Appendix A. Quality-Assurance Data for Water Samples

Table A1. Blank sample results for the water-quality sample collection program.

[Abbreviations: mg/L, milligram per liter; NA, not applicable]

Analyte	Number of samples		Percentage of blank samples	Minimum reporting level (mg/L)	Number of blank samples greater or less than minimum reporting level	Value of blank samples greater than minimum reporting level (mg/L)
Analyte	Blank	Total	Percentage of blank samples	Minimum reporting level (mg/L)		Maximum	Median
2002
Orthophosphate-P	18	218	8	0.01	10	0.03	0.02
Ammonia-N	18	218	8	.02	18	NA	NA
Nitrate/nitrite-N	18	218	8	.03	18	NA	NA
Total phosphorus	19	114	17	.004	18	.007	NA
Chlorophyll a	1	101	1	NA	NA	2.4	NA
2003
Orthophosphate-P	24	130	18	0.007	20	NA	NA
Ammonia-N	24	130	18	.015	9	0.202	0.032
Nitrate/nitrite-N	24	130	18	.022	17	.038	.032
Total phosphorus	16	81	2	.004	11	.005	NA
Chlorophyll a	2	62	3	NA	NA	0	NA
2004
Orthophosphate-P	21	191	11	0.006	0	NA	NA
Ammonia-N	29	199	15	.01	7	0.188	0.034
Nitrate/nitrite-N	21	191	11	.016	17	.037	.022
Total phosphorus	22	133	17	.004	17	NA	NA
Chlorophyll a	0	106	0	NA	NA	NA	NA

Table A2. Split sample results for the water-quality sample collection program, 2002–04.

[Abbreviations: mg/L, milligram per liter]

Analyte	Number of samples		Percentage of split samples	Difference between split samples
Analyte	Split	Total	Percentage of split samples	Median (mg/L)	Median (percent)
2002
Orthophosphate-P	19	218	9	0.01	7.4
Ammonia-N	19	218	9	.02	22.2
Nitrate/nitrite-N	19	218	9	0	0
Total phosphorus	8	114	7	.014	5.2
Chlorophyll a	14	101	14	1.6	3.4
2003
Orthophosphate-P	11	130	8	0.004	10
Ammonia-N	11	130	8	.02	16.9
Nitrate/nitrite-N	11	130	8	0	0
Total phosphorus	7	81	9	.011	7.7
Chlorophyll a	5	62	8	5	6.6
2004
Orthophosphate-P	17	191	9	0.001	6.2
Ammonia-N	17	199	9	.002	2.9
Nitrate/nitrite-N	17	191	9	.004	10.5
Total phosphorus	7	133	5	.006	4.6
Chlorophyll a	7	106	7	11	10.3

Table A3. Replicate sample results for the water-quality sample collection program, 2002–04.

[Abbreviations: mg/L, milligram per liter]

Analyte	Number of samples		Percentage of replicate samples	Difference between replicate samples
Analyte	Replicate	Total	Percentage of replicate samples	Median (mg/L)	Median (percent)
2002
Orthophosphate-P	12	218	6	0.009	10.5
Ammonia-N	12	218	6	.011	3.8
Nitrate/nitrite-N	12	218	6	0	0
Total phosphorus	6	114	5	.004	2.7
Chlorophyll a	6	101	6	4.5	4.3
2003
Orthophosphate-P	8	130	6	0.014	34.2
Ammonia-N	8	130	6	.046	19.4
Nitrate/nitrite-N	8	130	6	.005	7.2
Total phosphorus	5	81	6	.014	5.6
Chlorophyll a	4	62	6	4.5	11.2
2004
Orthophosphate-P	15	191	8	0.001	13.3
Ammonia-N	15	199	8	.016	38.6
Nitrate/nitrite-N	15	191	8	.004	12.2
Total phosphorus	10	133	8	.01	9.8
Chlorophyll a	10	106	9	11	10.5

Table A4. Spiked sample results for the water-quality sample collection program, 2002–04.

[Abbreviations: NA, not applicable (no analysis)]

Analyte	Average percentage recovery of spiked samples
Analyte	2002	2003	2004
Orthophosphate-P	112	106	92
Ammonia-N	114	94	98
Nitrate/nitrite-N	100	90	97
Total phosphorus	NA	100	104

Figure A1. Median of the difference between replicate and split samples, compared to the distribution of the environmental samples.