URBAN NON-POINT SOURCE IMPACTS ON SEATTLE AREA STREAM PHOSPHORUS TRANSPORT

Transcription

1 URBAN NON-POINT SOURCE IMPACTS ON SEATTLE AREA STREAM PHOSPHORUS TRANSPORT Michael T. Brett, Sara E. Stanley, Benjamin O. Brattebo, Micaela Ellison & Giorgios Arhonditsis Department of Civil & Environmental Engineering, Box 3527, University of Washington, Seattle, WA

2 How much does phosphorus transport differ in Seattle area urban and forest streams? SCALES: Long term (decadal), seasonal (monthly), inter-annual (daily), and event based (hourly).

3 Lake Washington in the Past (and the Future?) Eutrophication & Surface WQ World Watch Magazine

4 Land Cover

5 Land Cover Versus Stream Nutrients: Normal Flows Geomean TP (µg/l) 8 Total Phosphorus r 2 = % 2%4%6%8%% Geomean NO 3 (µg/l) Nitrate 15 r 2 = % 2%4%6%8%% Geomean turbidity (NTUs) Turbidity 6 r 2 =.33 5 Tibbets % 2%4% 6%8%% Percent Urban Land Cover Percent Urban Land Cover Percent Urban Land Cover Geomean SRP (µg/l) Soluble Reactive Phosphorus 5 r 2 = Geomean NH 4 (µg/l) Ammonium r 2 =.36 Tibbets Geomean TSS (mg/l) Total suspended solids r 2 =.3 % 2%4%6%8%% % 2%4%6%8%% % 2%4%6%8%% Percent Urban Land Cover Percent Urban Land Cover Percent Urban Land Cover

6 Seasonal Fluctuations in Stream Constituent Concentrations Total & Soluble Reactive Phosphorus 2. Nitrate & Ammonium 1. NO3 NH4 Summer seasonal mean/yearly mean TP SRP 1. TSS and Turbidity 1. TSS Summer Fall Winter Spring Summer Fall Winter Spring Summer Summer Fall Winter Spring Summer seasonal mean/yearly mean Turbidity seasonal mean/yearly mean SRP:DIN ratio Summer 48 Winter 133

7 Percent Urban Enrichment Average Average Percent Constituent Units Forested Urban Enrichment Total Phosphorus µg/l % Soluble Reactive P µg/l % Total Nitrogen µg/l % Nitrate µg/l % Ammonium µg/l % Turbidity NTUs % Total Susp. Solids mg/l %

8 Phosphorus concentration (µg/l) TP SRP Seattle For. Seattle Urb. Omernik For. Omernik Ag. Seattle forest streams have 15% more DIN than typical forest streams Seattle urban streams have about 5% as much phosphorus as typical agricultural streams Nitrogen concentration (µg/l) TN DIN Seattle urban streams have about 35% as much nitrogen as typical agricultural streams Seattle For. Seattle Urb. Omernik For. Omernik Ag.

9 Averaged Change in SRP Concentrations for the most urban Seattle area streams (Thornton, Juanita, McAleer, Lyon, Forbes, Kelsey) Urban stream SRP concentrations Mean Annual SRP conc. (µg/l) y = -.86x r 2 = Mean annual nitrate conc. (µg/l) Urban stream nitrate concentrations 9 8 y = -9x r 2 = % decline in SRP 15% decline in NO 3 WHY: BMPs, human behavior, catchment surface disturbance?

10 An Annual Time Series of Stream Phosphorus Transport Issaquah - Forest North - Mixed Swamp - Mixed Thornton - Urban Daily TP Weekly SRP Daily TSS

11 Objective: to collect a high resolution stream phosphorus concentration database in order to develop statistical time series models of stream phosphorus transport. Model structure: Seasonal term Spikeness term Antecedent term Rainfall term

12 Overall TP varied by ± 5% from week to week Phosphorus (µg/l) North Creek TP SRP A S O N D J F M A M J J A 21/2 SRP varied by ± 2% from week to week SRP was on average 48% of TP

13 Soluble Reactive P (µg*l -1 ) Issaquah Creek Observed North Creek r 2 =.25 Soluble reactive phosphorus times series Predicted r 2 =.85 Soluble Reactive (µg*l-1 P ) Swamp Creek r 2 =.79 A S O N D J F M A M J J A 21/2 Thornton Creek r 2 =.63 A S O N D J F M A M J J A 21/2

