Browsing by Author "Timbe Castro, Edison Patricio"

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Addressing sources of uncertainty in runoff projections for a data scarce catchment in the Ecuadorian Andes
(2014) Exbrayat, Jean Francois; Buytaert, Wouter; Timbe Castro, Edison Patricio; Windhorst, David; Breuer, Lutz
Future climate projections from general circulation models (GCMs) predict an acceleration of the global hydrological cycle throughout the 21st century in response to human-induced rise in temperatures. However, projections of GCMs are too coarse in resolution to be used in local studies of climate change impacts. To cope with this problem, downscaling methods have been developed that transform climate projections into high resolution datasets to drive impact models such as rainfall-runoff models. Generally, the range of changes simulated by different GCMs is considered to be the major source of variability in the results of such studies. However, the cascade of uncertainty in runoff projections is further elongated by differences between impact models, especially where robust calibration is hampered by the scarcity of data. Here, we address the relative importance of these different sources of uncertainty in a poorly monitored headwater catchment of the Ecuadorian Andes. Therefore, we force 7 hydrological models with downscaled outputs of 8 GCMs driven by the A1B and A2 emission scenarios over the 21st century. Results indicate a likely increase in annual runoff by 2100 with a large variability between the different combinations of a climate model with a hydrological model. Differences between GCM projections introduce a gradually increasing relative uncertainty throughout the 21st century. Meanwhile, structural differences between applied hydrological models still contribute to a third of the total uncertainty in late 21st century runoff projections and differences between the two emission scenarios are marginal.
Análisis del rendimiento hídrico en cuencas de alta montaña en los Andes Ecuatorianos
(2018) Belesaca Zhunio, Katherine Daniela; Peláez Palacios, Katherine Isabel; Timbe Castro, Edison Patricio; Guallpa Guallpa, Mario Xavier
The basins of the tropical Andes comprise a variety of ecosystems, among which are Andean forests and paramo areas. The importance of these Andean ecosystems lies in the provision of environmental services. Particularly, the water supply in the Paute river basin, located in the southeastern foothills of the Ecuadorian Andes, depends on the state of conservation of the ecosystems that form its watersheds. On the other hand, the hydrological response of the mountain basins can also be controlled by physiographic factors such as soil type, vegetation cover and morphometric characteristics. In this context, the present study aims to increase the information on the role played the characteristics of the landscape on the hydrological functioning of Andean ecosystems. To reach the objective, the effects of the variability of the physical parameters and morphometric parameters in the hydric yield of the nested micro-basins of the sub-basins of the Machángara, Tomebamba and Yanuncay rivers. For the basins studied, the morphometric parameters that described most of the variability of water yield were: altitude, area, compactness coefficient, average slope of the basin, concentration time and drainage density; in this sense, the most representative water performance indicators were: runoff coefficient, maximum flow, real evapotranspiration, 65th percentile; while the indicators of water regulation were: the percentages of base flow relationship Q90/Q10, and the slope of the flow duration curve. The variability observed in the generation of runoff can also be explained due to the vegetation cover and the use of the soil
Assessment of hydrological pathways in East African montane catchments under different land use
(2018) Jacobs, Suzanne R.; Rufino, Mariana; Butterbach Bahl, Klaus; Timbe Castro, Edison Patricio; Weeser, Bjorn; Breuer, Lutz
