## Facts

- Small farmers and landowners downstream of Waihee Stream on Oʻahu relied on instream flow to irrigate taro and other crops.
- The municipal Board of Water Supply (BWS) developed tunnel works, shafts, and wells to withdraw groundwater from the Waihee dike complex, a mountain reservoir whose seepage and overflow substantially supply Waihee Stream.
- BWS’s withdrawals reduced streamflow; plaintiffs alleged the reduced flow damaged taro cultivation and contributed to pythium infestation.
- Plaintiffs claimed (1) statutory riparian rights to stream water and (2) appurtenant water rights associated with historical cultivation at the time parcels were converted to fee simple during the Great Māhele era.
- BWS asserted it had acquired water rights and argued that prior Hawaiʻi precedent on water rights should be rejected.
- The trial court issued a permanent injunction barring BWS from reducing Waihee Stream below 2.7 million gallons per day and ruled largely for plaintiffs on riparian and appurtenant rights.
- Both sides appealed; plaintiffs cross-appealed on aspects of the trial court’s measurements and protections.

## Issues

1. Whether riparian rights in Hawaiʻi arise from HRS § 7-1 and, if so, whether such rights can be severed and transferred apart from riparian land.
2. How appurtenant water rights are defined in Hawaiʻi and whether they may be severed or withheld upon conveyance of the land.
3. What showing a riparian owner must make to obtain relief for a diversion that diminishes streamflow.
4. Whether established surface-water rights may be protected against groundwater pumping when surface and groundwater are physically interrelated.
5. Whether prior Hawaiʻi water-rights precedent (including McBryde) remained controlling.

## Decision

- The Supreme Court of Hawaiʻi reaffirmed McBryde as correctly stating Hawaiʻi water-rights law.
- The court held riparian rights in Hawaiʻi are statutory under HRS § 7-1, purpose-limited, and inseverable from the land.
- The court rejected an absolute “natural flow” entitlement and required proof of actual harm to the plaintiff’s reasonable use to obtain relief from a diversion.
- The court defined appurtenant water rights as tied to water used by parcels at the time of original conversion to fee simple; the rights ordinarily run with the land, though a grantor may provide that the benefit will not pass to the grantee.
- The court held that, if surface and groundwater are shown to be parts of a single physical system, surface-water rights may be protected against injurious diversions whether the diversion is of surface water or groundwater.
- The court reversed the injunction and judgment and remanded for recalculation and allocation of rights and for determinations consistent with the reasonable-use and actual-injury standards.

## Legal Principles

- Riparian rights in Hawaiʻi are grounded in HRS § 7-1 and are limited to the purposes for which the statutory rights were established.
- Statutory riparian rights cannot be severed from riparian land or transferred as an independent property interest.
- A riparian plaintiff must show actual harm to the plaintiff’s reasonable use; diminished flow alone is insufficient.
- Appurtenant water rights attach to land based on water use at the time the parcel was converted to fee simple; such rights generally may not be severed or separately transferred.
- A land conveyance may reserve the benefit of appurtenant water rights by providing that the benefit does not pass to the transferee.
- When land is used for traditional cultivation by methods approximating Māhele-era practices, present diversions may support a presumption approximating the quantity of appurtenant rights.
- Hydrologically connected surface water and groundwater may be treated as one system for protecting established surface-water rights against injurious groundwater pumping.

## Conclusion

The court reversed a minimum-flow injunction and clarified that Hawaiʻi riparian rights are statutory, inseverable, and enforceable only upon proof of actual harm to reasonable use; it also refined appurtenant-rights doctrine and confirmed that connected groundwater pumping can be restrained when it injures established surface-water rights.


Reppun v. Bd. of Water Supply, 65 Haw. 531, 656 P.2d 57 (Haw. 1982), cert. denied, 471 U.S. 1014 (1985)