Both Oman and Iran possess a harsh environment where people’s survival and development entail a deep knowledge about their surroundings. A considerable part of this knowledge has crystallized around the falaj, a hydraulic technique that transfers water from a groundwater source or seasonal runoffs to cultivated lands, in Omani and Iranian oases, that has historically served as the only water source in an otherwise barren arid land. This article argues that the spatial extent of the falaj confronts local communities with a variety of questions to be solved. This article also tries to answer how the falaj system contributed to the development of modern sciences in a broader context. The article concludes that a transition from Indigenous knowledge to modern sciences has changed the position of local communities from coexistence to over-exploitation in terms of their water resources, and this transition can explain their current water problems.