Conversion of natural forest (NF) to other land uses could lead to significant changes in catchment hydrology, but the nature of these changes has been insufficiently investigated in tropical montane catchments, especially in Africa. To address this knowledge gap, we aimed to identify stream water (RV) sources and flow paths in three tropical montane sub-catchments (27–36 km2 ) with different land use (natural forest, NF; smallholder agriculture, SHA; and commercial tea and tree plantations, TTP) within a 1021 km2 catchment in the Mau Forest complex, Kenya. Weekly samples were collected from stream water, precipitation (PC) and mobile soil water for 75 weeks and analysed for stable isotopes of water (δ2H and δ18O) for mean transit time (MTT) estimation with two lumped parameter models (gamma model, GM; and exponential piston flow model, EPM) and for the calculation of the young water fraction. Weekly samples from stream water and potential endmembers were collected over a period of 55 weeks and analysed for Li, Na, Mg, K, Rb, Sr and Ba for endmember mixing analysis (EMMA). Solute concentrations in precipitation were lower than in stream water in all catchments (p < 0.05), whereas concentrations in springs, shallow wells and wetlands were generally more similar to stream water. The stream water isotope signal was considerably damped compared to the isotope signal in precipitation. Mean transit time analysis suggested long transit times for stream water (up to 4 years) in the three sub-catchments, but model efficiencies were very low. The young water fraction ranged from 13 % in the smallholder agriculture sub-catchment to 15 % in the tea plantation sub-catchment. Mean transit times of mobile soil water ranged from 3.2–3.3 weeks in forest soils and 4.5–7.9 weeks in pasture soils at 15 cm depth to 10.4–10.8 weeks in pasture soils at 50 cm depth. The contribution of springs and wetlands to stream discharge increased from a median of 16.5 (95 % confidence interval: 11.3–22.9), 2.1 (−3.0–24.2) and 50.2 (30.5–65.5) % during low flow to 20.7 (15.2–34.7), 53.0 (23.0–91.3) and 69.4 (43.0–123.9) % during high flow in the natural forest, smallholder agriculture and tea plantation sub-catchments, respectively. Our results indicate that groundwater is an important component of stream water, irrespective of land use. The results further suggest that the selected transit time models and tracers might not be appropriate in tropical catchments with highly damped stream water isotope signatures. A more in-depth investigation of the discharge dependence of the young water fraction and transit time estimation using other tracers, such as tritium, could therefore shed more light on potential land use effects on the hydrological behaviour of tropical montane catchments.
Do mixing models with different input requirement yield similar streamflow source contributions? Case study: a tropical montane catchment
(2021) Timbe Castro, Edison Patricio; Crespo Sánchez, Patricio Javier; Mora Abril, Enmita Lucía; Ramón Flores, Jorge David; Correa Barahona, Alicia Beatriz; Mosquera Rojas, Giovanny Mauricio
Hydrogeochemical based mixing models have been successfully used to investigate the composition and source identification of streamflow. The applicability of these models is limited due to the high costs associated with data collection and the hydrogeochemical analysis of water samples. Fortunately, a variety of mixing models exist, requiting different amount of data as input, and in data scarce regions it is likely that preference will be given to models with the lowest requirement of input data. An unanswered question is if models with high or low input requirement are equally accurate. To this end, the performance of two mixing models with different input requirement, the mixing model analysis (MMA) and the end-member mixing analysis (EMMA), were verified on a tropical montane headwater catchment (21.7 km2) in the Ecuadorian Andes. Nineteen hydrogeochemical tracers were measured on water samples collected weekly during 3 years in streamflow and eight potential water sources or end-members (precipitation, lake water, soil water from different horizons and springs). Results based on 6 conservative tracers, revealed that EMMA (using all tracers) and MMA (using pair-combinations out of the 6 conservative ones), identified the same end-members: rainfall, soil water and spring water., as well as, similar contribution fractions to streamflow from rainfall 21.9% and 21.4%, soil water 52.7% and 52.3%, and spring water 26.1% and 28.7%, respectively. Our findings show that a hydrogeochemical mixing model requiring a few tracers can provide similar outcomes than models demanding more tracers as input data. This underlines the value of a preliminary detailed hydrogeochemical characterization as basis to derive the most cost-efficient monitoring strategy.
