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Oklahoma applies the reasonable use rule for water drainage. This rule states that a landowner can make "reasonable" alteration to the drainage pattern of his parcel, with liability only occurring when the alteration causes "unreasonable" harm toward neighboring parcels.
I am guessing the dam is manmade. If so, then it can be argued that based on the above, the 25% owner has a duty to maintain the dam. If they do not, then they may be sued for negligence.
However, if the dam is not man made and is natural, then another answer would apply - reply and let me know.
Citations: Iven v. Roder, 431 P.2d 321, 328 (Okla. 1967). Dobbs v. Missouri Pacific R.R., 416 F. Supp. 5, 9 (E.D. Okla. 1975)
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