Spatially distributed tracer‐aided modelling to explore water and isotope transport, storage and mixing in a pristine, humid tropical catchment
Spatially distributed tracer‐aided modelling to explore water and isotope transport, storage and mixing in a pristine, humid tropical catchment
复制标题
空间分布示踪剂辅助建模，探索原始潮湿热带流域中的水和同位素传输、储存和混合
作者：
J. Dehaspe;C. Birkel;D. Tetzlaff;R. Sánchez‐Murillo;A. Durán‐Quesada;C. Soulsby
潮湿热带地区快速变化的水源流域为饮用水、灌溉、水力发电和生态系统连通性提供了重要资源。然而，下游使用的此类资源仍未得到研究。为了更好地了解原始雨林对水和示踪剂通量的行为和影响，我们使用哥斯达黎加 3.2 平方公里圣洛伦西托流域的基于事件的稳定同位素数据，采用了相对简约的空间分布示踪剂辅助降雨径流 (STARR) 模型。 STARR 用于模拟雨林对水和稳定同位素的拦截，结果表明，与总降雨量相比，径流中的同位素显着富集。在高空间（10 m）和时间（每小时）分辨率下对排放（Kling-Gupta 效率 [KGE] ~0.8）和溪流水中的稳定同位素（KGE ~0.6）进行可接受的并发模拟，表明系统是一个快速响应的系统。约 90% 的年平均径流（2,099 毫米）由快速的近地表径流成分组成，而只有约 10% 来自较深层的地下水。由于相对湿度较高（平均 96%）和云层限制辐射输入，截取和土壤储存模拟的实际蒸散量 (ET) 较低（约 420 毫米/年）。模型显示，在这个陡峭、断裂的火山集水区，地下水储量变化很大（约 10 至 500 毫米），可维持旱季基流。这些地下水集中在河岸地区，作为与河流相连的冲积-崩积含水层。这得到了降雨径流同位素模拟的支持，显示了对降雨的“快速”河流响应，仅具有中等阻尼效应，并且在基流期间来自较深层地下水（约 400 毫米额外混合体积）的恒定同位素特征。这项工作是将空间分布的示踪剂辅助模型应用于热带雨林环境的首次尝试，探索陡峭、断裂的火山流域的水文功能。我们还强调了热带源头流域的局限性，并提出了未来数据收集和空间分布示踪剂辅助模型开发的路线图。
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.