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DO depletion-excerpts from leading literature

S.M. Mandaville Post-Grad Dips., Soil & Water Conservation Society of Metro Halifax (SWCSMH)

Dated: March 27, 2019

Contents:

Formal definition of trophic status (cautionary notes)
Oxygen deficits

Calculation of stratum areas/volumes
Solubility of oxygen from an atmosphere containing 20.9 percent oxygen by volume

The Corvallis LEI (Lake Evaluation Index) ........ an innovative composite index

Formal definition of trophic status

For establishing trophic status reliably, access our web page on the Formal definition of trophic status.

Several variables have to be taken into account in addition to DO depletion. Access the aforesaid web page for extensive scientific rationale.

Oxygen deficits

Excerpts from Mackie, G.L. 2004. Applied Aquatic Ecosystem Concepts. Second Ed. Kendall/Hunt Publishing Company. 784 pp. ISBN 0-7575-0883-9.

The oxygen deficit in a lake is the amount of oxygen required to reach the saturation level. All calculations must account for the atmospheric pressure at the surface of the lake by using correction factors.

The most meaningful oxygen deficit measurement is the relative hypolimnial oxygen deficit because it accounts for oxygen deficits in layers below the hypolimnetic surface.

Essentially, one measures the dissolved oxygen contents of several vertical columns of water at the beginning and at the end of the stratification period. Each column has a cross-sectional area of 1 cm². The height (depth) of a column is usually 1 to 2 m. The difference in oxygen content for each layer (column) between the beginning and the end of the stratified period is summed to give a relative areal hypolimnial oxygen deficit, or RAHOD.

Oligotrophic lakes have RAHOD values of <0.017 mg O₂ lost cm^-² day^-¹, and eutrophic lakes have >0.033 mg O₂ lost cm^-²day^-¹.

The other two kinds of oxygen deficit are, actual and absolute, depending upon the saturation temperature used in the calculation. The main criticism of actual oxygen deficits is it assumes that the water was saturated at the observed temperature during spring turnover. The absolute oxygen deficit suffers the same criticism as the actual oxygen deficit in that it assumes saturation at 4 ºC, which is not necessarily true.

Calculation of stratum areas/volumes:

Alternately to a planimetre, one can rely on computer technology and use a digitizer for lot higher accuracy. With proper software, one can make areal estimates for any shape accurately and quickly. In this method, a mouse with a pointer is used to trace the outline of the image. The mouse button is pressed several times as the outline is traced. The more often the button is pressed, the more accurate the estimate of the area enclosed, or the length of line being traced. The computer program integrates the data and converts it into area (e.g. lake area) or length of line traced (e.g. shoreline length). Some digitizers can calculate the volumes of each stratum as well.

Solubility of oxygen from an atmosphere containing 20.9 percent oxygen by volume:

Note:

Lakes at high elevations (where there is less oxygen per unit volume of air) contain less dissolved gas per unit volume than do lakes with the same temperature at sea level.

Temp.	Oxygen from normal atmosphere	Correction factors for oxygen saturation at various altitudes
^oC	mg per L	Altitude	Pressure
^oC	mg per L	m	mm	Factor
0	14.62	0	760	1.00
1	14.23	100	750	1.01
2	13.84	200	741	1.03
3	13.48	300	732	1.04
4	13.13	400	723	1.05
5	12.80	500	714	1.06

6	12.48	600	705	1.08
7	12.17	700	696	1.09
8	11.87	800	687	1.11
9	11.59	900	679	1.12
10	11.33	1000	671	1.13

11	11.08	1100	663	1.15
12	10.83	1200	655	1.16
13	10.60	1300	647	1.17
14	10.37	1400	639	1.19
15	10.15	1500	631	1.20

16	9.95	1600	623	1.22
17	9.74	1700	615	1.24
18	9.54	1800	608	1.25
19	9.35	1900	601	1.26
20	9.17	2000	594	1.28

21	8.99	2100	587	1.30
22	8.83	2200	580	1.31
23	8.68	2300	573	1.33
24	8.53	2400	566	1.34
25	8.38	2500	560	1.36

26	8.22
27	8.07
28	7.92
29	7.77
30	7.63

The Corvallis LEI (Lake Evaluation Index)

References:

Porcella, D.B., Petersen, S.A., and Larsen, D.P. 1979. Proposed method for evaluating the effects of restoring lakes. Pages 265–310 in Limnological and Socioeconomical Evaluation of Lake Restoration Projects: Approaches and Preliminary Results. EPA 600/3-79-005. U.S. Environ. Prot. Agency, Washington, DC. vii, 330 p.
Also cited in Holdren, C., Jones, W., and Taggart, J. 2001. Managing Lakes and Reservoirs. N. Am. Lake Manage. Soc. and Terrene Inst., in coop. with Off. Water Assess. Watershed Prot. Div. U.S. Environ. Prot. Agency, Madison, WI. xiv, 382 pp.

The superb LEI proposed by Porcella et al (1979) is a rare composite trophic state index that includes Total Phosphorus (TP), Total Nitrogen (TN), Chlorophylla (Cha), Secchi Disk (SD), macrophyte coverage, and dissolved oxygen values in lakes.

Download the full document in PDF (https://1drv.ms/b/s!Au0xeIA-MCofg3ShH_HmNC5EW7Oe)

Excerpts from Porcella et al:

Below, the scan inserts are only for DO:

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