Nutrient Retention in Restored Streams and Floodplains: A Review and Synthesis

Transcription

1 Nutrient Retention in Restored Streams and Floodplains: A Review and Synthesis Tammy Newcomer Johnson, PhD Environmental Protection Agency Mid-Atlantic Chapter International Erosion Control Association September 21, 2016

2 Acknowledgements Sujay S. Kaushal, UMCP Paul M. Mayer, EPA Rose Smith, UMD Gwen Sivirichi, ARKF Inc. Michael Pennino, EPA Walter Boynton, UMD Peter Groffman, Cary Institute Jeff Cornwell, UMD Philippe Vidon Jim Markwiese, EPA Shuiwang Duan, UMD Melanie Harrison Okoro, NOAA Jonathan Jeschke Michael Craghan, EPA

3 Outline 1 Background 2 Literature Review 3 Nutrient Spiraling 4 Conclusions

4 Terrestrial Nitrogen Fixa on (millions of tons) Humans doubled terrestrial N and P in 20 th Century 150 Total Nitrogen Fixed By Human Ac vi es 100 Es mate of Natural Nitrogen Fixa on Nitrogen Fer lizer 50 Fossil Fuels Legume Crops Year 1990 Source: Vitousek et al; Ecological Applications 1997

5 Now >400 Eutrophic Dead Zones Worldwide Diaz and Rosenberg (2008) Science

6 Chesapeake Chronic Dead Zone EPA s Total Maximum Daily Load (TMDL) pollution diet set to reduce nutrients: 25% for N 24% for P 20% for sediment Dead Zone Urban stream restoration is one of many possible strategies Urbanization can eliminate nutrient sinks Riparian development Stream burial Floodplain disconnection Map from Chesapeake Bay Program

7 Dramatic Loss of Headwater Streams Source: Elmore and Kaushal; FEE 2008

8 Crumbling Infrastructure Across the US Photos from Dr. Sujay Kaushal, UMCP

9 Billions Spent on Stream Restoration Bernhardt and Palmer (2005)

10 Collins et al. (2010) Ecological Engineering

11 Denitrification NO 3- NO 2- NO N 2 O N 2 - Anaerobic - Heterotrophic (requires organic C) Key component of the water quality maintenance function of riparian zones.

12 Outline 1 Background 2 Literature Review 3 Nutrient Spiraling 4 Conclusions

13 Selection Criteria for Study Inclusion Peer-reviewed papers ( ) Primary Search: (1) study ecosystem (river, wetland, ditch, stream, floodplain) (2) management actions (restor*, engineering, rehabilitation) (3) nutrients measured (nitr* or phos*) Secondary Screening: Explicitly examines stream restoration project(s) Must be flowing freshwater system

14 Number per year A Growing Field of Study (a) 550 peer-reviewed publications about stream restoration (b) 79 empirical nutrient studies about stream restoration (c) World map showing 79 empirical nutrient studies from North America, Europe, and Asia 17 studies (22%) are from the Mid-Atlantic Maryland 12 Virginia 2 New York 2 Pennsylvania 1 Newcomer Johnson et al. (2016) Water

15 Restoration Typologies that Increase Hydrologic Connectivity Newcomer Johnson et al. (2016) Water

16 Positive Overall Study Ratings Decreased nutrient concentration/load Increased nutrient retention rate Negative Increased nutrient concentration/load Decreased nutrient retention rate Neutral No significant change

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18 Strategies Used to Increase Hydrologic Connectivity Strategies Typologies Included from Figure 2 Number of Results from 79 Studies Positive Results (%) Neutral Results (%) Negative Results (%) Floodplain Reconnection Streambed Reconnection Increased Stream Surface Area ABCD 62 60% 28% 12% EF 9 70% 20% 10% G 19 65% 22% 13% Increased Wetland Surface Area HI 24 75% 14% 11% Total % 26% 12% Newcomer Johnson et al. (2016) Water

