Quantitative estimations of ecohydrological water partitioning into evaporation and transpiration remains mostly based on plot‐scale investigations that use well‐instrumented, 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 streamwater isotope record of 46 streams. The overall model performance for the best discharge 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 topographical gradient. Climatic drivers overrode smaller, landcover‐dependent transpiration 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 approximation of spatio‐temporal dynamics of how water is partitioned, stored and transported beyond the experimental catchment scale of only a few km2.
Abstract. Catchment-scale hydrological studies on drylands are lacking because of thescarcity of consistent data: observations are often available at the plotscale, but their relevance for the catchment scale remains unclear. Adatabase of 24 years of stream gauge discharge and homogeneoushigh-resolution radar data over the eastern Mediterranean allows us to describe the properties of floods over catchments spanning from desert toMediterranean climates, and we note that the data set is mostly of moderateintensity floods. Comparing two climatic regions, desert and Mediterranean,we can better identify specific rainfall-runoff properties. Despite the large differences in rainfall forcing between the two regions, the resulting unitpeak discharges and runoff coefficients are comparable. Rain depth andantecedent conditions are the most important properties to shape floodresponse in Mediterranean areas. In deserts, instead, storm core propertiesdisplay a strong correlation with unit peak discharge and, to a lesser extent,with runoff coefficient. In this region, an inverse correlation with meancatchment annual precipitation suggests also a strong influence of localsurface properties. Preliminary analyses suggest that floods in catchmentswith wet headwater and dry lower section are more similar to desertcatchments, with a strong influence of storm core properties on runoffgeneration.
more » « less- Award ID(s):
- 1632048
- NSF-PAR ID:
- 10113327
- Date Published:
- Journal Name:
- Hydrology and Earth System Sciences
- Volume:
- 23
- Issue:
- 6
- ISSN:
- 1607-7938
- Page Range / eLocation ID:
- 2665 to 2678
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.5194/hess-23-2665-2019
