Eastern Snake Plain Aquifer (ESPA)

Most western states leave owners to infer that leasing protects a right. Idaho says so in statute. Idaho Code section 42-1764 provides that water rights credited to the Water Supply Bank are not subject to forfeiture for nonuse while retained in or rented from the bank, and that the five-year nonuse period begins to run anew upon removal of a right from the bank, provided no period of nonuse had already accrued before it was accepted.

The same section provides that approval of a rental from the bank may substitute for the transfer proceeding requirements of section 42-222. In plain terms: banking can both protect the right and spare you a full transfer case.

Two separate published schedules operate here, and they price differently.

The Idaho Water Supply Bank rents at a posted $33 per acre foot from 2025 (up from $23 through 2024). The Board retains 10 percent of gross rent for administration and the lessor receives 90 percent, about $29.70 per acre foot. There is no fee to apply to rent; the lease application fee is $250 per water right, capped at $500 for stacked rights.

Water District 1 publishes a full tier schedule for its rental pool, and the tiers turn on whether the reservoir system fills.

Idaho administers surface and groundwater together. When the Surface Water Coalition’s delivery call finds a shortfall, junior groundwater users must either hold an approved mitigation plan or curtail, and mitigation obligations are denominated in acre feet of storage water secured through private leases.

The 2024 Stipulated Mitigation Plan, approved January 3, 2025, is the operative settlement. It runs January 1, 2024 through December 31, 2027 between the seven-member Surface Water Coalition and nine groundwater districts, carries a collective conservation obligation of 205,000 acre feet per year, and gives compliant districts and their patrons safe harbor from the delivery call.

That obligation shows up as real transactions. Water District 1 publishes a ledger: in 2026 it recorded 40,000 acre feet between IGWA and the Shoshone-Bannock Tribes, 22,000 acre feet between IGWA and the Water Resource Board, and private leases of 10,000, 5,000 and 3,500 acre feet into the Bonneville-Jefferson district, among many smaller ones. Volumes are public; the negotiated prices are not.

2026 was the hardest year of the sequence. The April methodology order predicted an in-season shortfall of 181,600 acre feet, against 74,100 in 2024 and 63,000 in April 2025.

On May 14, 2026 the Director ordered curtailment of groundwater rights junior to October 11, 1900 within the ESPA Area of Common Ground Water Supply. Roughly 930 rights were identified as uncovered by a mitigation plan; by the July mid-summer order IDWR had addressed 87 percent of them with another 11 percent under investigation, and the curtailment date was unchanged.

The water supply explains it: the June joint forecast put unregulated flow at the Heise gage for June and July 2026 at 900,000 acre feet, about 50 percent of normal, down from roughly 70 percent in the April forecast.

IDWR briefed the Board on August 26, 2026. The ESPA had no change in volume from 2024 to 2025, and then a net reduction of 600,000 acre feet this year, measured across 329 monitoring wells before the irrigation season. Spring flows at Thousand Springs and in the Blackfoot to Minidoka reach are expected to decline.

The mitigation programs are working, just not fast enough to offset a dry year. Modeling attributes a combined net storage gain of 2.8 million acre feet to Board recharge, private recharge and pumping reductions, with ten-year retention of 53 percent for Board recharge, 25 percent for private recharge, and 47 percent for pumping reductions.

Surface storage tells the same story: the Upper Snake reservoir system did not fill in either 2025 or 2026, and sat at 18 percent of capacity on August 26, 2026, drafting about 21,000 acre feet a day with carryover on pace to be very low.

If your right is senior, you are holding the scarce asset in a basin where juniors are legally obligated to find water. That is the strongest lease position in the West, and the demand is statutory rather than speculative.

If your right is junior and unused, bank it before the nonuse clock matters. The statute protects banked water from forfeiture and the posted rate gives you a floor without negotiating.

Either way, know which door you are using. The state bank pays a posted rate with 90 percent to you; the Water District 1 pools pay published tiers; a private lease pays whatever you negotiate and returns 100 percent of the price to the lessor, with the buyer carrying the surcharge and admin fee on top.