Table 15. Extreme values over the entire period of record for selected parameters, from Paradox data set.

Parameter	Value	Station	Date	Remarks
River Flow
Des Moines River	102,000 ft^3/s	7	13Jul93	flood event
	65,000 ft^3/s	1	09Jun08	flood event
	13 ft^3/s	5	25Jan77	drought conditions
Raccoon River	31,500 ft^3/s	10	19Jun90	flood event
	30,200 ft^3/s	10	13Jul93	flood event
	53 ft^3/s	10	12Jan68	drought conditions
Elevation
Saylorville Lake	891.78 ft NGVD	4S	13Jul93	high flow
	888.59 ft NGVD	4S	11Jun91	high flow
	832.61 ft NGVD	4S	17Jan79	low flow
Lake Red Rock	782.63 ft NGVD	8S	13Jul93	high flow
	779.60 ft NGVD	8S	26Jun84	high flow
	720.00 ft NGVD	8S	08Feb77	drought conditions
Secchi Disc Depth
Saylorville Lake	2.85 m	4S	24May10	data available since 1980
	0.10 m	4S	28Apr87
Lake Red Rock	4.80 m	8S	21Jun84	data available since 1980
	0.06 m	8S	19Jun90
Transparency tube depth	>120 cm 1.5 cm 1.3 cm	several 7 10	periodically 09Mar10 25May04	parameter began 2001 ice melt significant rainfall
Water temperature	38.0°C (100.4°F)	6	24Aug71	thermal pollution
	-0.4°C (31.6°F)	7 & 10	10Feb97 & 11Jan00	severe cold
Specific Conductance	1,926 μs/cm 1,827 μs/cm 236 μs/cm 119 μs/cm	WBC-I^a 1 10 7	20Aug79 18Jan77 19Mar79 09Mar10	Drought conditions High flow Ice Melt

When two or more values are listed for a maximum or minimum, it means the value and the next highest or lowest unrelated value, or else it lists values attributed to different mechanisms (i.e., point source versus nonpoint source) or ecosystems (i.e., river versus reservoir).

^aDiscontinued parameter or station.

Table 15. Continued.

Parameter	Value	Station	Date	Remarks
pH	9.90	1	11Dec69	–
	6.00	2^a	12Feb71	Station 2 was near Madrid
Carbon dioxide	94.0 mg/l	4B	24Jul84	–
	0.0 mg/l	several	periodically	when pH > 8.30
Phenolphthalein alkalinity	59 mg/l	4-RIVER^a	11Dec69	Station 4-RIVER was near
				Polk City
	0 mg/l	several	often	when pH < 8.30
Total alkalinity	589 mg/l as CaCO3	1	18Jan77	low flow
	67 mg/l as CaCO3	7	07Jul87	high flow
Dissolved oxygen	50.08 mg/l	8S	20Jan76	376% of saturation (reservoir)
	28.90 mg/l	5	23Feb68	203% of saturation (river)
	0.65 mg/l	0	25Jan77	4.6% of saturation (river)
	0.00 mg/l	4B	30Jul79	0% of saturation (reservoir)
Calcium hardness	493 mg/l as CaCO3	5	02Jan85	low flow (winter)
	58 mg/l as CaCO3	1	25Jul89	intense productivity
Total hardness	766 mg/l as CaCO3	5	02Jan85	low flow (winter)
	108 mg/l as CaCO3	9	30Aug77	high flow
Total organic carbon	341 mg/l <1 mg/l	10 several	02Jun80 periodically	low flow –
Specific conductance^a	1,827 µmhos/cm	1	18Jan77	low flow
	236 µmhos/cm	10	19Mar79	high flow
Inorganic carbon^a	148 mg/l	1	18Jan77	low flow
	13 mg/l	several	periodically	high flow
Suspended solids	12,490 mg/l	10	30May89	high flow (Raccoon River)
	10,200 mg/l	7	06Jul82	high flow (Des Moines River)
	<1 mg/l	several	a few	low flow (winter)

Table 15. Continued.

