Date of Award:


Document Type:


Degree Name:

Master of Science (MS)


Civil and Environmental Engineering

Committee Chair(s)

Bethany T. Neilson


Bethany T. Neilson


Mathew P. Miller


Tiangfang Xu


Streams in urban and agricultural environments are often heavily diverted for irrigation and drinking water purposes. These streams can receive inflow from unmeasured sources including stormwater returns, groundwater drains, and irrigation runoff that will help sustain flow during dry periods. Due to an inability to identify the source of most of these inflows or directly measure their volumes, there is a clear need for identification and quantification methods. Streamflow data from the Logan River Observatory illustrates the importance of unidentified inflows in sections influenced by large diversions. To understand the role of unidentified inflows and possible outflows in this portion of the Logan River, we first collected ion samples from a subset of representative inflow sources and then applied clustering analyses to establish a categorization scheme. Representative concentration ranges for each category of inflow sources, combined with ion samples and streamflow measurements of the Logan River were used in a system of equations to calculate both inflow and loss volumes. The calculated inflows and losses were observed to be most influential at maintaining flow downstream of large diversions and at times of low streamflow in the summer and fall. This highlights the need to better understand and quantify inflow sources. As management practices become more efficient, without an understanding inflow sources and contributions, a portion of these inflows could unknowingly be diminished or eliminated and no longer sustain stream flows during dry periods.