## 4 Results and Discussion
### Isotopic Composition  
The summarised data for \(\delta^{2}\)H and \(\delta^{18}\)O values for the investigated geothermal spring water and boreholes are presented in Table 2. \(\delta^{2}\)H and \(\delta^{18}\)O values were plotted for groundwater samples, which gave us a clear understanding of the origin and recharge processes (Figure 9). It was observed that the groundwaters (geothermal springs at Tshipise, Sagole, and Mphephu) were more depleted in the winter compared to the summer season. This could be attributed to paleoclimatic effects, which make the groundwater isotopically depleted with respect to modern waters. The paleoclimatic effect is manifested by the depletion of stable isotopes with respect to modern waters [47] and is shifted along the TMWL towards negative values (Figure 9). That is to say, there is a possible evaporation of rainwater before infiltration mixing with groundwater, which would result in the slight enrichment in the summer. As mentioned earlier, most of the rainfall within Soutpansberg occurred during the summer season, but the groundwaters were more depleted in the winter than the summer season (\(\delta^{18}\)O or \(\delta^{2}\)H values were lesser). Hence, no amount effect was observed, but a high temperature effect was observed that led to evaporation, resulting in seasonal effects, which were profound in the study and supported by other studies [47; 48; 49]. The isotopic signatures of the groundwaters were depleted isotopically in the winter compared to the summer, which negated the amount effects; that is, the lesser the volume of rainfall, the higher the \(\delta^{18}\)O or \(\delta^{2}\)H content [50; 51]. Figure 9 on isotopic data differentiates between the three possible types of origin of geothermal water, i.e., magnetic, oceanic, and meteoric. Ranges of \(\delta^{18}\)O and \(\delta\)D of all the geothermal water samples are \(-5.7\) to \(-4.8\%\)\(\infty\) and \(-33.5\) to \(-24.6\%\)\(\infty\), respectively (Table 2). These data showed no presence of any significant amount of magnetic water, which generally has \(\delta^{18}\)O: \(+6\) to \(+9\%\)\(\infty\) and \(\delta\)D: \(-40\) to \(-80\%\)\(\infty\) ([PERSON] and [PERSON], 1980; [PERSON], 1992). The possibility of oceanic origin of these waters was ruled out because \(\delta^{18}\)O and \(\delta\)D were not approximately \(0\%\)\(\infty\) ([PERSON], 1961). The isotopic compositions of groundwater (\(\delta^{2}\)H = \(-24.6\) to \(-33.5\%\)\(\infty\) and \(\delta^{18}\)O = \(-4.82\) to \(-5.82\%\)\(\infty\)) were significantly lighter than those of modern rainwater (\(\delta^{2}\)H = \(-9.8\%\)\(\infty\) and \(\delta^{18}\)O = \(-2.7\%\)\(\infty\)) [35], indicating that such groundwater could possibly originate from seepage  
Figure 8: Relation between Na\({}^{+}\) and Cl\({}^{-}\) in the geothermal springs within Soutpansberg. of meteoric water in the past during colder climates ([PERSON] and [PERSON], 2018). Hence, the origin of these waters is possibly meteoric. The isotopic ranges of the geothermal springs/groundwater were relatively reflective of rainwater signature (\(\delta\)D = \(-9.8\%\)\(\infty\) and \(\delta^{18}\)O = \(-2.7\%\)\(\infty\)). This indicated that the groundwater came from precipitation that took place in the high mountain of the Soutpansberg mountain range. Most groundwater samples might have derived from the infiltration of local precipitation with a significant contribution of another type of water in the deeper part of the aquifer. The plotted \(\delta^{2}\)H against \(\delta^{18}\)O diagram shows the geothermal springs and thermal boreholes plot above/below and close to the local meteoric water line (LMWL) (Figure 9) indicative of meteoric origin, which implied that modern rainfall was the fundamental component of these groundwaters. Groundwater samples such as TSW, TSS, and SGS fell below the LMWL, which implied they were subjected to evaporation before or during their underground transit ([PERSON] and [PERSON], 2018).