Parameter	Value	Station	Date	Remarks
Turbidity	20,000 NTU	10	15Jun82	high flow (Raccoon River)
	6,400 NTU	7	06Jul82	high flow (Des Moines River)
	1 NTU	several	a few	ice cover; high elevation
BOD	32.0 mg/l	6	23Feb77	low flow (waste)
	30.2 mg/l	5	03May68	low flow (plankton)
	<0.1 mg/l	several	periodically	under ice cover
COD^a	553 mg/l	10	16May74	high flow
	0.0 mg/l	5	14Feb69	low flow
Organic nitrogen	13.0 mg/l	4	12Sep68	–
	<0.01 mg/l	several	periodically	–
Ammonia nitrogen	22.4 mg/l	6	08Feb77	low flow (waste)
	11.9 mg/l	1	01Feb77	low flow (waste)
	4.17 mg/l	6	16Jan90	low flow
	3.65 mg/l	4B	23Jul96	stratification
	<0.01 mg/l	several	periodically	algal utilization
NO2 (as N)^a	0.62 mg/l	3-RIVER^a	16Oct68	data from 1967–1976 only
	<0.01 mg/l	many	often	–
NO2 + NO3 (as N)	18.2 mg/l 18.1 mg/l	10 1	18Jun02 12Jun90	flow increase (Raccoon River) high flow (Des Moines River)
	<0.01 mg/l	several	periodically	low flow, algal utilization
Un-ionized ammonia (as N)	1.06 mg/l 0.742 mg/l	1 6	29Mar68 25Jan77	low flow, high pH low flow
	0.200 mg/l	8B	16Mar81	stratification
	<0.001 mg/l	several	periodically	high flow, low pH
Total nitrogen (as N)	27.9 mg/l 17.2 mg/l 0.20 mg/l	6 10 10	08Feb77 26Jun01 16May01	low flow (waste)

Table 15. Continued.

Parameter	Value	Station	Date	Remarks
Orthophosphate	14.7 mg/l	6	08Feb77	low flow (waste)
	<0.03 mg/l	several	periodically	algal utilization
Total phosphate	17.3 mg/l	6	08Feb77	low flow (waste)
	13.2 mg/l	10	19Mar79	high flow (runoff)
	<0.03 mg/l	several	periodically	low flow
Dissolved silica (as SiO2)	59.6 mg/l 50.7 mg/l	9 5	23Aug72 05Jul68	diatom growth storm event
	<0.01 mg/l	several	periodically	algal utilization
Soluble arsenic^a	8.3 µg/l	5	10Jul90	–
	LTDL^b	many	often	–
Soluble cadmium	6.4 µg/l	5	09Jul91	since May 1988
	LTDL	most	often	method change
Soluble chromium^a	20 µg/l	1	13Jan87	–
	LTDL	many	often	–
Soluble copper	72 µg/l	1	11Oct94	initiated in WY91
	LTDL	a few		–
Soluble lead	22 µg/l	9	05Oct95	since May 1988
	LTDL	most	often	method change
Soluble mercury	2.5 µg/l	10	28Apr82	–
	LTDL	many	often	–
Soluble zinc^a	479 µg/l	9	05Oct95	–
	LTDL	a few		–
Chlorophyll a	880 mg/m^3	1	16Nov67	river
	297 mg/m^3	3B	25Nov80	reservoir
	0 mg/m^3	several	periodically	high flow, turbid

^bLTDL—less than detection limit.

Table 15. Continued.

Parameter	Value	Station	Date	Remarks
Chlorophyll b	354 mg/m^3	4–RIVER^a	05Jan68	–
	90 mg/m^3	7	21Jun88	–
	0 mg/m^3	several	periodically	–
Chlorophyll c	77 mg/m^3 64 mg/m^3	1 4S	24Aug81 28Jan80	river reservoir
	0 mg/m^3	several	periodically	–
Pheophytin a	264 mg/m^3	1	30Mar81	river
	73mg/m^3	3B	22Sep80	reservoir
	0 mg/m^3	several	periodically	–
Fecal coliform bacteria	207,000/100 ml	10	12Sep78	high flow
	200,000/100 ml	6	01Feb77	low flow
	17,000/100 ml	WBB3	23Sep86	beach
	>12,000/100 ml	3B	08Nov77	reservoir
	<1/100 ml	several	periodically	in the reservoirs
Escherichia coli bacteria	16,700/100 ml 4,700/100 ml	10 SPB	15Jun04 18Aug04	began 2001 beach
Total gas saturation^c	132% 88.2% 135%	8S 8S 9	13Aug91 09Jun88 23Jun08	St. 8S began 1988 – St. 9 began 1983
	98.5%	5	11Jan00	St. 5 began 1989
Nitrogen gas saturation^c	136% 61.8% 156%	9 8S 9	04Sep07 25July00 06Jun95	St. 8S began 1988 St. 9 began 1983
	98%	5	12Jul10	St. 5 began 1989

^cfrom Stations 5, 8S and 9 only.

Table 15. Continued.

Parameter	Value	Station	Date	Remarks
TSI (chlorophyll)	31 37 86 88	8S 4S/8S 8S 4S	13Feb79/14Jun10 06Jun89/09Jun08 16May89 17Mar97	ice cover – – –
TSI (phosphorus)	31 53 93 114	4S 8S 4S 8S	27Mar02 27Jul99 10Mar80 14Dec76	– – – –
TSI (Secchi)	37 46 93 101	8S 4S 4S 8S	21Jun83 21May07 28Apr87 19Jun90	high reservoir pool high reservoir pool – –
Water quality index^c	30	7	01Nov83	high suspended solids
	94	4S & 6	27Mar02	–