Partitioning phosphorus concentrations and loads in tributaries of a recovering urban lake

Figures & data

Figure 1 Onondaga Lake, selected tributaries and long-term monitoring sites.

Figure 2 Time series for two sites on Onondaga Creek that bracket the urban portion of the watershed: (a) Q, with mean daily flow from long-term record for downstream site, (b) TP, (c) TDP, and (d) SRP.

Figure 3 Patterns of dissolved forms of P in Onondaga Creek for dry weather/low flow (< 2.8 m³/s) conditions: (a) distributions of TDP at the upstream and downstream sites during the June–October interval of 2007, (b) distributions of SRP at the upstream and downstream sites during the June–October interval of 2007, and (c) time series of the annual average SRP at the two sites with vertical bars that correspond to ± one standard deviation.

Figure 4 Time series for a runoff event in July of 2007: (a) Q, (b), TDP, (c) TDP_L, (d) PP, and (e) PP_L.

Figure 5 Ratios of estimates of Onondaga Creek CSO loading for TP (TP_L/CSO) and SRP (SRP_L/CSO) and volume (V_CSO) for different years or intervals: (a) TP_L/CSO:V_CSO, and (b) SRP_L/CSO:V_CSO.

Table 1 CSOs on an annual and summertime (May–Sep) basis for the 1995–2007 period: number of events, and estimates of V_CSO, TDP_L/CSO and PP_L/CSO.

	No. Events (#)		V CSO (10^6 m^3)		TDP L/CSO (kg)		PP L/CSO (kg)
	Annual	May–Sep	Annual	May–Sep	Annual	May–Sep	Annual	May–Sep
1995	31	13	1.52	0.92	376	161	830	355
1996	45	27	1.85	1.13	323	198	713	437
1997	31	19	1.00	0.61	174	106	384	234
1998	44	28	1.36	1.01	237	177	525	391
1999	25	13	1.04	0.50	181	88	400	195
2000	40	29	2.23	1.84	389	321	859	710
interval average	36	22	1.50	1.00	280 (0.34) ^+	175 (0.47)	619 (0.34)	387 (0.47)
2001	36	22	1.80	1.25	314	219	693	483
2002	35	22	2.15	1.72	374	300	828	663
2003	46	29	1.83	1.32	320	230	707	509
2004	56	39	2.62	2.22	458	387	1012	854
2005	34	20	1.48	0.92	258	160	570	354
2006	63	36	2.33	1.56	406	252	898	602
2007	46	25	1.78	1.12	311	196	687	433
interval average	45	28	2.00	1.44	349 (0.19)	252 (0.30)	771 (0.19)	557 (0.30)
overall average	41	25	1.77	1.24	317 (0.27)	217 (0.39)	701 (0.27)	479 (0.39)

Figure 6 Particulate P loading from Onondaga Creek for the May–September intervals of 1995–2007: (a) distribution of the ratio of the upstream load to the downstream load and (b) dependence of this ratio on mean flow for the interval.

Figure 7 Closure analysis for sources of P loading to Onondaga Creek for the 2001–2007 interval: (a) TDP_L, and (b) PP_L.

Figure 8 Distribution of ratios of forms of P for Onondaga Lake tributaries for the May–September interval: (a) TDP:TP, upstream site on Onondaga Creek, (b) TDP:TP, downstream site on Onondaga Creek, low flow conditions, (c) TDP:TP, downstream site on Onondaga Creek, high flow conditions, (d) TDP:TP, mouth of Ninemile Creek, (e) TDP:TP, mouth of Ley Creek, (f) SRP:TDP, upstream site on Onondaga Creek, (g) SRP:TDP, downstream site on Onondaga Creek, low flow conditions, (h) SRP:TDP, downstream site on Onondaga Creek, high flow conditions, (i) SRP:TDP, mouth of Ninemile Creek, and (j) SRP:TDP, mouth of Ley Creek.

Table 2 Average flow and phosphorus loading rates to Onondaga Lake.

				Average P Loading Rate (kg/d) (cv ^x )
Source	Period**	Annual/Summer ^xx	Average Flow (m^3/s) (cv)	TP L	PP L	TDP L
Onondaga Creek	1*	A	4.4 (0.26)	26.9 (0.39)	20.4 (0.41)	6.5 (0.31)
	2 ^+	A	5.7 (0.14)	34.9 (0.25)	29.1 (0.27)	5.8 (0.15)
	1	S	2.8 (0.51)	16.3 (0.30)	11.8 (0.32)	4.5 (0.25)
	2	S	3.7 (0.36)	20.3 (0.22)	15.8 (0.24)	4.5 (0.15)
Ninemile Creek	1	A	3.9 (0.30)	18.7 (0.45)	14.5 (0.44)	4.1 (0.46)
	2	A	5.1 (0.17)	21.3 (0.20)	16.3 (0.19)	5.1 (0.22)
	1	S	2.6 (0.48)	11.7 (0.63)	9.2 (0.62)	2.5 (0.68)
	2	S	3.4 (0.33)	12.0 (0.41)	9.2 (0.40)	2.8 (0.42)
Ley Creek	1	A	1.1 (0.22)	9.7 (0.62)	7.1 (0.62)	2.6 (0.62)
	2	A	1.4 (0.11)	10.4 (0.16)	7.8 (0.17)	2.5 (0.14)
	1	S	0.7 (0.38)	5.4 (0.37)	4.0 (0.35)	1.4 (0.42)
	2	S	0.9 (0.36)	6.9 (0.47)	5.2 (0.48)	1.6 (0.43)
Metro (0.55 mg/L)	2	A	2.9	137.5 (0.06)	—	—
		S	2.6	122.5 (0.13)	—	—
Metro (0.12 mg/L)	2	A	2.9	30.0 (0.06)	—	—
		S	2.6	26.7 (0.13)	—	—
Metro (0.02 mg/L)	2	A	2.9	5.0 (0.06)	—	—
		S	2.6	4.5 (0.13)	—	—

Figure 9 Evaluation of TDP vs. stream flow (Q) relationships for the downstream site on Onondaga Creek for two stream flow strata and two time intervals, 1995–2000 (interval 1) and 2001–2007 (interval 2).

Figure 10 Contributions to P loading, Metro and tributaries: (a) case 1, TP_L on an annual basis, TP_Metro = 120 μg/L; (b) case 2, TP_L for the May-September interval, TP_Metro = 120 μg/L; (c) case 3, PP_L adjusted for bioavailability, TP_Metro = 120 μg/L; (d) case 4, effective (available to support primary production) P loading from tributaries, TP_Metro = 120 μg/L; and (e) case 5, effective P loading from tributaries and Metro bypass, TP_Metro = 20 μg/L, estimated manageable fraction of tributary loads indicated. Adjustments for effective P loading as described by Effler et al. (2002). Metro bypass included within TP_Metro/L for all cases. Total loading rates for each case appear below the respective pie charts.

Figure 11 Evaluation of the dependence of TP_epi on summer average external loads of P, 1995–2007: (a) TP_Metro/L, (b) summation of TP_Metro/L and TDP_L, and (c) summation of TP_Metro/L, TDP_L, and PP_L.

Effler , S. W. , O'Donnell , S. M. , Matthews , D. A. , Matthews , C. M. , O'Donnell , D. M. , Auer , M. T. and Owens , E. M. 2002 . Limnological and loading information and a phosphorus total maximum daily load analysis for Onondaga Lake . Lake Reserv Manage , 18 : 87 – 108 .

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