Spatiotemporal patterns of baseflow metrics for basins draining the Oak Ridges Moraine, southern Ontario, Canada

Figures & data

Figure 1. Basins draining the Oak Ridges Moraine (ORM) with streamflow records from the Water Survey of Canada, the ORM management boundary and the extent of outcropping glaciofluvial deposits (OGS 2003). Cross-sections presented in Figure 2 are indicated.

Figure 2. Geologic cross-sections of the Oak Ridges Moraine (ORM) and areas to the north and south. Geology for cross-sections B–B’ and C–C’ described in Earthfx Inc. (2013).

Figure 3. Percentage of basin area consisting of outcropping glaciofluvial deposits vs. (a) basin area and (b) mean basin slope.

Figure 4. Areas classed as (a) urban, (b) forest and (c) open water plus wetland in basins draining the Oak Ridges Moraine (ORM) based on the Southern Ontario Land Resource Information System (SOLRIS) for the period 2000–2002. The Water Survey of Canada (WSC) station codes for basins discussed in the text are indicated.

Table 1. Summary of climatic, runoff and baseflow metrics across all years of record and all basins.

Metric	Mean	SD	CV	Maximum	Minimum
P (mm)	866	68	0.08	1259	552
PET (mm)^a	545	17	0.03	790	458
P – PET (mm)^a	346	160	0.46	799	24
R (mm)	336	105	0.31	742	60
CV R	0.23	0.09	0.39	0.49	0.07
BF (mm)	235	98	0.42	524	27
CV BF	0.19	0.07	0.37	0.36	0.06
BF/P	0.27	0.10	0.37	0.59	0.04
CV BF/P	0.18	0.05	0.28	0.31	0.03
BFI	0.67	0.11	0.16	0.93	0.31
CV BFI	0.07	0.03	0.43	0.14	0.02

CV: coefficient of variation; SD: standard deviation; P: precipitation; PET: potential evapotranspiration; R: runoff; BF: baseflow; BF/P: baseflow/precipitation; BFI: baseflow index.

^a Could only be determined up to 2006.

Table 2. Best-fit multiple regression relationships for baseflow metrics. Regression coefficients are significant at p = 0.001 for bolded independent variables, at p = 0.01 for italicized variables and at p = 0.05 for underlined variables. n = number of basins used in multiple regression analysis. BF: baseflow; BF/P: baseflow/precipitation; BFI: baseflow index; CV: coefficient of variation; PC: principal component.

(a) All WYs, best-fit relationships
Metric	Equation	Adjusted R^2	n	Significance level of regression model
BF (mm)	Y = 2235+ 64*PC1 – 28*PC2	0.49	60	< 0.001
CV BF	Y = 0.19 – 0.05*PC1 + 0.02PC2	0.48	56	< 0.001
BF/P	Y = 0.27 + 0.06*PC1 – 0.03*PC2	0.42	60	< 0.001
CV BF/P	Y = 0.18 – 0.02*PC1	0.11	56	< 0.01
BFI	Y = 0.67 + 0.09*PC1	0.68	60	< 0.001
CV BFI	Y = 0.07 – 0.02*PC1 + 0.01*PC2 + 0.01PC3	0.49	56	< 0.001
(b) WYs 1975–1984, best-fit relationships
Metric	Equation	Adjusted R^2	n	Significance level of regression model
BF (mm)	Y = 238 + 57*PC1	0.34	26	< 0.001
CV BF	Y = 0.16 – 0.06*PC1	0.55	26	< 0.001
BF/P	Y = 0.27 + 0.06*PC1	0.34	26	< 0.001
CV BF/P	Y = 0.17 – 0.05*PC1	0.48	26	< 0.001
BFI	Y = 0.67 + 0.08*PC1	0.47	26	< 0.001
CV BFI	Y = 0.05	0.06	26	> 0.1

Figure 6. (a) Basins with significant positive correlations between baseflow (BF) and precipitation (P) in a given water year (WY); (b) basins with significant negative correlations between BFI and P in a given WY. Basins left blank did not have significant correlations or were not analyzed for baseflow due to flow regulation.

Figure 7. Basins with (a) above- and below-average baseflow (BF), and (b) above- and below-average baseflow index (BFI). Basins left blank had BF or BFI values within 1 standard deviation of mean values across all basins or were not analyzed for baseflow due to flow regulation.

