Chlorine-36 ages (Paterson et al., 2005) show a progression with distance over the Dakhla Basin eastward from 210-230 kyr in Dakhla reaching ~600 kyr in Kharga and northeastward to 320 kyr in Farafra and 700 kyr in Bahariya (Fig. 5). 36Cl/Cl ratios vertically indicate long, deep flowpaths of the paleorecharge near the southern highlands of the Uweinat area. Late Quaternary recharge appears to affect the shallow aquifer horizons only (Paterson et al., 2005).
Krepton-81 ages (Sturchio et al., 2004) show also a progressive increase with distance to the east and north from the Dakhla Oasis, their spatial distribution indicates relatively high flow velocities (~1 m/yr–3.17×10-8 m/s) from Dakhla (210 kyr) toward Farafra (330 kyr) along the groundwater flow, and low velocities (~0.2 m/yr–6.34× 10-9 m/s) from Dakhla toward Kharga and Baris (490-680 kyr), and from Farafra (330 kyr) toward Bahariya, Bauti-1 (~1000 kyr; Fig. 5). These ages were interpreted as a local recharge through regional precipitation in the Uweinat area near the Egyptian/Sudanese border (Sturchio et al., 2004; Paterson et al., 2005).
Chlorine-36 groundwater ages increase progressively eastwards from Siwa to Qattara (Gara) ~ 114 kyr; and northeastwards form west Farafra to north Bahariya by ~ 640–715 kyr (Fig. 5). Their spatial distribution indicates relatively high flow velocities (~0.66 m/yr–2.09×10-8 m/s) from Siwa to Qattara (Gara), and from northwest Farafra to north Bahariya (~0.4 m/yr–1.27×10-8 m/s)