Re-evaluating the Development of Phosphorus Loading Restrictions: Maumee River Case Study THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Anna Maria Apostel Graduate Program in Civil Engineering The Ohio State University 2016 Master's Examination Committee: Gajan Sivandran, Advisor Gil Bohrer Michael Durand Copyright by Anna Apostel 2016 Abstract Total Maximum Daily Loads (TMDLs), as established by section 303(d) of the Clean Water Act, have been the metric utilized for the assessment and monitoring of the water quality within watersheds. However, with limited gauge stations on the majority of water bodies throughout the United States, determining waterbody impairment has come to rely on hydrological models. This research analyzes the limitations of the TMDL framework and the limitations of the current state-of-the-science models in the context of the use of adequate datasets as well as the appropriateness of both the models and the imposed regulations to capture the proper processes propagating NPS pollution in the context of the reemergence of Lake Erie algal blooms. The Maumee River basin has been documented as the number one contributing source of nutrients responsible for algal blooms in Lake Erie’s Western Basin. This relationship has seen higher discharge values being correlated to increased algal bloom severity. Three analyses were completed. The first of these was an assessment of potential variability among datasets in order to look at the appropriateness of certain frequencies and lengths and to identify where potential sources of error may exist. Secondly, the impacts of chronic and acute loading were examined in order to solidify the understanding of the impacts of spring storm events and establish a context for a process-based evaluation of loading. Finally, a ratio analysis was performed on the chronic and acute loading components of discharge and loads from the Maumee River to evaluate the effectiveness of the SWAT model to capture the appropriate transport processes the watershed exhibits. The spring events were reaffirmed as the primary indicator of the strength of late summer algal blooms in Lake Erie’s Western Basin, establishing the importance of acute transport events and surface transport mechanisms in this region. Here, March flows correlated with blooms at an R2 of 0.72 with the late summer blooms. Evaluated against SWAT model output, SWAT data showed a shift towards chronic with a March ratio shift ii from 0.62 base/storm for the observed data to 0.95 for the SWAT modeled data. This shift towards baseflow transport processes indicate issues associated with appropriate parameterization in during the calibration and validation process. iii Dedication This document is dedicated to my family. iv Acknowledgments I would like to express my deepest gratitude to my advisor, Dr. Gajan Sivandran, for his guidance throughout my time spent in my master’s program. His patience and constant support were essential throughout my studies. He enabled me to become a better student, a better writer, a better scientist and always encouraged me to look at the bigger picture of what my work means. His endless dedication to his students and field provided me with a consistent source of inspiration to advance and succeed in my work. I will always be grateful for the opportunity he gave me when he chose to take on a student with an unconventional background for the engineering field. I am also grateful to my committee members, Dr. Gil Bohrer and Dr. Michael Durand, for their support. Their insight on my presentations and data analysis was invaluable in the development and advancement of my research progress and success. I would like to thank my research group for providing me with ongoing intellectual support throughout my research process. Joining a new field presents many challenges and the support and understanding I continually received from my group helped accelerate the advancement of my skills and knowledge base in a collaborative environment. A special thank you to James Phelps for the continual support in the development of my coding framework and skills. Additional thanks go to Dr. Noel Aloysuis for providing SWAT model output of the Maumee watershed for the analysis of model effectiveness. I also acknowledge the Heidelberg University National Center for Water Quality Research and the NASA MODIS aqua satellite for making their data available to the public. I would like to thank the Shumate Memorial Fund and the Ohio Water Resource Center for their indispensable financial support throughout my degree. Lastly, I am forever grateful to my family and Matthew Duggins for the continuing personal support throughout my graduate school career. My success has been built off of the support you have provided me and I could not have come this far without you. v Vita June 2010 .......................................................The Wellington School 2014................................................................B.S. Biology, Denison University 2015 to present ..............................................Graduate Research Associate, The Ohio State University Fields of Study Major Field: Civil Engineering vi Table of Contents Abstract .............................................................................................................................. ii Dedication ......................................................................................................................... iv Acknowledgments ............................................................................................................. v Vita .................................................................................................................................... vi List of Tables ..................................................................................................................... x List of Figures ................................................................................................................... xi 1 Introduction ................................................................................................................ 1 1.1 Motivation .............................................................................................................. 1 1.2 Objectives .............................................................................................................. 9 1.3 Hypotheses ........................................................................................................... 10 2 Literature Review ..................................................................................................... 12 2.1 Phosphorus .......................................................................................................... 12 2.2 Lake Erie’s Water Quality ................................................................................... 14 2.2.1 Site Descriptions ........................................................................................... 16 2.2.1.1 Lake Erie ................................................................................................ 16 2.2.1.2 The Maumee River Watershed ............................................................... 17 2.2.2 Algal Blooms on Lake Erie ........................................................................... 19 2.2.3 Why Algal Blooms Appear ........................................................................... 20 2.2.4 Current Work on Lake Erie Algal Blooms ................................................... 21 2.3 Current Water Quality Controls in the United States: TMDLs ........................... 23 vii 2.3.1 TMDL Framework ........................................................................................ 23 2.3.2 Model Choice ................................................................................................ 26 2.3.2.1 Urban and Agricultural Models ............................................................. 27 2.3.2.2 Lake and River Models ........................................................................... 30 2.3.2.3 Equifinality in Models ............................................................................ 30 2.3.3 Acute v. Chronic Loading ............................................................................. 32 2.3.4 Methods of Baseflow separation ................................................................... 34 3 Methods ..................................................................................................................... 39 3.1 Data Description ................................................................................................. 39 3.1.1 Maumee Phosphorus and Flow: Observed Data ........................................... 39 3.1.2 Maumee Phosphorus and Flow: Modeled Data ............................................ 39 3.1.3 Lake Erie Algal Blooms................................................................................ 39 3.2 Data Preprocessing ............................................................................................. 41 3.2.1 Maumee Phosphorus and Discharge ............................................................. 41 3.2.2 Lake Erie Algal Blooms................................................................................ 42 3.3 Length and Frequency Analysis .......................................................................... 42 3.3.1 Data Decomposition.....................................................................................