Table 3. Thresholds of basin area, % glaciofluvial deposits (GFD), mean basin slope and percentage of forest and urban coverage associated with basins with mean baseflow (BF), and baseflow index (BFI) more than 1 standard deviation above or below the mean across all basins.

	Basin area (km^2)	% GFD	Mean basin slope (%)	% forest	% urban
BF > mean + 1 SD	< 82	None	> 5.1	> 16	< 17
BF < mean – 1 SD	None	< 34	< 5.9	< 20	None
BFI > mean + 1 SD	< 76	> 37	> 5.1	> 28	< 17
BFI < mean – 1 SD	< 143 (all but 1 < 56)	< 13	< 4.5	< 15	None

Table 4. Basins with ≥ 10 water years (WYs) of record with statistically significant temporal trends. Values are the slopes of the Kendall–Theil Robust Lines determined for each trend. P: precipitation; BF: baseflow; BF/P: baseflow/precipitation; BFI: baseflow index.

WSC station code; name	Period of record; # of WYs	P(mm y^−1)	BF(mm y^−1)	BF/P(y^−1)	BFI(y^−1)
02ED100; Beeton Cr nr Tottenham	1969–1974, 1976–1986, 1998–2009; 29	3.6	ND		ND
02HD006; Bowmanville Cr at Bowmanville	1960–1994, 2007–2010; 39	4.5	2.1
02HK009; Burnley Cr above Warkworth	1984–1997, 2003–2009; 21			0.0017
02HC023; Cold Cr nr Bolton	1963–1992, 1994–1999; 36		1.5	0.0014
02HC032; East Humber R at King Creek	1966–1974, 1976–1992, 2004–2010; 33	2.8	1.0	0.0008
02HC009; East Humber R at Pine Grove	1954–1974; 1976–2010; 56	2.1	0.8
02HD003; Ganaraska R above Osaca	1960–2010; 51	4.0	1.0		0.0009
02EC009; Holland R at Holland Landing	1966–2010; 45			–0.0008	–0.0024
02HC025; Humber R at Elder Mills	1963–2002, 2004–2006; 43	2.6
02HC012; Humber R nr Cedar Mills	1958–1980; 23		3.3
02HJ001; Jackson Cr at Peterborough	1963–2010; 48	3.2			0.0017
02HC028; Little Rouge Cr nr Locust Hill	1965–2010; 46	3.6	1.0	0.0008
02HC018; Lynde Cr nr Whitby	1962–1972, 1976–2010; 46	3.2	1.2
02HG002; Nonquon R nr Port Perry	1994-10; 17		4.4	0.0037
02HD004; North West Ganaraska R nr Osaca	1960–1990, 2003–2010; 39	5.7	1.5		0.0011
02HD008; Oshawa Cr at Oshawa	1960–1978, 1981–2010; 49	3.5			0.0014
02HC022; Rouge R nr Markham	1963–1991, 1995–2010; 45	2.4	ND		ND
02EC010; Schomberg R nr Schomberg	1967–1988, 1990–1997, 2003–2010; 38	2.9
02HD010; Shelter Valley Br nr Grafton	1966–2010; 45				0.0013
02HD007; Soper Cr at Bowmanville	1960–1967, 1969–1972, 1975–1986; 24	7.8	1.7	0.0019
02EC101; Uxbridge Br at Uxbridge	1971–1980, 1982–1984; 13		4.4
02HC026; West Duffins Cr at Green River	1964–1967, 1971–1987; 21	7.3	3.4	0.0032
02HD009; Wilmot Cr nr Newcastle	1966–1988, 1990–1997, 2003–2010; 39	3.2	1.7	0.0011	0.0009

ND: BF not determined due to flow regulation; bold: significant at p = 0.05 level; otherwise, significant at p = 0.1 level.

Figure 8. Basins with significant temporal trends in (a) precipitation (P), (b) baseflow (BF), (c) baseflow/precipitation (BF/P) and (d) baseflow index (BFI). Basins left blank in (a) did not have significant trends or did not have sufficient data to conduct trend analyses. Basins left blank in (b–d) did not have significant trends, did not have sufficient data to conduct trend analyses or were not analyzed for baseflow due to flow regulation.

Figure 9. Double mass curves for cumulative runoff (R) vs. precipitation (P) for (a) 02EC009 – Holland R at Holland Landing and (b) 02HD008 – Oshawa Cr at Oshawa, and for cumulative baseflow (BF) vs. P for (c) Holland R at Holland Landing and (d) Oshawa Cr at Oshawa.

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