## 4 Paleolakes and Groundwater
### Hypothetical Paleolake between Kharga and Toshka
For an easy orientation in the problem to reconstruct the paleolake, we used \(\Delta g\) from Figure 17b and added the contour lines for 150, 200 and 250 m asl from the topography in Figure 17a. The result is presented in Figure 18a-c. The contour lines separately without the topography are shown in Figure 18d for 200, 170, 150 and 120 m asl. Large expanses at 250 and 200 m are replaced by the break-up of one large lake (its shallower southern part) into a few smaller lakes at 170 and 150 m asl and, finally, at 120 m, only the northern deeper zone remains with water. Figure 18e,f show the position and extent of the hypothetical paleolake based on the assumptions and estimates. The paleolake would include five of the endorheic Toshka lakes from the late 1990s at \(\varphi\) = 23-23.5\({}^{\circ}\) formed due to anthropogenic diversion of the water from Lake Nasser via the Sadat Canal (Figures 18e and 19; Google Earth permits an independent check of the time series satellite images showing the progressive shrinking of the lakes) and the large depression of the Kharga Oasis. The paleolake would be huge. Its northern part (within Kharga) would be the deepest. The southern, shallower part would be more prone to water level variations and desiccation. The available archaeological data from the Toshka-Kiseiba depression allow us to test the hypothesis of the existence of a large lake in the southern part of the Western Desert of Egypt and to attempt to constrain its extent and position. Figure 18e shows all 12 sites from Table 1 plotted onto the map, with the _ETOPO 1_ topography showing the position and extent of the hypothetical lake at 200 m asl and the contour lines for 170, 150 and 120 m asl. Of the sites, two Holocene locations (nos. 2, 7) are situated away from the 200-meter contour and the shore of the hypothetical lake. Three sites (nos. 3, 4, 10), including the only Pleistocene (Lower Paleolithic, no. 3) location, are positioned near the 200-meter contour (at 200, <180 and 190 m asl, respectively). The remaining seven sites, all of Holocene dating, are located between the 200- and 170-meter contours, with three areas (nos. 5, 6, 9) positioned close to and two (nos. 8, 12) even below the 170-meter contour. This distribution rules out a Holocene age for a large lake at 200 m  
Figure 19: The positions of modern excavated wells (black dots) in the southern part of the Western Desert, indicating the location of known present-day groundwater. 1—Bir Abu Hussein, 2—[PERSON], 3—[PERSON], 4—[PERSON], 5—[PERSON], 6—[PERSON], 7—[PERSON], 8—[PERSON], 9—[PERSON], 10—[PERSON], 11—[PERSON], 12—[PERSON], 13—[PERSON] (locations plotted using the coordinates at [54]. The present-day Toshka lakes are shown as blue dots (the same as in Figure 18e). asl, as most of the settlements would end up submerged by its waters. For this period, one may allow only for the existence of a smaller lake--or, rather, a system of lakes--in the southern section of the area of interest, with the water levels reaching generally between \(\sim\)170 and \(\sim\)180 m asl. Despite the clear correlation of many (if not all) Holocene occupation areas with the proposed height of the water level of the hypothetical lake(s) at \(\sim\)170 and \(\sim\)180 m asl, diverse evidence suggests variation in the lake levels on diverse scales during the Holocene. First, there are clear long-term changes in the availability of water between the Early and Middle Holocene (see Table 1). In the former period (before 8200 BP), there is an increase in the number of occupied sites from seven in the earlier phase (\(\sim\)9500-8200 bp) to ten during the local climatic optimum (\(\sim\)8050-7300 bp). This increase is accompanied by a shift from seasonal occupation by mobile foragers in the earlier phase to reduced mobility and stabilization of the settlement system (large settlements, wells) and intensified use of local resources (plant foods, storage) by intensive collectors in the later phase.