TY - JOUR
T1 - Spatially distributed tracer-aided modelling to explore water and isotope transport, storage and mixing in a pristine, humid tropical catchment
AU - Dehaspe, Joni
AU - Birkel, Christian
AU - Tetzlaff, Doerthe
AU - Sánchez-Murillo, Ricardo
AU - Durán-Quesada, Ana María
AU - Soulsby, Chris
N1 - This project was initiated with a BGS fellowship to Josie Geris (University of Aberdeen) and C. B. and an Ideawild grant to C. B. Support by Tito Maldonado with the cluster computing facility at CIGEFI, UCR, is greatly acknowledged. Furthermore, we thank Vanessa Solano and Sebastian Granados for processing the multispectral imagery. Many helping hands in the field are acknowledged. The UCR‐funded “Isotopes in tropical ecosystems network IsoNET” and the project 217‐B4‐39 is greatly acknowledged. We also thank the VEWA project that enabled early work on the STARR model. We thank one anonymous reviewer and Matthias Beyer for their constructive comments that helped improve the paper.
PY - 2018/10/15
Y1 - 2018/10/15
N2 - 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.
AB - 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.
KW - Costa Rica
KW - humid tropics
KW - ReBAMB
KW - stable isotopes
KW - tracer-aided modelling
KW - tracers
UR - http://www.scopus.com/inward/record.url?scp=85053271675&partnerID=8YFLogxK
U2 - 10.1002/hyp.13258
DO - 10.1002/hyp.13258
M3 - Article
AN - SCOPUS:85053271675
VL - 32
SP - 3206
EP - 3224
JO - Hydrological Processes
JF - Hydrological Processes
SN - 0885-6087
IS - 21
ER -