## 4 Paleolakes and Groundwater
### Hypothetical Paleolake between Kharga and Toshka
Based on the presence of lake sediments in the northernmost part of the oasis and the elevations of Early and Middle Holocene sites, lake levels at 170 m asl have been proposed for this Holocene lake [56], similar to the level seen in our results in the southern part of the area of interest. A large lake in this oasis was hypothesized already by [57], but there has been disagreement as to the age of such a lake--it was considered as rather a Pleistocene than Holocene feature by [58]. An earlier and still larger lake, extending further south, is allowed for (but not tested) in this area by [PERSON] et al. [56] as well. The existence of an earlier and larger lake in the southern part of the Egyptian Western Desert is difficult to assess using the evidence from the Toshka-Kiseiba depression alone. The depression in its current shape is the result of repeated erosion, deflation and deposition in the past, particularly during the hyper-arid phase between ~70,000 BP and ~11,500 BP that removed most of the earlier sediments and had also scooped out the deflational basins in the depression that were refilled as seasonal lakes during the Holocene [26]. The Pleistocene evidence is thus only rarely found in situ. It occurs more frequently as eoilsed Acheulean (Lower Paleolithic, ~500,000-300,000 BP) or Mousterian and Aterian (Middle Paleolithic, ~175,000-70,000 BP) lithic pieces, scattered on deflational surfaces, dropped there from much higher elevations [27; 28], or as pieces reused in much later Holocene contexts [29; 59]. An exception is the only Lower Paleolithic cluster of sites in our corpus (no. 3 in Table 1) situated on a 5-km-wide plateau that constitutes the remnants of an Acheulian surface preserved ca. 20 m above the surrounding Holocene terrain [28]. Its correlation with the 200-meter contour (Figure 18e) is of interest but insufficient alone to support the existence of a large lake in this area. Further evidence in this respect was presented by [PERSON] [60] and [PERSON] et al. [52], who proposed a lake at ~190 m asl that would have filled both the northern and southern parts of our area of interest. Another, even larger lake was hypothesized by [52] at ~247 m asl based on the evidence of Middle Paleolithic occupations at Selima to the south and Bir Tarfawi and Bir Sahara to the west of our research area. In the latter two basins, a sequence of five lakes dated between ~175,000 and 70,000 BP was established. Some of them were comparatively deep and, in combination with precipitation of ca. 500 mm per year, capable of supporting large animals and fish that were found in substantial amounts in the vicinity of these lake sites, including species found today only in the Nile, Chad or Niger basins [27; 36]. For these two hypothesized Pleistocene lakes, unlike for the Holocene one(s) reconstructed in the southern part of our research area, overflow of the Nile through Wadi Toshka is seen as a likely source of water [52]; cf. Figure 18c,d. The reconstruction of paleolakes has important implications as one may expect groundwater, perhaps shallow, to be found at many places in the past lake location(s). This is exactly the case with our study area in the southern part of the Western Desert, with subsurface water reachable at some places in the area overlapping with the hypothetical lake(s), just a few meters below the present-day surface (Figure 19). In recent years, this groundwater began to be exploited for agricultural reclamation projects, clearly visible on Google Earth, with circular fields watered by sprinklers using water pumped from the aquifer (e.g., El Oweinat project; see Figure 16a) or densely packed watermelon cultivation fields relying more on the near-surface water sources (at or near nos. 2, 5, 6, 13 in Figure 19), e.g., [30]. The strike angles at the southern end of the TK lowland are combed, as expected--see Figure 20--but it is not so intensive as for other places discussed elsewhere in this paper (probably the energy of the stresses on the local material was not so intensive).