The clearest lesson from this long-running practice is that the value of subsurface investigation became apparent only gradually: for most of SDCMR's history, check dams and cisterns were sited largely on surface topography and local knowledge, without systematic subsurface data. The more recent introduction of ERT and TEM surveys by the DRC Geophysical Exploration Department — applied, for example, in the Fuka Basin and at Ras El Dabaa (Elshenawy; Zarif et al., 2024) — has shown that resistivity data can flag clay-rich zones or saline intervals that are not obvious from the surface, information that would have been useful earlier in the programme's history. A second, more straightforward lesson is logistical: remote wadi locations with limited road access materially increase both construction and monitoring costs, and should be budgeted for explicitly rather than assumed away.