Short answer. No. Article 509 is flat: no one may enter private property to search for waters or make use of them without the owner's permission, subject only to what the Mining Law provides. Needing the water, or believing the source runs under your land, gives nobody a right of entry.
What the law says
No one may enter private property to search waters or make use of them without permission from the owners, except as provided by the Mining Law.
Civil Code, Article 509 — No Entry To Search For Waters. Read the full provision →
The rule covers looking as well as taking
Two separate acts are prohibited: entering to search waters and entering to make use of them. That first limb matters, because the usual opening move is exploratory — a crew sinking test holes, running a survey, tracing a spring uphill — and it is often defended on the footing that nothing has yet been extracted. Under this article that defence fails. The prospecting itself requires your permission, so you are entitled to object at the survey stage rather than waiting until a well is producing and the argument has become about an investment already made.
Permission means yours, and it is worth being specific about
The article says permission from the owners, in the plural where the property is held by more than one, so consent given by a co-owner, a caretaker, a tenant or a relative on the premises is not the article's permission. Nor is acquiescence: letting a crew onto the land once for a stated purpose is not a standing licence to return, deepen a hole or connect a line. If you do agree to anything, put the scope, the duration and the purpose in writing, because a vague permission is the thing most often relied on afterwards to justify a great deal more.
The exception is narrow, and it is not a general utility exception
The only carve-out named is the Mining Law. That is a specific regime with its own permits and its own conditions, and a party invoking it should be able to identify what it holds under that law. Being a large company, a water district or a contractor for a public project is not what the article excepts. Where a genuine legal basis for entry exists elsewhere, it will come with paperwork; the sensible first response to any demand for access is to ask for that paperwork rather than to argue about the water.
What to do while it is still a trespass and not a fixture
Act early, because the practical dynamics change once equipment is installed. Record what you find — dated photographs of the crew, vehicles, markings and any boring, and the exact location on your lot — and object in writing to whoever is responsible, keeping proof it was received. Ask on what authority the entry is made and get the answer in writing too. If drilling has already happened, the position of the works relative to your boundary is a survey question, and having it fixed by a licensed surveyor early is what makes everything afterwards provable.