Quantified medium- and long-term hydrological datasets are scarce in South Africa, yet they are essential to gain understanding of natural systems, contribute to ecosystem conservation, and ultimately quantify water balance processes accurately. A hydrological experiment was carried out at Riverlands Nature Reserve (Western Cape, South Africa) in order to quantify the components of the soil water balance at experimental sites occupied by endemic and invasive vegetation. In two separate follow-up projects, five-year time series were collected in three treatments, namely, endemic fynbos vegetation, bare soil, and land invaded by Acacia saligna. Rainfall was recorded daily with a manual rain gauge. Groundwater levels were logged hourly at 14 boreholes. Volumetric soil water contents and soil temperatures were logged hourly at different depths in the soil profile. Groundwater levels and soil water contents responded to rainfall with very clear seasonal trends. The data can be applied in water balance and evapotranspiration studies, unsaturated flux studies, soil temperature profile studies, and rainfall-groundwater level response analysis and for calibrating and validating a wide range of hydrological models. 1. Introduction The quantification of water resources and the water cycle are of utmost importance in water resources planning and management. Previous studies have indicated that water resources use and availability are dynamic depending on climate, population, land use, economic growth, technological change, and other socioeconomic factors [1]. It is therefore essential to monitor the components of the water balance in order to describe these dynamic trends. The importance of long-term monitoring in natural sciences is also acknowledged as this helps in understanding complex ecological systems and evaluating disturbances due to changes in land use, management, and climate [2]. Long-term monitoring also contributes to national and international networks for the large-scale assessment of water resources [3]. This is particularly important when historic data are scarce, especially in arid regions that experience water stress, where knowledge of the water use of vegetation could have enormous implications to water resources management. Ultimately, monitored data are used in a variety of methods and models for water resources assessment, planning, and management interventions [4]. Alien invasive plants are species introduced in an area due to intentional or accidental human activity and have the potential to spread over a considerable area [5]. In recent
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