Efectos de la variación del nivel de luz y lluvia en el microclima de parcelas experimentales cultivadas con Kikuyo (Pennisetum clandestinum) y Rye grass (Lolium multiflorum) en el cantón Guachapala de la provincia del Azuay
(2019-06-10) Aucapiña Chaca, Marco Antonio; Cajamarca Plaza, Christian Eduardo; Timbe Castro, Edison Patricio
In the province of Azuay, most pasture production systems are found as monocultures. These production systems may present vulnerability to extreme precipitation events or frost by radiation. Events that, both in recurrence and in intensity, could be increased due to phenomena such as climate change, putting at risk the sustainability of livestock activities. Before this, and to reduce the vulnerability of traditional production systems, it is necessary to adopt new production schemes such as forestpasturel systems. In this line, with the current project were analyzed the effects of different levels of light and rain, given as result two types of pasture. For this, through structures specially designed for the exclusion of light and rain, by artificial way, the microclimate of parcels 2x2m cultivated with: kikuyo (Pennisetum clandestinum) and ryegrass (Lolium multiflorum), was artificially altered. Sixty parcels were analyzed, in which 11 treatments related to different levels of light exclusion (30, 50 and 80%) and rainfall (25 and 50%) were tested, to be compared with natural parcels, in which there was no exclusion of any kind. Both in the natural parcels and in the treatments, various meteorological, physical and biological parameters as: environmental temperature, relative humidity, photosynthetically active radiation, humidity and soil temperature, and stomatal conductance were monitored. Our results show that, stomatal conductance shows significant differences in the first stage of physiological maturity, second cut for both rye grass and kikuyo with exclusion of rain T10-0, T50-25, y T90-50; the temperature and humidity of the soil showed significant values in the different treatments; the exclusion of light turned out to be a determining factor for these two variables. The temperature in the presence of light exclusion of 80% (T280-0) decreased to 5 ° C in comparison to normal environmental conditions (T10-0), with a significance value of 0.048; the soil humidity varied from 0.32 m3_m-3 in 80% (T280-0) of light exclusion in comparison to 0.28 m3_m-3 under normal conditions (T10-0), with a value of significance 2e-16; this is because the presence of shade prevents an accelerated loss of water stored in the parcel; the environmental temperature and relative humidity did not show significant differences between the treatments
Evaluation of 1D hydraulic models for the simulation of mountain fluvial floods: a case study of the Santa Bárbara river in Ecuador
(2019) Pinos Flores, Juan Andres; Timbe Castro, Edison Patricio; Timbe Castro, Luis Manuel
River flooding is a key topic for water managers because of social and economic losses it can cause. The complex topography and dynamics of mountain rivers has limited the analysis of their behavior during flood events (e.g., sediment transport, flooding). This study aims to test the performance of three hydraulic 1D models (HEC-RAS, MIKE 11, and Flood Modeller) to estimate inundation water levels for a mountain river. The evaluation of these models was performed considering steady state conditions through 10 scenarios, i.e. five discharge return periods, and two types of cross sections data (a) type I, a detailed field survey complemented with information extracted from DEM, derived from LiDAR; and (b) type II, cross sections exclusively derived from the DEM. The research was conducted for a reach of 5 km of the Santa Bárbara River, with an average slope of 0.25%. HHEC-RAS model results for cross sections type I, were previously validated and therefore used as reference for comparison between other models and scenarios. The goodness-of-fit between models was measured based on the Nash-Sutcliffe model efficiency coefficient (EF). The main goal of the current study was to determine the variability of inundation level results compared with a validated model as reference, using the same input data for the three modeling packages. Our analysis shows that, when using cross section type I, the evaluated modeling packages yield similar results (EF were between 0.94 and 0.99). On the other hand, the goodness of fit decreased when using type II data, with an average EF of 0.98 (HEC-RAS), 0.88 (Flood Modeller) and 0.85 (MIKE 11) when compared to the reference model. The authors conclude that it is highly recommend for practitioners to use geometric data type I instead of type II in order to obtain similar performance in the tested models. Only HEC-RAS type II has the same performance as type I models (average EF of 0.98).
Global climate change impacts on local climate and hydrology
(Springer, Berlin, Heidelberg, 2013) Timbe Castro, Edison Patricio
Global climate change will most likely have a severe impact on local climate and hydrological cycling in the tropical montane rainforest. We used a simple statistical downscaling technique for eight general circulation models and two IPCC AR4 emission scenarios (A1B, A2) to forecast feasible local climate conditions for the San Francisco river basin for three future time slices (2010–2039, 2040–2069, 2070–2099). These simulations were then used as forcing data for an ensemble of seven catchment scale rainfall-runoff models to investigate the effects on local hydrological fluxes. Precipitation for both emission scenarios is expected to increase, especially in the months May and June. These increases in precipitation input will lead to even more dynamic discharges as today. However, part of the increasing water input is compensated by raising evapotranspiration due to higher temperatures. Finally, we give an outlook on feasible future trends of water-related ecosystem services under climate change.
