Date of Award

Spring 1-1-2011

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Edith Zagona

Second Advisor

Balaji Rajagopalan

Abstract

One aspect of integrated water resources management is the sustainable management of river systems to preserve ecosystems. Historically, environmental flow (e-flow) requirements were specified as a minimum allowable flow, though recent research has suggested that all aspects of a flow regime are ecologically important. To better reflect the natural variability of the river system, e-flows now vary from year-to-year and include target baseflows and flood pulses. Many required e-flows are for reaches directly below reservoirs, where human abstractions have degraded the natural variability of the rivers but management can help sustain the river ecosystem through modifications to reservoir operations. In order to understand the reliability of meeting complex e-flow requirements in the future, e-flows need to be incorporated into a long-term planning model where the reliability can be analyzed. Since planning models operate at the monthly timescale and e-flows are stated in days the integration is not directly achievable.

This research aims to address the scale issues associated with integrating e-flow requirements into planning models. Since reservoir operations are required to meet e-flow targets, the focus is on incorporating complex sub-monthly reservoir operations into a planning model. This requires multiple facets: 1) The temporal scale issues that exist between daily e-flow requirements and the monthly operations of the reservoirs in the model must be resolved. 2) Reservoir releases rely on unregulated tributaries to sustain higher downstream e-flow targets, thus daily flows from the unregulated tributaries are also necessary. 3) Hydrologic year types guide reservoir operations to meet different e-flow targets, thus they must be incorporated into the model to capture reservoir operations. Finally, after addressing the integration of new reservoir operations into the planning model, flow alteration -- the degree to which a river is departed from a baseline state -- is presented as a metric for the reliability of meeting e-flows.

Through an example application on the Colorado River Basin, the techniques are demonstrated to have utility. The successful incorporation of daily reservoir requirements into a monthly model is a key result. Further results under multiple supply and demand scenarios are used to highlight the key components in the modeling framework and to demonstrate their use under a nonstationary climate.

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