Short answer. No — not without the owner's permission. Under Article 512 of the Civil Code, only the landowner or a person with the landowner's permission may explore for subterranean waters. On public land, permission must come from the administrative authorities. The Mining Law may also apply in some situations.
What the law says
Only the owner of a piece of land, or another person with his permission, may make explorations thereon for subterranean waters, except as provided by the Mining Law.
Civil Code, Article 512 — Exploring For Subterranean Waters. Read the full provision →
The default rule: owner or authorized person only
Article 512 establishes that exploring for subterranean waters is an exclusive right tied to land ownership. Only the landowner, or someone expressly authorized by the landowner, may conduct such explorations. A neighbor, a utility company, a private contractor, or even a government agency cannot simply dig on another person's private land to search for groundwater without that owner's permission. The right to explore follows the right to own — it is one of the incidents of land ownership.
Permission can be given — and should be in writing
The landowner can authorize a third party to explore for subterranean water on the land. Article 512 does not specify the form of this permission, but because explorations can be disruptive — drilling, excavation, testing — and because disputes about scope often arise, written permission describing what is allowed and what conditions apply is far more prudent than a verbal understanding. If the landowner later revokes informal permission and disputes what was agreed, the party who relied on verbal authorization may have little to stand on.
Public land: a different authority
When the land in question is part of the public domain — government-owned land that has not been titled to any private person — the rule changes. Article 512 provides that explorations for subterranean waters on lands of public dominion require the permission of the administrative authorities. The landowner is the government in that case, and the relevant administrative body must grant its approval before any exploration activity begins. What specific agency governs depends on the classification and location of the public land.
The Mining Law exception
Article 512 contains a carve-out: its rule applies except as provided by the Mining Law. Legislation governing mineral resource extraction may create pathways for exploration and extraction that operate on different authorization rules, particularly for resources deemed part of the country's natural wealth. If the situation involves more than groundwater — mineral deposits, geothermal resources, or other subsurface resources covered by separate laws — those specialized legal frameworks would govern, not Article 512 alone. In a straightforward dispute about who may drill a well on private land, Article 512 applies directly.