Identificación de fuentes de generación de escorrentía en los Andes tropicales: estudio de múltiples modelos basados en trazadores
(2018-10-04) Ramón Flores, Jorge David; Timbe Castro, Edison Patricio
Mixing models have been applied to hydrogeochemical datasets to investigate runoff sourcing in experimental catchments. However, long-term application of these methodologies remains limited given the high costs related to the collection and hydrogeochemical analyses of water samples. In this study we applied two mixing models of different complexity to identify the runoff contributing sources (end-members) of a headwater catchment (21.7 km2) in the Ecuadorian Andes. We used a robust dataset of 19 hydrogeochemical tracers measured in weekly water samples from streamflow and eight potential end-members (precipitation, lake water, soil water, and spring water) for one-year. We applied a mixing model analysis (MMA) and an end-member mixing analysis (EMMA) to the geochemical dataset to identify the contributions from different end-members to runoff and compared the water fractions determined by both methods. Results show that both methods, MMA and EMMA, yield comparable fractions of rainfall (21.9% and 21.4%), soil water (52.7% and 52.3%), and spring water (21.1% and 28.7%) to streamflow. Results also indicate that MMA using 6 conservative tracers allows for a clear identification of the three end-members and similar proportions of water contribution to runoff than EMMA. Our findings depict the value of conducting detailed hydrogeochemical characterizations to define efficient (low cost) sampling strategies that provide valuable hydrological information that can be used by water managers. Moreover, the delineation of such strategies can help to maintain the collection of hydrogeochemical data at finer temporal resolutions for longer time periods in order to identify long-term changes in catchment hydrological behavior.
Impact of elevation and weather patterns on the isotopic composition of precipitation in a tropical montane rainforest
(2013) Windhorst, David; Waltz, T.; Timbe Castro, Edison Patricio; Frede, H. G.; Breuer, Lutz
This study presents the spatial and temporal variability of δ18O and δ2H isotope signatures in precipitation of a south Ecuadorian montane cloud forest catchment (San Francisco catchment). From 2 September to 25 December 2010, event sampling of open rainfall was conducted along an altitudinal transect (1800 to 2800 m a.s.l.) to investigate possible effects of altitude and weather conditions on the isotope signature. The spatial variability is mainly affected by the altitude effect. The event based δ18O altitude effect for the study area averages −0.22‰ × 100 m−1 (δ2H: −1.12‰ × 100 m−1). The temporal variability is mostly controlled by prevailing air masses. Precipitation during the times of prevailing southeasterly trade winds is significantly enriched in heavy isotopes compared to precipitation during other weather conditions. In the study area, weather during austral winter is commonly controlled by southeasterly trade winds. Since the Amazon Basin contributes large amounts of recycled moisture to these air masses, trade wind-related precipitation is enriched in heavy isotopes. We used deuterium excess to further evaluate the contribution of recycled moisture to precipitation. Analogously to the δ18O and δ2H values, deuterium excess is significantly higher in trade wind-related precipitation. Consequently, it is assumed that evaporated moisture is responsible for high concentrations of heavy isotopes during austral winter.
Mapeo del peligro de inundación en ríos de montaña, caso de estudio del río Burgay
(2012) Timbe Castro, Luis Manuel; Timbe Castro, Edison Patricio
HEC-RAS, an one-dimensional hydraulic model, was used to simulate and map floods along a 10 km stretch of the Burgay river. Analysis of the results reveals that the model is capable of simulating the flood and inundation situation along rivers in the Andean region, notwithstanding scarcity of information. Local governments (e.g. municipalities) can use the flood hazard zoning maps for the sustainable management of alluvial plains, through the planning and implementation of structural or non-structural measures (e.g. land use planning) considering the physical conditions of the riverbanks.
