## 3 Result
### Setting the South American and Tibetan Lakes and Basins in a Global Context  
As a final consideration, we placed the lakes' and hydrologic basins' mass variations into a global context, which was possible by merging the different databases of the lakes/basins' outlines with the time series of the lake level/moisture variations. The procedure entails calculating the time series of the mass variation for each water body/basin and then extracting the seasonal amplitude through the best fit of Equation (1). The Gigaton seasonal variation vs. the basin area is plotted in Figure 16, distinguishing between the basins of Africa, South America, and Asia. The analysis has considered basins with areas \(>5\,10^{5}\) km\({}^{2}\). Given the previous analysis, we have an estimate of the detectability limit of GRACE and MOCAST+ for basins of the size of the Orinoco and Parana (Figure 11); these thresholds are shown as horizontal lines for the basin areas of \(9\,10^{5}\) km\({}^{2}\) and \(2.5\,10^{6}\) km\({}^{2}\). In order to be monitored by satellite gravimetry, a basin should be above the detectability threshold. In South America, we did not find basins with areal extensions similar to the Orinoco (about \(10^{6}\) km\({}^{2}\)) with seasonal mass variations at the detectability limit (8-10 Gt). However, in other climatic contexts, as in South Africa and Asia, there appear to be some possible basins fitting these criteria. Monitoring such basins would definitely benefit from a high-sensitivity mission such as MOCAST+. Similar to what we performed previously for the GLDAS seasonal component, we verified which other potential lakes/reservoirs worldwide could benefit from a MOCAST+ monitoring. We considered seasonal mass variations occurring in the lakes/reservoirs of the DAHITI database [24] for Asia and Africa. For each lake/reservoir time-series of the DAHITI database we extracted the annual seasonal lake level amplitude and multiplied it by the area of the basin, obtained from the watershed database [23]. This way we could easily obtain the seasonal mass variation. Figure 15: Comparison between the retrieved anomaly patterns for the Paranał long-period hydrologic masses and the long-period variation in Tibetan lakes. Left—full resolution signal; center—signal synthetized up to d/o 32, corresponding to what would be seen after 5 years by GRACE; right—signal synthetized up to d/o 49, corresponding to what would be seen after 5 years by MOCAST+. Fields calculated at 250 km altitude. Figure 16 reports the seasonal mass variation for the considered lakes as a function of the area for lakes/reservoirs in Africa (blue), Asia (red), and South America (black). There is clearly a scaling law that causes the large trend in the scatter plot; however, inside a small interval of areas, we also observe a remarkable variability in terms of the seasonal mass component. According to our simulations and detectability criteria, the Sobradinho reservoir acts as a lower bound for a clear detection of the seasonal signals of lakes/reservoirs. Therefore, lakes and reservoirs with similar seasonal amplitudes and equal or larger areas would  
Figure 16: Scatterplot of seasonal hydrologic mass amplitudes for lakes and basins versus area; (**a**) Relation between amplitude of the seasonal mass variation and area of the hydrologic basin. Amazon, Paraná, and Orinoco basins have been labelled. Red and blue lines report the lowest basin detectable by GRACE and MOCAST+: these basins have areal extents similar to the Orinoco but experience lower seasonal mass variations. For GRACE, the detectability level is 25 Gt while for MOCAST+ it is 8 Gt. (**b**) Lakes/reservoirs’ seasonal mass amplitudes as function of area. Different colors for different geographical regions; triangles are artificial reservoirs. Dashed lines (near Sobradinho) bound the detectability area according to our criteria employing a MOCAST+ mission. certainly benefit from a MOCAST+ mission. This area of interest is bounded in the graph by two vertical and horizontal dashed lines.