Nutrient Mass Balance Study for Ohio's Major Rivers
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Nutrient Mass Balance Study for Ohio’s Major Rivers Division of Surface Water Modeling and Assessment Section APRIL 16, 2018 State of Ohio Nutrient Mass Balance Study April 2018 Table of Contents Executive Summary ......................................................................................................................................................................................................... 2 Background and Purpose ......................................................................................................................................................................................... 2 Important Findings ..................................................................................................................................................................................................... 2 Future Actions ............................................................................................................................................................................................................... 4 1 Introduction ..................................................................................................................................................................................................................... 4 Past Studies and Associated Work ....................................................................................................................................................................... 6 2 Methods ............................................................................................................................................................................................................................. 8 2.1 Overall Loading Calculation............................................................................................................................................................................. 8 2.2 Point Source Loading .......................................................................................................................................................................................... 8 2.3 HSTS Loads ............................................................................................................................................................................................................. 9 2.4 Nonpoint Source Loading .............................................................................................................................................................................. 11 2.5 Pour Point Load Estimation ......................................................................................................................................................................... 12 3 Results and Discussion ............................................................................................................................................................................................ 12 3.1 Statewide Analysis ............................................................................................................................................................................................ 12 Watershed Area ......................................................................................................................................................................................................... 13 Relationship of Annual Water Yield to Annual Load ................................................................................................................................ 13 Nonpoint Source Nutrient Yield ......................................................................................................................................................................... 17 Per Capita Nutrient Yield ...................................................................................................................................................................................... 18 Population Density ................................................................................................................................................................................................... 18 Relative Loadings...................................................................................................................................................................................................... 18 3.2 Maumee River ..................................................................................................................................................................................................... 21 3.3 Portage River ...................................................................................................................................................................................................... 31 3.4 Sandusky River ................................................................................................................................................................................................... 35 3.5 Frontal Lake Erie Tributaries ...................................................................................................................................................................... 39 3.6 Vermilion River .................................................................................................................................................................................................. 42 3.7 Cuyahoga River .................................................................................................................................................................................................. 45 3.8 Great Miami River ............................................................................................................................................................................................. 49 3.9 Scioto River .......................................................................................................................................................................................................... 53 3.10 Muskingum River ........................................................................................................................................................................................... 57 4 Summary and Future Work ................................................................................................................................................................................... 61 Acknowledgements ....................................................................................................................................................................................................... 63 References Cited ............................................................................................................................................................................................................. 64 Appendix A - Spring Nutrient Loading for Selected Lake Erie Tributaries .......................................................................................... 67 Maumee River ............................................................................................................................................................................................................ 68 Portage River .............................................................................................................................................................................................................. 69 Sandusky River .......................................................................................................................................................................................................... 70 Appendix B – Summary Tables for Mass Balance Calculations ................................................................................................................. 71 Appendix C - Summary of Initiatives to Address Nutrients and Harmful Algal Blooms ................................................................ 81 Page 1 of 82 State of Ohio Nutrient Mass Balance Study April 2018 Executive Summary Background and Purpose Excess nutrients (nitrogen and phosphorus) stimulate algal growth affecting water quality. Ohio EPA completed this study to identify the most environmentally beneficial and cost-effective mechanisms for nutrient reduction. For example, if nonpoint source nutrients are found to be the major contributor of downstream total phosphorus load, as is the case in the Maumee River and other northwest Ohio watersheds, then only focusing remediation on point source nutrients would neither be prudent or efficient to protect downstream waters. While it is too early to detect statistically sound trends, the results of this study show no clear decrease in loading yet, especially in nonpoint source dominated watersheds like the Maumee where the loading in 2017 was the highest of the years reported. This study, along with the other data related to current and past nutrient loadings, can and should serve as a tool to focus research, investment, and policy/legislation decisions to curb phosphorus and nitrogen loading in both the Lake Erie watershed and the Ohio River basin. This mass balance study computes annual total nitrogen (N) and phosphorus (P) loads originating from Ohio watersheds draining to Lake Erie and the Ohio River. The 2016 edition included