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Eva Sinha

Eva Sinha, P.E.

esinha@stanford.edu
PhD Candidate, Department of Earth System Science





I study how human-caused climate change can impact water quality. The impact of climate change on precipitation amount, intensity, and the occurrence of extremes has been well established, however, its impact on water quality is still not well understood. Degraded water quality can negatively impact both human and ecosystem well-being. My research focuses on how changes in precipitation patterns owing to climate change, will impact nutrient loading, which in excess is one of the major drivers of impaired water quality.


Research Highlights


Eutrophication will increase during the 21st century as a result of precipitation changes

E. Sinha, A.M. Michalak and V. Balaji Science

Excessive nitrogen inputs, or eutrophication, from rivers is a major cause of harmful water quality problems such as algal blooms or hypoxic dead zones. In this manuscript we analyzed how changes in precipitation patterns will impact future riverine nitrogen loading by utilizing precipitation projections from 21 climate models for three different emission scenarios. Anticipated changes in precipitation patterns are found to cause large and robust increases in nitrogen fluxes by the end of the century by the end of the century for the “business-as-usual” scenario and these impacts will be the strongest for the Northeast and the corn belt of the United States.

Figure: Projected changes in mean total nitrogen flux for watersheds within the continental United States for the RCP8.5 "business-as-usual" emission scenario. (A) Total nitrogen flux for the historical period (1976–2005), averaged across 30 years and 21 CMIP5 models. (B and C) Projected change in mean total nitrogen flux for the near future (2031–2060) and far future (2071–2100) relative to the historical period. For (B) and (C), stippling highlights watersheds with a robust change in total nitrogen flux (i.e., more than 50% of the models show a significant change and more than 80% of the models agree on the sign of change). Watersheds with inconsistent projections (i.e., more than 50% of the models show significant change but fewer than 80% of the models agree on the sign of change) are shown in white. Remaining watersheds are shown in color without stippling. The black outlines highlight the upper Mississippi Atchafalaya River Basin and the Northeast region.

Sinha, E., A. M. Michalak, V. Balaji (2017) "Eutrophication will increase during the 21st century as a result of precipitation changes," Science, 357 (6349), 405-408, doi:10.1126/science.aan2409.


Precipitation Dominates Interannual Variability of Riverine Nitrogen Loading across the Continental United States

E. Sinha and A.M. Michalak Environmental Science & Technology

Excessive nitrogen in waterbodies can result in eutrophication and increased occurence of impaired water quality problems such as the occurrence of harmful algal blooms and low dissolved oxygen concentration. In this manuscript we developed an empirical modeling tool that provides the first comprehensive estimates of riverine total nitrogen load for a 21-year period. We found that the spatial distribution of the nitrogen load is governed by nitrogen inputs to the land but the large year-to-year variability in loading is primarily due to year-to-year changes in precipitation.









Figure: Difference in total nitrogen loading from long-term mean for HUC8 watersheds, illustrated for years with minimum (1988) and maximum (1990) estimated total loading for continental United States within the period 1987-2007.

Sinha, E., A. M. Michalak (2016) "Precipitation Dominates Interannual Variability of Riverine Nitrogen Loading across the Continental United States," Environmental Science & Technology, 50 (23), 12874-12884, doi:10.1021/acs.est.6b04455.