3. Water Quality Monitoring Data
3.1 E.coli concentrations
Since early 1998, quarterly spot samples have been collected at the 73 stream and river sites across the Waikato region for E.coli analysis. This analysis is done by membrane filtration with a count on MFC agar at 44.5° C after 24 hours, following the American Public Health Association method 9222G. At most locations 15 samples have been collected to date. Mean values are often markedly higher than median values (Table 1) reflecting the strong positive skewness of the data distributions. Analysis is therefore focused upon the median values as they better describe the central tendency of the data. Median concentrations range from 1 to 1300 cfu/100mL (Table 1) with the highest values generally associated with the most intensive dairy farming in the centre of the region (Figure 3), for example the Komakorau, Mangakotukutuku, Mangaone, Mangawhero and Oraka streams (sites 33, 41, 45, 51, and 64 respectively). The lowest median values are generally found in forested catchments bordering Lake Taupo in the south, for example, the Waihaha, Hinemaiaia, and Kuratau rivers, and the Whanganui and Mapara streams (sites 3, 28, 34, 23, and 53 respectively). The impact of land use upon median E. coli concentration is illustrated in Figure 7. Of the 73 sites, median values at 53 of them exceed the guideline for freshwater recreation (126 cfu/100mL). The range in values found at a site (Table 1) can be extremely large (for example at the Waitawhiriwhiri stream and the Waitoa and Mokau rivers, sites 14, 17, and 57 respectively) reflecting significant temporal variation in factors contributing to faecal contamination (and die-off), for example, point sources, stock density, the magnitude of streamflow, and insolation.
Table 1. Statistical summary of spot sampled E. coli and turbidity at the 73 sites. IQR = Interquartile Range.
|
E. coli (cfu/100mL) |
Turbidity (NTU) |
|||||||||
|
Num |
Site |
N |
Mean |
Median |
StdDev |
IQR |
Mean |
Median |
StdDev |
IQR |
|
1 |
Waerenga Stm |
15 |
1266 |
400 |
3251 |
348 |
15 |
4 |
41 |
4 |
|
2 |
Waiau River |
15 |
767 |
140 |
2204 |
160 |
13 |
3 |
29 |
7 |
|
3 |
Waihaha River |
15 |
20 |
4 |
36 |
15 |
1 |
0 |
0 |
0 |
|
4 |
Waihou River |
15 |
251 |
230 |
106 |
168 |
3 |
3 |
2 |
2 |
|
5 |
Waihou River |
15 |
61 |
33 |
88 |
32 |
0 |
0 |
0 |
0 |
|
6 |
Waiohotu Stm |
15 |
230 |
110 |
340 |
228 |
3 |
3 |
1 |
1 |
|
7 |
Waiomou Stm |
15 |
328 |
330 |
158 |
220 |
3 |
3 |
1 |
2 |
|
8 |
Waiotapu Stm |
15 |
3 |
1 |
6 |
2 |
7 |
6 |
3 |
3 |
|
9 |
Waipa River |
15 |
1129 |
390 |
1596 |
1183 |
22 |
10 |
33 |
15 |
|
10 |
Waipa River |
15 |
501 |
200 |
963 |
253 |
6 |
4 |
8 |
6 |
|
11 |
Waipapa Stm |
15 |
110 |
89 |
