The stable isotopes of water (¹⁸O, ²H) and other hydrochemical properties were used to assess seasonal changes between sources of stream water and flow pathways in baseflow conditions for two headwater sub-catchments (∼3 km²) of the Jonkershoek, a mountainous catchment in the Western Cape of South Africa. The sub-catchments differ in land cover, one is dominated by indigenous fynbos vegetation and the other by pine plantation. Stream water, higher elevation springs, and lower elevation groundwater samples were collected monthly from January 2018 to January 2019, and were analysed for stable isotopes, electrical conductivity (EC) and pH. The stream water isotopic values resembled those of groundwater during the dry and wet seasons. Results indicated a steady contribution of spring discharge to streams during the dry season, with rainfall contribution less evident. Wet season flows were attributed to interflow including perennial and ephemeral springs. Spatial variations in EC between the sub-catchments were indicative of a greater proportional input from subsurface water, more evaporation and/or more mineral dissolution in the pine-dominated sub-catchment. The spatiotemporal variability in EC was significantly larger than for the stable isotopes. These findings enabled conceptualization of streamflow generation processes that can support strategic water resource management practices in this region.

水的稳定同位素（¹⁸ O，² H）和其他水化学性质用于评估两个上游水源汇水区（〜3 km ^2）的基流条件下溪流水源与流路之间的季节性变化），位于南非西开普省的山区集水区Jonkershoek。这些子汇水区的土地覆盖率有所不同，其中一个主要是当地的蕨类植物植被，另一个是松树人工林。从2018年1月至2019年1月每月采集溪流水，高海拔泉水和低海拔地下水样品，并分析其稳定同位素，电导率（EC）和pH值。在干燥和潮湿季节，溪流水的同位素值类似于地下水的同位素值。结果表明，在干旱季节，春季排泄物对溪流的贡献稳定，而降雨贡献则不那么明显。湿季流量归因于包括常年性和短暂性泉水在内的相互影响。子汇水区之间EC的空间变化表明，在松树为主的子汇水区中，地下水的比例输入更大，蒸发量更大和/或矿物质溶解度更高。EC的时空变异性明显大于稳定同位素的时空变异性。这些发现使得能够概念化水流产生过程，可以支持该地区的战略性水资源管理实践。