Using Hydrology as a Surrogate in TMDL Development for Impairments Caused by Multiple Stressors

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Advances in Water Resource and Protection (AWRP) Volume 2, 2014 www.seipub.org/awrp

Using Hydrology as a Surrogate in TMDL Development for Impairments Caused by Multiple Stressors Thambirajah Saravanapavan*1, Eiji Yamaji2, Mark Voorhees3, and Guoshun Zhang4 Center for Water Resources, Tetra Tech, Inc., Fairfax, Virginia, USA

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Graduate School of Frontier Sciences, The University of Tokyo, Tokyo, JAPAN

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U.S. Environmental Protection Agency, Region 1, Boston, Massachusetts, USA

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tham.saravanapavan@tetratech.com; 2yamaji@k.u‐tokyo.ac.jp; 3mark.voorhees@epa.gov; guoshun.zhang@tetratech.com

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Received 10 September 2013; Accepted 14 October 2013; Published January 2014 © 2014 Science and Engineering Publishing Company

Abstract

Introduction

Habitat and aquatic life impairments are unfortunate consequences of the urbanization process in many places. In the United States, total maximum daily loads (TMDLs), restoration strategies or plans, are developed to help maintain water quality standards. The development of TMDLs to mitigate habitat and aquatic life impairments, however, presents unique challenges as the impairments are often associated with multiple stressors. While the stressors may vary from specific pollutants, stormwater runoff, hydrologic modifications, riparian corridor encroachment, and channel alteration, the determination of the exact role and relative significance of individual stressors leading to the impairment and the subsequent development of TMDLs for corresponding pollutants are often technically and financially challenging. An innovative approach of using hydrology as a surrogate in developing TMDLs for mitigating habitat and aquatic life impairment caused by multiple unspecified stressors was introduced in this study. The approach directly addresses the ultimate driving force of many stressors (pollutant loading, habitat destruction and hydrologic alteration) causing habitat and aquatic life impairment, namely the excess stormwater runoff. Applications of the innovative approach for quantifiable habitat and aquatic life TMDL development have been demonstrated through two case studies, one in the Shawsheen watershed of Massachusetts, USA and the other in the Indian Brook watershed of Vermont, USA. The results indicated that the approach can effectively facilitate the development of TMDLs for impairment situations characterized by multiple unknow stressors and limited data.

Natural river flow conditions around the world have been negatively impacted as the trend of urban sprawl continues to accelerate (Chen and Wu, 1987; Sparks, 1992; Dynesius and Nilsson, 1994; Walker et al., 1995). Changes in flow conditions directly influence river biota, especially the habitat and aquatic life (Ward and Stanford, 1979, Petts, 1984; Calow and Petts, 1992). For example, organisms that are sensitive to flow velocity, including periphyton, phytoplankton, macrophytes, macroinvertebrates, young fish and deposited eggs, are easily displaced as a result of increased frequency or duration of high flow levels (Moog, 1993; Allan, 1995). Channelization and dredging, as well as riparian vegetation elimination all modify the habitat (OEPA, 2012). At the same time, pollutants discharged into rivers and other receiving water bodies also cause adverse biological effects: infection of organisms by bacteria and viruses, increased biological oxygen demand (BOD) and lower dissolved oxygen (DO), death from chronic toxicity exposure and alteration to natural habitat cycles and breeding, etc. (Zoppou, 2001; Whitehead et al. 2006). In fact, habitat alteration and impaired biota have been the leading causes of impairment in assessed United States rivers and streams for many consecutive years, regardless of designated uses (USEPA, 2007, 2009).

Keywords

In the United States, the total maximum daily load (TMDL) program has been established by the Clean Water Act (CWA) to address water quality issues in

Urbanization; TMDL; Surrogate Indicators; Stormwater Management; Aquatic Life Impairments; Multiple Stressors

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