Model intercomparison to explore catchment functioning: results from a remote montane tropical rainforest
(2012) Plesca, Ina; Timbe Castro, Edison Patricio; Exbrayat, Jean Francois; Windhorst, David; Kraft, Philipp; Crespo Sánchez, Patricio Javier; Vaché, K. B.; Frede, Hans Georg; Breuer, Lutz
Catchment-scale runoff generation involves a complex interaction of physical and chemical processes operating over a wide distribution of spatial and temporal scales. Understanding runoff generation is challenged by this inherent complexity – the more uncertain step of predicting the hydrologic response of catchments is that much more challenging. Many different hypotheses have been implemented in hydrological models to capture runoff generation processes and provide hydrologic predictions. These concepts have been developed based on extended field observations. Here we propose inferring water flux understanding and catchment exploring through the application of a variety of available hydrological models as a mechanism to build upon and extend models that have been developed to capture particular hydrological processes. We view this ensemble modeling strategy as particularly appropriate in ungauged catchments. The study is carried out in a tropical montane rainforest catchment in Southern Ecuador. The catchment is 75 km2 and is covered by forest in the south, while the northern slopes have been partly deforested for grazing. Annual rainfall is highly variable, reaching up to 5700 mm per year in the upper parts of the catchment. To explore the dominating runoff processes, an ensemble of 6 hydrological models with different structures applied over different levels of both spatial and temporal detail was developed. The ensemble includes spatially lumped (HBV-light), semi-distributed (HEC-HMS, CHIMP, SWAT, LASCAM) and a fully distributed model (HBV-N-D). The hydro-statistical toolkit WETSPRO was used to characterize simulated and observed hydrographs. Estimated baseflow indices, flow minima and maxima, flow duration curves and cumulative errors were generated and compared among the ensemble of models. This process facilitated the exploration of processes controlling runoff generation, enabled an evaluation of the applicability of the screened models to tropical montane rainforests, and provided the capacity to evaluate and explain where different models failed.
Modelización del balance hídrico del suelo en Pendientes fuertes
(1999) Ochoa Yumbla, Juan Pablo; Timbe Castro, Edison Patricio; De Bièvre, Bert
Multicriteria assessment of water dynamics reveals subcatchment variability in a seemingly homogeneous tropical cloud forest catchment
(2017) Timbe Castro, Edison Patricio; Feyen, Jan; Timbe Castro, Luis Manuel; Crespo Sánchez, Patricio Javier; Célleri Alvear, Rolando Enrique; Windhorst, David; Frede, Hans Georg; Breuer, Lutz
To improve the current knowledge of the rainfall–runoff phenomena of tropical montane catchments, we explored the usefulness of several hydrological indicators on a nested cloud forest catchment (76.9 km2). The used metrics belong to 5 categories: baseflow mean transit time, physicochemical properties of stream water, land cover, topographic, and hydrometric parameters. We applied diverse statistical techniques for data analysis and to contrast findings. Multiple regression analysis showed that mean transit times of base flow could be efficiently predicted by sodium concentrations (higher during baseflows) and temperatures of stream water, indicating a major influence of geomorphology rather than topographic or land cover characteristics. Principal component analysis revealed that no specific subset of catchment indicators could be identified as prevailing descriptors for all catchments. The agglomerative hierarchical clustering analysis provided concomitant results, implying larger levels of dissimilarity between smaller subcatchments than between larger ones. Overall, results point out an intricate interdependence of diverse processes at surface and subsurface level indicating a high level of heterogeneity. Disregarding heterogeneity of nested or paired catchments could lead to incomplete or misleading conclusions, especially in tropical mountain regions where pronounced spatial and temporal gradients are present.
