(taxpayer proposed to make charitable contribution of taxpayer's "appropriative interest" in water rights; such interest treated as separate property interest under state law, but contribution of less than taxpayer's entire interest in property not deductible unless it is a remainder interest in annuity or unitrust, taxpayer's undivided interest in entire property, a remainder interest in a farm or residence or a conservation easement; unidentified Rev. Rul. (probably Rev. Rul. 88-37 (overriding interest in oil and gas lease same as underlying working interest)) referenced leading to conclusion that interest at issue not to be treated as distinct property interest from taxpayer's underlying water right and that deduction not allowable; second ruling notes that taxpayer should have argued that contribution was of a conservation easement because conservation easement deductible under partial interest rule because it is considered to be gift of undivided portion of donor's entire interest in subject property (Treas. Reg. Sec. 1.170A-7(b)(1)(ii)).