118 |
45 |
3 |
3 |
1 |
1 |
|
12 |
Waitahanui River |
15 |
70 |
60 |
46 |
55 |
1 |
1 |
0 |
0 |
|
13 |
Waitakaruru River |
15 |
1502 |
230 |
4570 |
330 |
17 |
10 |
30 |
10 |
|
14 |
Waitawhiriwhiri Stm |
15 |
2753 |
700 |
3364 |
3774 |
48 |
29 |
52 |
12 |
|
15 |
Waitekauri River |
15 |
382 |
180 |
773 |
258 |
2 |
1 |
4 |
1 |
|
16 |
Waitetuna River |
15 |
625 |
380 |
481 |
543 |
14 |
8 |
13 |
13 |
|
17 |
Waitoa River |
15 |
1701 |
370 |
2523 |
2556 |
8 |
5 |
9 |
5 |
|
18 |
Waitoa River |
15 |
1140 |
430 |
1820 |
970 |
9 |
6 |
11 |
8 |
|
19 |
Waitomo Stm |
15 |
1753 |
740 |
3211 |
1270 |
20 |
12 |
24 |
14 |
|
20 |
Waitomo Stm |
15 |
1731 |
190 |
4313 |
1053 |
12 |
6 |
13 |
11 |
|
21 |
Waiwawa River |
15 |
2270 |
170 |
7951 |
360 |
9 |
2 |
25 |
1 |
|
22 |
Whakauru Stm |
15 |
677 |
300 |
1280 |
353 |
3 |
3 |
1 |
1 |
|
23 |
Whanganui Stm |
3 |
38 |
28 |
25 |
35 |
1 |
1 |
0 |
0 |
|
24 |
Wharekawa River |
15 |
1425 |
250 |
4314 |
430 |
4 |
2 |
4 |
1 |
|
25 |
Whareroa Stm |
3 |
102 |
140 |
65 |
85 |
3 |
2 |
1 |
1 |
|
26 |
Whareroa Stm |
3 |
114 |
160 |
88 |
119 |
3 |
3 |
1 |
2 |
|
27 |
Hikutaia River |
15 |
648 |
280 |
1036 |
458 |
3 |
1 |
6 |
2 |
|
28 |
Hinemaiaia River |
15 |
28 |
26 |
16 |
23 |
1 |
1 |
0 |
0 |
|
29 |
Karapiro Stm |
15 |
695 |
440 |
820 |
678 |
10 |
4 |
14 |
4 |
|
30 |
Kauaeranga River |
15 |
330 |
120 |
747 |
237 |
2 |
1 |
4 |
1 |
|
31 |
Kawaunui Stm |
15 |
868 |
600 |
755 |
1380 |
4 |
4 |
1 |
2 |
|
32 |
Kirikiriroa Stm |
15 |
1366 |
600 |
2225 |
516 |
49 |
33 |
52 |
15 |
|
33 |
Komakorau Stm |
15 |
127769 |
1300 |
490273 |
923 |
53 |
55 |
18 |
30 |
|
34 |
Kuratau River |
3 |
21 |
28 |
15 |
21 |
9 |
2 |
14 |
18 |
|
35 |
Little Waipa Stm |
15 |
160 |
140 |
80 |
85 |
2 |
1 |
1 |
1 |
|
36 |
Awakino River |
14 |
136 |
70 |
138 |
120 |
9 |
2 |
17 |
7 |
|
37 |
Awakino River |
14 |
873 |
220 |
1416 |
840 |
75 |
5 |
187 |
25 |
|
38 |
Mangaharakeke Stm |
15 |
160 |
160 |
85 |
85 |
4 |
4 |
1 |
1 |
|
39 |
Mangakara Stm |
15 |
226 |
160 |
196 |
165 |
4 |
4 |
1 |
2 |
|
40 |
Awaroa Stm |
15 |
25007 |
240 |
95440 |
320 |
8 |
5 |
9 |
4 |
|
41 |
Mangakotukutuku Stm |
15 |
1637 |
1200 |
1898 |
1301 |
30 |
24 |
20 |
16 |
|
42 |
Mangamingi Stm |
15 |
660 |
250 |
771 |
643 |
3 |
3 |
0 |
1 |
|
43 |
Manganui River |
14 |
536 |
176.5 |
899 |
450 |
58 |
3 |
109 |
30 |
|
44 |
Mangaohoi Stm |
14 |
160 |
78 |
232 |
60 |
5 |
2 |
10 |
2 |
|
45 |
Mangaone Stm |
15 |
1143 |
900 |
822 |
1183 |
10 |
6 |
15 |
4 |
|
46 |
Mangaonua Stm |
15 |
2216 |
900 |
2977 |
1233 |
23 |
11 |
30 |
6 |
|
47 |
Mangaonua Stm |
15 |
6517 |
400 |
22561 |
436 |
71 |
3 |
257 |
2 |
|
48 |
Mangapu River |
15 |
2296 |
370 |
7120 |
597 |
26 |
8 |
64 |
11 |
|
49 |
Mangatutu Stm |
14 |
575 |
235 |
521 |
890 |
9 |
3 |
13 |
5 |
|
50 |
