Impacts of low summer streamflows on water resources in the Jefferson Valley : historical responses and future challenges

Abstract

In an attempt to understand the complex interrelationships between climate, water infrastructure regimes, and water governance this thesis examines relationships between drought and water use in the Jefferson River Basin in southwest Montana. The Jefferson River is one of the three great headwater streams of the Missouri River and is itself comprised of the Beaverhead, Big Hole and Ruby Rivers, encompassing a substantial drainage basin of 9,532 sq. miles. The Jefferson's unique hydrological position inherently situates the basin "at the end of the line" of water users and flows at its confluence have plummeted to 200 cubic feet per second (cfs) during extreme drought periods, leaving little water in the river to appease appropriators along the river's remaining 80 miles. The Jefferson River (and all of its important tributaries) is highly utilized for agriculture, resulting in chronic dewatering during peak irrigation demand (typically July through mid-September). Persistent water scarcities over the last 15 years have tested the Basin's ability to sustain historic levels of agricultural production and maintain a commercial sports fishery. This thesis provides a resilience assessment of water resources in Jefferson Basin. RA's attempt to conceptualize dynamic interactions between linked social and ecological systems (SES's). Analysis of complex human use systems (SES's) is inherently interdisciplinary and necessitates a mixed methods approach. The RA completed for this thesis integrated physical analyses of the water use system (utilizing GIS, hydrology, climate and demographic data) with a qualitative survey of water stakeholders with the goal of understanding the processes that drive the Jefferson SES and identifying weaknesses that reduce resilience. Over the last 30 years the Jefferson Basin has benefited from a unique subset of water users and natural resource managers that have successfully worked to improve conditions in the face of extreme environmental challenges. This RA found that although it is highly likely that the Jefferson will be challenged by extreme conditions in the future (related to a changing climate), it is also evident that there is potential for the basin to transition into alternate and more resilient regimes.