily NEP ratesexceeded the CO2 evasion flux with a potential contribution of 129% (median; 120–175% interquartile range), despite the strong seasonal changes in flow regime and landscape connectivity. The CO2 excess was likely trans-ported downstream, where it was ultimately emitted to the atmosphere. Our results highlight the overwhelmingimportance of ER to the C cycle of low-energy, oligotrophic tropical streams.