Effect of a moderate-size reservoir on transport of trace elements in a watershed

Figures & data

Figure 1. Location of Grand Lake in Oklahoma and the United States. Arrows indicate direction of water flow from major tributaries the Neosho River (NR), the Spring River (SR), and the Elk River (ER) and minor tributaries Tar Creek (TC), Buffalo Creek (BC), and Honey Creek (HC) through the reservoir and into the Grand River (GR). Circles indicate locations where water and suspended sediment samples were collected, although samples were not collected at all locations on all sampling excursions. Gray-black shading indicates relative depth between the shoreline and the dam face, where water is usually 36 m deep. Map adapted from OWRB (2009).

Figure 2. Distribution of trace element concentrations in filtered water samples. Data are depicted along several one-dimensional number lines sorted by sampling location and excursion. Circles denote samples collected upstream of Grand Lake in tributaries. Diamonds denote samples collected <8 m deep in the water column (the bottom of the summertime surface mixed layer). Triangles denote samples collected ≥8 m deep. Squares denote samples collected downstream of Pensacola Dam. Symbols appear at the median values of each subset of data, and error bars extend to the 5^th and 95^th percentiles of each subset of data. The numbers above the panel showing iron (Fe) concentrations indicate the number (n) of observations in each subset of samples, and these apply to the corresponding number lines for all panels other than Fe. Labels at the bottom of each panel identify sampling excursions.

Figure 3. Distribution of trace element concentrations in suspended sediment samples. Because the detection limit varied between samples, only the approximate maximum detection limit is denoted where appropriate. Other details are as in Figure 2.

Table 1. Water flux (GL/day) and mass flux of elements in (Table 1A) filtered samples (kg/d) and (Table 1B) suspended sediment samples (kg/d).

Table 1A
Excursion	Water^a	Fe	Mn	Pb	Zn	Cd	As	P	DL^b
Summed loading of all tributaries
Dec	3.1	52	54	BDL	230	0.39	2.1	250	0.31
Feb–Mar	58	4400	1700	8.2	1600	BDL	66	14,000	5.8
May	16	320	290	BDL	520	BDL	62	1600	1.6
Aug	2.4	8.7	12	BDL	6.3	BDL	4.4	90	0.24
Nov	2.2	3.1	2.3	BDL	5.2	BDL	0.16	12	0.019
Export via Pensacola Dam
Dec	3.0	BDL	17	BDL	3.3	BDL	3.7	240
Feb–Mar	18	200	120	BDL	13	BDL	25	3800
May	32	1100	165	1.6	120	1.6	30	3800
Aug	11	5.4	1000	0.54	14	0.54	9.3	320
Nov	8.3	130	180	0.42	9.2	0.42	8.4	4.1
Net flux through Grand Lake^c
Dec	0.12	50	36	BDL	220	0.39	−1.6	5.4
Feb–Mar	40	4200	1600	7.3	1600	BDL	41	11,000
May	−16	−800	130	−0.81	400	−0.81	32	−2200
Aug	−8.4	3.3	−990	−0.42	−7.8	−0.42	−4.9	−230
Nov	−6.1	−130	−180	−0.41	−4.0	−0.41	−8.2	8.1
Table 1B
Excursion	Water^a	Fe	Mn	Pb	Zn	Cd	As	P	DL^b
Summed loading of all tributaries
Dec	3.1	1200	150	1.3	240	0.23	1.1	200	0.024
Feb–Mar	58	190,000	1900	770	21,000	43	16,000	11,000	1.1
May	16	8900	450	33	1500	3.2	2.3	620	0.092
Aug	2.4	560	110	2.2	47	0.20	0.25	42	0.0096
Nov	2.2	160	11	0.50	9.3	0.047	0.065	11	0.002
Export via Pensacola Dam
Dec	3.0	310	8	1.7	120	0.40	0.94	71
Feb–Mar	18	13,000	790	13	500	0.18	600	530
May	32	28,000	1000	45	720	1.0	8.8	1900
Aug	11	1600	120	1.6	30	BDL	0.62	120
Nov	8.3	1500	540	1.9	25	0.13	1.5	140
Net flux through Grand Lake^c
Dec	0.12	860	140	−0.37	120	−0.16	0.12	130
Feb–Mar	40	180,000	1100	753	20,000	43	15,000	10,000
May	−16	−19,000	−590	−12	790	2.1	−6.4	−1200
Aug	−8.4	−1100	−6.7	0.57	17	0.17	−0.37	−77
Nov	−6.1	−1300	−530	−1.4	−16	−0.082	−1.4	−130

^aNet water flow through Grand Lake taken from Wildman (2016).

^bDetection limit for Mn, Pb, Zn, Cd, and As; for Fe and P, DL is 10 times higher than the value shown; DL applies to both loading and export values.

^cLoading via tributaries minus export out the dam was calculated before rounding to the appropriate number of significant figures.

Figure 4. Biplot of principal component analysis of elemental concentrations in filtered samples. Loadings are depicted as open double circles and correspond to upper and right-hand axes. Scores are other symbols and correspond to lower and left-hand axes. Scores are represented as: (filled diamonds) upstream samples from February-March and May (i.e., months of high flow); (open diamonds) other upstream samples; (filled squares) summertime surface mixed layer; (open squares) other lake samples from <8 m deep; (filled triangles) summertime metalimnion and bottom water; (open triangles) other lake samples from ≥8 m deep; and (filled circles) downstream samples. PC1 and PC2 described 38% and 21% of the variance in the dataset, respectively.

Figure 5. Plot of logistic function relating occurrence of detectable Cd_f to logarithm of Zn_f concentration by showing observed values (open diamonds, left vertical axis), the percentage of Cd observations that exceeded the detection limit for a given 0.5-log-unit window on the horizontal axis (gray circles, right vertical axis), and the logistic function fitting the observed data (dotted line, left vertical axis).

[OWRB] Oklahoma Water Resources Board. 2009. Hydrographic survey of Grand Lake. Oklahoma City (OK).

 Google Scholar

Wildman RA. 2016. Mercury and methylmercury in a reservoir during seasonal variation in hydrology and circulation. Lake Reserv Manage. 32:89–100.

 Web of Science ®Google Scholar