Mangauika Stm |
15 |
277 |
12 |
592 |
31 |
4 |
1 |
11 |
1 |
|
51 |
Mangawhero Stm |
15 |
1788 |
1000 |
1837 |
1998 |
49 |
41 |
29 |
10 |
|
52 |
Mangawhero Stm |
15 |
330 |
90 |
558 |
357 |
25 |
7 |
61 |
7 |
|
53 |
Mapara Stm |
15 |
105 |
92 |
55 |
72 |
4 |
3 |
1 |
1 |
|
54 |
Marokopa River |
15 |
634 |
190 |
798 |
1148 |
12 |
4 |
22 |
8 |
|
55 |
Mokau River |
14 |
872 |
315 |
1106 |
1400 |
449 |
41 |
1161 |
80 |
|
56 |
Mokau River |
15 |
620 |
100 |
1409 |
122 |
3 |
3 |
3 |
2 |
|
57 |
Mokau River |
14 |
2053 |
450 |
3996 |
2580 |
80 |
10 |
132 |
133 |
|
58 |
Mokauiti Stm |
14 |
2745 |
355 |
5428 |
1360 |
158 |
16 |
294 |
44 |
|
59 |
Ohautira River |
15 |
2495 |
450 |
7354 |
493 |
19 |
10 |
29 |
7 |
|
60 |
Ohinemuri River |
15 |
1110 |
170 |
2462 |
569 |
5 |
2 |
7 |
2 |
|
61 |
Ohinemuri River |
15 |
1452 |
97 |
4590 |
530 |
4 |
1 |
11 |
1 |
|
62 |
Ohote Stm |
15 |
613 |
266 |
840 |
483 |
16 |
9 |
12 |
21 |
|
63 |
Opuatia Stm |
15 |
1297 |
240 |
2590 |
450 |
18 |
8 |
35 |
10 |
|
64 |
Oraka Stm |
15 |
1213 |
1300 |
667 |
1010 |
4 |
3 |
2 |
3 |
|
65 |
Otamakokore Stm |
15 |
213 |
190 |
112 |
125 |
2 |
2 |
1 |
1 |
|
66 |
Piako River |
15 |
1218 |
330 |
2761 |
804 |
9 |
4 |
12 |
3 |
|
67 |
Piako River |
15 |
1106 |
510 |
1339 |
1040 |
14 |
9 |
14 |
5 |
|
68 |
Piakonui Stm |
15 |
588 |
110 |
1166 |
360 |
8 |
4 |
8 |
3 |
|
69 |
Pokaiwhenua Stm |
15 |
168 |
130 |
113 |
176 |
2 |
2 |
1 |
1 |
|
70 |
Pueto Stm |
15 |
48 |
32 |
59 |
15 |
2 |
2 |
1 |
1 |
|
71 |
Tahunaatara Stm |
15 |
107 |
93 |
73 |
64 |
2 |
2 |
0 |
0 |
|
72 |
Tairua River |
15 |
609 |
140 |
1719 |
231 |
4 |
2 |
5 |
1 |
|
73 |
Tapu River |
15 |
608 |
190 |
1103 |
278 |
4 |
2 |
6 |
1 |
Figure 7. Boxplots illustrating log transformed median E. coli statistics from sites characterised by greater than 90% non-pastoral vegetation, and those characterised by greater than 90% pastoral vegetation. The outlined central box depicts the middle half of data between the 25th and 75th percentiles, the horizontal line across the box marks the median, the whiskers extend from the top and bottom of the box to depict the extent of the main body of data. Outliers are plotted individually as a circle.
3.2 Turbidity
Sampling for turbidity was undertaken at the same time as sampling for microbial analysis (section 3.1) for each of the 73 sites. As with the microbial dataset considerable variance is evident within many sites (Table 1). Median turbidity varies significantly across the region, ranging from < 1 to 55 Nephelometric Turbidity Units (NTU). This range reflects the spatial and temporal diversity of processes determining hillslope and channel sediment dynamics.
Contact for Enquiries
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