Sampling frequency trade-offs in the assessment of mean transit times of tropical montane catchment waters under semi-steady-state conditions
(2015) Timbe Castro, Edison Patricio; Windhorst, David; Célleri Alvear, Rolando Enrique; Timbe Castro, Luis Manuel; Crespo Sánchez, Patricio Javier; Frede, Hans Georg; Feyen, Jan; Breuer, Lutz
Precipitation event samples and weekly based water samples from streams and soils were collected in a tropical montane cloud forest catchment for 2 years and analyzed for stable water isotopes in order to understand the effect of sampling frequency in the performance of three lumped-parameter distribution functions (exponential-piston flow, linear-piston flow and gamma) which were used to estimate mean transit times of waters. Precipitation data, used as input function for the models, were aggregated to daily, weekly, bi-weekly, monthly and bi-monthly sampling resolutions, while analyzed frequencies for outflows went from weekly to bi-monthly. By using different scenarios involving diverse sampling frequencies, this study reveals that the effect of lowering the sampling frequency depends on the water type. For soil waters, with transit times on the order of few weeks, there was a clear trend of over predictions. In contrast, the trend for stream waters, which have a more damped isotopic signal and mean transit times on the order of 2 to 4 years, was less clear and showed a dependence on the type of model used. The trade-off to coarse data resolutions could potentially lead to misleading conclusions on how water actually moves through the catchment, notwithstanding that these predictions could reach better fitting efficiencies, fewer uncertainties, errors and biases. For both water types an optimal sampling frequency seems to be 1 or at most 2 weeks. The results of our analyses provide information for the planning of future fieldwork in similar Andean or other catchments.
Stable water isotope tracing through hydrological models for disentangling runoff generation processes at the hillslope scale
(2014) Windhorst, David; Timbe Castro, Edison Patricio; Kraft, Philipp; Frede, Hans Georg; Breuer, Lutz
Hillslopes are the dominant landscape components where incoming precipitation becomes groundwater, streamflow or atmospheric water vapor. However, directly observing flux partitioning in the soil is almost impossible. Hydrological hillslope models are therefore being used to investigate the processes involved. Here we report on a modeling experiment using the Catchment Modeling Framework (CMF) where measured stable water isotopes in vertical soil profiles along a tropical mountainous grassland hillslope transect are traced through the model to resolve potential mixing processes. CMF simulates advective transport of stable water isotopes 18O and 2H based on the Richards equation within a fully distributed 2-D representation of the hillslope. The model successfully replicates the observed temporal pattern of soil water isotope profiles (R2 0.84 and Nash–Sutcliffe efficiency (NSE) 0.42). Predicted flows are in good agreement with previous studies. We highlight the importance of groundwater recharge and shallow lateral subsurface flow, accounting for 50 and 16% of the total flow leaving the system, respectively. Surface runoff is negligible despite the steep slopes in the Ecuadorian study region.
Understanding uncertainties when inferring mean transit times of water trough tracer-based lumped-parameter models in Andean tropical montane cloud forest catchments
(2014) Timbe Castro, Edison Patricio; Crespo Sánchez, Patricio Javier; Feyen, Jan; Windhorst, David; Frede, Ha G.; Breuer, Lars
Weekly samples from surface waters, springs, soil water and rainfall were collected in a 76.9 km2 mountain rain forest catchment and its tributaries in southern Ecuador. Time series of the stable water isotopes δ18O and δ2H were used to calculate mean transit times (MTTs) and the transit time distribution functions (TTDs) solving the convolution method for seven lumped-parameter models. For each model setup, the generalized likelihood uncertainty estimation (GLUE) methodology was applied to find the best predictions, behavioral solutions and parameter identifiability. For the study basin, TTDs based on model types such as the linear–piston flow for soil waters and the exponential–piston flow for surface waters and springs performed better than more versatile equations such as the gamma and the two parallel linear reservoirs. Notwithstanding both approaches yielded a better goodness of fit for most sites, but with considerable larger uncertainty shown by GLUE. Among the tested models, corresponding results were obtained for soil waters with short MTTs (ranging from 2 to 9 weeks). For waters with longer MTTs differences were found, suggesting that for those cases the MTT should be based at least on an intercomparison of several models. Under dominant baseflow conditions long MTTs for stream water ≥ 2 yr were detected, a phenomenon also observed for shallow springs. Short MTTs for water in the top soil layer indicate a rapid exchange of surface waters with deeper soil horizons. Differences in travel times between soils suggest that there is evidence of a land use effect on flow generation.