Presenter/s: John McLaren
Symposium Session: 2024 - 10 Big Scale Hydrology - Redefining Stream Power
Topics covered: flow augmentation, hydraulics, and idaho
ABSTRACT
Restoration action often seeks to remove anthropogenic alterations to the physical or hydrological structure of a stream ecosystem. However, aggressive restoration actions are often unrealistic in larger waterways given ongoing human reliance on waterways for critical infrastructure, including irrigation, power generation, and municipal use, and the legal and administrative structures that prioritize such uses. In the Henry’s Fork of the Snake River in eastern Idaho, the benefits of a functioning ecosystem are subservient to the needs and legal requirements of irrigated agriculture. To produce measurable ecological benefits, conservation organizations such as the Henry’s Fork Foundation must work within existing legal and physical infrastructure. The Henry’s Fork Foundation accomplishes restoration through intensive monitoring which guides collaborative action. The Henry’s Fork Foundation identified key hydrological drivers of fish and invertebrate populations, targeted management flexibilities that could affect those drivers, then worked with irrigation districts, individual irrigators, and state and federal agencies to achieve conservation objectives. For example, improving precision in water management and incentivizing reduced irrigation consumption has reduced the use of water in a storage reservoir by almost 50% relative to water supply. The savings increased annual winter flow, decreased annual summer flow, and allowed a managed springtime freshet in three of the last five years despite long-term drought conditions. These actions have improved water quality, macroinvertebrate indices, and increased fish populations up to 150%. Reductions in water consumption are just the beginning; ongoing monitoring indicates the possibility to use irrigation water for intentional and incidental managed aquifer recharge. Managed aquifer recharge would improve water quality and fish and macroinvertebrate populations on both the local and watershed scale. The experience and successes of the Henry’s Fork Foundation may prove useful for other large “working” river systems across the western U.S.