14 Total phosphorus times series Total Phosphorus (µg*l -1 ) Issaquah Creek r 2 =.49 Observed Predicted North Creek r 2 =.55 Total Phosphorus (µg*l-1) Swamp Creek r 2 =.53 Thornton Creek r 2 =.38 A S O N D J F M A M J J A 21/2 A S O N D J F M A M J J A 21/2

15 Phosphorus transport during storm events over a range of land use conditions

16 Study sites Four watersheds Agriculture, 392 ha Urban, 123 ha Forested, 497 ha Suburban, 197 ha All sampling sites were within Green-Duwamish River watershed

17 Forested Stream Flow (L/s) Time (hrs)

18 2 Forested Stream 35 Flow (L/s) TSS (mg/l) Time (hrs)

19 2 Forested Stream 35 Flow (L/s) TSS (mg/l) Tot. P (µg/l) Time (hrs)

20 2 175 Forested Stream 35 3 Flow (L/s) Tot. P (µg/l) Tot. Diss. P (µg/l) Time (hrs)

21 2 175 Forested Stream 35 3 Flow (L/s) Tot. Diss. P (µg/l) Cond. (µs/cm) Time (hrs)

22 Urban Stream 25 Flow (L/s) Time (hrs)

23 Urban Stream Flow (L/s) TSS (mg/l) Time (hrs)

24 Urban Stream Flow (L/s) TSS (mg/l) Tot. P (µg/l) Time (hrs)

25 Urban Stream Flow (L/s) Tot. P (µg/l) Tot. Diss. P (µg/l) Time (hrs)

26 Urban Stream Flow (L/s) Tot. Diss. P (µg/l) Cond. (µs/cm) Time (hrs)

27 Agricultural Stream Flow (L/s) Time (hrs)

28 Agricultural Stream 3 25 Flow (L/s) TSS (mg/l) Time (hrs)

29 Agricultural Stream 3 25 Flow (L/s) TSS (mg/l) 8 2 Tot. P (µg/l) Time (hrs)

30 8 Agricultural Stream Flow (L/s) Tot. P (µg/l) Tot. Diss. P (µg/l) Time (hrs)

31 Agricultural Stream 3 25 Flow (L/s) Tot. Diss. P (µg/l) 8 2 Cond. (µs/cm) Time (hrs)

32 Agricultural Stream 3 25 Flow (L/s) TSS (mg/l) Tot. P (µg/l) Tot. Diss. P (µg/l) Cond. (µs/cm) Time (hrs)

33 Summary: It is easy to characterize the between and within stream TDP dynamics

34 Summary: It is easy to characterize the between and within stream TDP dynamics It is generally agreed that TDP is nearly % bioavailable

35 Summary: It is easy to characterize the between and within stream TDP dynamics It is generally agreed that TDP is nearly % bioavailable Variation in stream particulate P concentrations is very difficult to predict

36 Summary: It is easy to characterize the between and within stream TDP dynamics It is generally agreed that TDP is nearly % bioavailable Variation in stream particulate P concentrations is very difficult to predict The bioavailability of PP has been previously reported to vary from <1% to >8%

37 Summary: It is easy to characterize the between and within stream TDP dynamics It is generally agreed that TDP is nearly % bioavailable Variation in stream particulate P concentrations is very difficult to predict The bioavailability of PP has been previously reported to vary from <1% to >8% THEREFORE:

38 We need to know how the bioavailability of the PP fraction varies with land use and flow conditions in Seattle Area streams!

39 We need to know how the bioavailability of the PP fraction varies with land use and flow conditions in Seattle Area streams! See Micaela Ellison s poster

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41 2 Forested Stream 35 Flow (L/s) TSS (mg/l) Tot. P (µg/l) Tot. Diss. P (µg/l) Cond. (µs/cm) Time (hrs)

42 Urban Stream Flow (L/s) TSS (mg/l) Tot. P (µg/l) Tot. Diss. P (µg/l) Cond. (µs/cm) Time (hrs)

43 Agricultural Stream 3 25 Flow (L/s) TSS (mg/l) Tot. P (µg/l) Tot. Diss. P (µg/l) Cond. (µs/cm) Time (hrs)