MT SB358

Establishes "legislatively designated controlled ground water areas" in Gallatin Valley, Helena Valley, and Missoula Valley aquifers where ground water appropriation requires a permit, with limited exceptions for single living units (up to 0.5 acre-feet/year) and stockwater

Creates "legislatively designated temporary controlled ground water areas" in Flathead Valley, Billings terrace level 3, and Bitterroot Valley aquifers requiring mandatory metering and semiannual reporting of water usage with annual department review

Revises criteria for designating water quantity controlled ground water areas, requiring closure when well density exceeds 150 wells per square mile and aquifer appropriation exceeds 80% of available water or surface water demand exceeds physical availability

Requires the Department of Natural Resources and Conservation to conduct a statewide analysis by December 31, 2026 to identify suspected noncompliant water use, notify landowners, and pursue judicial enforcement after December 1, 2028

Removes previous restriction preventing metering requirements on wells outside controlled ground water areas and changes reporting requirements from annual to semiannual for new water rights in designated areas