19 Percentage of Studies Number of Studies What happens 50 when projects apply multiple typologies? R 2 = Number of Typologies per Study 100% 80% 60% Posi ve Results Neutral Results Nega ve Results R 2 = % 20% 0% Number of Typologies per Study

20 Methods Used to Evaluation Nutrient Retention Denitrification 31% 96% Mass Balance 22% Change in Nutrient Concentrations Nutrient Spiraling 21% Alternative Methods Used Other Stable Isotope Ratios Nitrification 4% 3% Plant Dynamics 4% Sediment Dynamics 9%

21 Outline 1 Background 2 Literature Review 3 Nutrient Spiraling 4 Conclusions

22 Intensive Nutrient Spiraling Meta-Analysis

23 What is Nutrient Spiraling? S = spiraling length (m) S W = distance solute is in water column S B = distance solute is in biota S S S W B Expect S W > S B

24 Spiraling Length S w S B FLOW R U

25 Watershed Area % Impervious % Disturbance Width Discharge (Q) Velocity NH4 + SRP Fmed 200 AS/A Chl-a Correlations between uptake metrics and 14 of 34 potential controlling factors Watershed Reach Scale Concentration Transient Storage Metabolism Nutrient Metric NO 3 - S W + + U + V f NH 4 + SRP S W U - V f S W + + U V f Newcomer Johnson et al. (2016) Water

26 S W (NO 3 - uptake length in m) Sw (NO 3 - uptake length in m) S W (SRP uptake in m) S W (SRP uptake length in m) Nitrate & SRP molecules tend to travel further downstream before being assimilated in larger, faster rivers A. Watershed area vs. SRP uptake length 100,000 Watershed area vs. nitrate uptake length Degraded Reference Restored 10,000 1,000 Degraded Reference Restored 10,000 1, R 2 = 0.31 P = R 2 = 0.38* P < 0.001* Watershed area (ha) ,000 10,000 Watershed area (ha) B. Stream width vs. nitrate uptake length 100,000 B. Discharge vs. SRP uptake length ,000 1, R 2 = 0.28 P = R 2 = 0.39* P = 0.002* Stream width (m) Discharge (L/s)

27 U (NH + 4 areal uptake rate in μg/m 2 /s) NH 4+ areal uptake decreases with disturbance Degraded Reference Restored R 2 = Disturbance intensity (%) Newcomer Johnson et al. (2016) Water

28 V f (NH 4 + uptake velocity in mm/min) NH 4+ uptake velocity correlated with land use, transient storage, concentration, and flow A. Disturbance Intensity R 2 = 0.53 Degraded Reference Restored Disturbance intensity (%) C. Median travel time due to transient storage R 2 = % 1% 10% 100% F 200 med (%) B. NH 4+ concentration R 2 = NH 4+ concentration (μg/l) D. Velocity R 2 = Velocity (m/s) E. Relative extent of transient storage R 2 = A S /A F. Discharge R 2 = Discharge (L/s)

29 V I (SRP uptake velocity in mm/min) SRP uptake velocity correlated with flow and concentration Discharge Degraded Reference Restored Chlorophyll-a 1 R 2 = R 2 = Discharge (L/s) SRP Concentration ,000 Ammonium concentration Chl-a (mg/m 2 ) R 2 = R 2 = SRP Concentration (μg/l) NH 4+ Concentration (μg/l)

30 Outline 1 Background 2 Literature Review 3 Nutrient Spiraling 4 Conclusions

31 . And promote nutrient retention Conclusions 1. Stream restoration can be a valuable strategy for reducing nutrient pollution 2. The size of the restoration, hydrologic connectivity, and residence time can be key drivers of nutrient retention 3. Multiple typologies can hydrologically reconnect floodplains & promote retention

32 . And promote nutrient retention Future Directions 1. Restoration and monitoring of buried streams 2. Greater examination of the effectiveness of restoration projects during large storms 3. Examining the effectiveness of stream restoration as projects age over time