LCZO -- Stable Isotopes -- Stable Isotope (δ18O and δ2H) Data -- Puerto Rico -- (1994-2013)

Like many mountainous areas in the tropics, watersheds in the Luquillo Mountains of eastern Puerto Rico have abundant rainfall and stream discharge and provide much of the water supply for the densely populated metropolitan areas nearby. Projected changes in regional temperature and atmospheric dynamics as a result of global warming suggest that water availability will be affected by changes in rainfall patterns. It is essential to understand the relative importance of different weather systems to water supply to determine how changes in rainfall patterns, interacting with geology and vegetation, will affect the water balance. To help determine the links between climate and water availability, stable isotope signatures of precipitation from different weather systems were established to identify those that are most important in maintaining streamflow and groundwater recharge. Precipitation stable isotope values in the Luquillo Mountains had a large range, from fog/cloud water with δ2H, δ18O values as high as +12 ‰, −0.73 ‰ to tropical storm rain with values as low as −127 ‰, −16.8 ‰. Temporal isotope values exhibit a reverse seasonality from those observed in higher latitude continental watersheds, with higher isotopic values in the winter and lower values in the summer. Despite the higher volume of convective and low-pressure system rainfall, stable isotope analyses indicated that under the current rainfall regime, frequent trade -wind orographic showers contribute much of the groundwater recharge and stream base flow. Analysis of rain events using 20 years of 15 -minute resolution data at a mountain station (643 m) showed an increasing trend in rainfall amount, in agreement with increased precipitable water in the atmosphere, but differing from climate model projections of drying in the region. The mean intensity of rain events also showed an increasing trend. The determination of recharge sources from stable isotope tracers indicates that water supply will be affected if regional atmospheric dynamics change trade- wind orographic rainfall patterns in the Caribbean.

For more data a USGS open file report is available: Stable Isotope (δ18O and δ2H) Data for Precipitation, Stream Water, and Groundwater in Puerto Rico http://dx.doi.org/10.3133/ofr20141101

热带地区众多山地地带相似，波多黎各东部洛奎洛山脉的流域区域降雨充沛，溪流流量丰富，为周边人口密集的大都市地区提供了大部分水源。由于全球变暖导致的区域温度和大气动力学变化预测，水资源的可用性将受到降雨模式变化的影响。了解不同天气系统对水源相对重要性是至关重要的，以便确定降雨模式的变化，与地质和植被的相互作用将如何影响水资源平衡。为了帮助确定气候与水资源可用性之间的联系，不同天气系统的降水稳定同位素特征被建立，以识别那些在维持溪流流量和地下水补给中最为重要的因素。洛奎洛山脉的降水稳定同位素值范围广泛，从雾/云水中的δ2H、δ18O值高达+12 ‰、−0.73 ‰，至热带风暴雨中的值低至−127 ‰、−16.8 ‰。时间同位素值显示出与高纬度大陆流域所观察到的季节性相反，冬季同位素值较高，夏季值较低。尽管对流和低压系统降雨的体积较大，但稳定同位素分析表明，在当前的降雨条件下，频繁的信风地形降雨对地下水补给和溪流基流贡献颇多。使用位于山顶（海拔643米）20年15分钟分辨率的降雨事件分析显示，降雨量呈增加趋势，与大气中可降水量的增加一致，但与该区域气候模型预测的干燥趋势不同。降雨事件的平均强度也显示出增加趋势。利用稳定同位素示踪剂确定补给源表明，如果区域大气动力学改变加勒比地区的信风地形降雨模式，将影响水资源供应。有关更多数据，可查阅美国地质调查局（USGS）公开文件报告：波多黎各降水、溪流水和地下水的稳定同位素（δ18O和δ2H）数据，链接：http://dx.doi.org/10.3133/ofr20141101。