River and stream water quality and ecology - Greater Wellington ...

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River and stream water quality and ecology in the Wellington region: State and trends Table 4.11: Summary of meaningful trends (ie, p1% per year) in NNN, Amm N and TN concentrations (mg/L) recorded at RSoE sites over July 2006 to June 2011. MASS=median annual Sen slope (mg/L/yr) calculated using the Seasonal Kendall test. The arrow indicates the direction of the trend Site Site name Median n MASS Raw data Flow-adjusted data Rate of change (%/year) Trend n MASS Rate of change (%/year) Nitrite-nitrate nitrogen (NNN) RS05 Otaki R at Pukehinau 0.038 60 -0.003 -8.7 ↓ 60 -0.004 -10.5 ↓ RS08 Ngarara S at Field Way 0.255 60 -0.054 -21.0 ↓ Not assessed (no flow data) RS15 Porirua S at Glenside 1.000 60 -0.058 -5.8 ↓ No trend RS16 Porirua S at Wall Park 0.990 60 -0.044 -4.5 ↓ No trend RS24 Mangaroa R at Te Marua 0.484 60 -0.029 -6.0 ↓ No trend RS25 Akatarawa R at Hutt Confl. No trend 60 -0.008 -8.0 ↓ RS28 Wainuiomata R at Manuka Trk 0.075 58 -0.006 -8.3 ↓ 57 -0.006 -7.7 ↓ RS30 Orongorongo R at Orongo. Stn 0.056 59 -0.014 -25.5 ↓ 53 -0.015 -28.7 ↓ RS31 Ruamahanga R at McLays 0.025 60 -0.002 -6.9 ↓ No trend RS32 Ruamahanga R at Te Ore Ore 0.397 60 -0.037 -9.4 ↓ No trend RS33 Ruamahanga R at Gladstone Br No trend 60 -0.038 -9.5 ↓ RS36 Taueru R at Castlehill No trend 60 -0.010 -14.5 ↓ RS37 Taueru R at Gladstone 0.910 59 -0.120 -13.2 ↓ Not assessed (no flow data) RS39 Whangaehu R 250 u/s confl. 0.965 60 -0.214 -22.2 ↓ Not assessed (no flow data) RS46 Parkvale S at Weir No trend 57 -0.130 -10.5 ↓ RS49 Beef Ck at Headwaters 0.024 60 -0.003 -12.4 ↓ Not assessed (no flow data) RS50 Mangatarere S at SH 2 No trend 59 -0.051 -4.1 ↓ RS52 Tauanui R at Whakatomotomo 0.012 59 -0.001 -8.8 ↓ 59 -0.001 -12.3 ↓ Ammoniacal nitrogen (Amm N) RS08 Ngarara St at Field Way 0.03 60 -0.007 -26.7 ↓ Not assessed (no flow data) RS18 Karori S at Makara Peak 0.01 60 -0.001 -10.6 ↓ No trend Total nitrogen (TN) RS07 Mangaone S at Sims Road Br 2.60 60 -0.188 -7.2 ↓ 60 -0.117 -4.5 ↓ RS08 Ngarara S at Field Way 1.00 60 -0.100 -10.1 ↓ Not assessed (no flow data) RS15 Porirua S at Glenside No trend 60 -0.057 -4.4 ↓ RS17 Makara S at Kennels No trend 60 -0.034 -5.6 ↓ RS27 Waiwhetu S at Wainui Hill Br 0.80 59 -0.049 -6.1 ↓ 59 -0.040 -4.9 ↓ RS29 Wainuiomata R u/s of White Br 0.38 59 -0.036 -9.4 ↓ No trend RS32 Ruamahanga R at Te Ore Ore 0.56 60 -0.049 -8.9 ↓ No trend RS33 Ruamahanga R at Gladstone Br No trend 60 -0.046 -6.8 ↓ RS35 Mataikona trib at Sugar Loaf Rd 0.19 59 -0.025 -13.2 ↓ Not assessed (no flow data) RS37 Taueru R at Gladstone 1.47 59 -0.151 -10.3 ↓ Not assessed (no flow data) RS39 Whangaehu R 250 u/s confl. 1.70 60 -0.197 -11.6 ↓ Not assessed (no flow data) RS44 Totara S at Stronvar 0.15 58 -0.026 -17.2 ↓ 58 -0.020 -13.1 ↓ RS45 Parkvale trib at Lowes Res. 4.80 47 -0.298 -6.2 ↓ No flow data RS46 Parkvale S at Weir No trend 57 -0.116 -6.1 ↓ RS54 Coles Ck trib at Lagoon Hill Rd 0.23 50 -0.012 -5.4 ↓ Not assessed (no flow data) WGN_DOCS-#1100598-V3 PAGE 49 OF 160 Trend Despite a number of ‘impacted’ sites showing improvements, such as Ngarara Stream at Field Way (which now meets the ANZECC (2000) lowland TV for Amm N, Figure 4.18), in many cases the overall median values of NNN and TN are still elevated when compared against their respective ANZECC (2000)
River and stream water quality and ecology in the Wellington region: State and trends lowland TVs. For example, while the decreasing NNN trends of highest magnitude were observed at Taueru River at Gladstone and Whangaehu River 250 m from confluence (0.120 and 0.214 mg/L/year, respectively), the state analysis shows that median NNN concentrations are still well above the ANZECC (2000) lowland TV of 0.444 mg/L. The reasons for the observed trends are not clear. In the case of NNN and TN concentrations, decreasing trends were present at sites located in catchments dominated by all of the major landcover types found in the region (eg, indigenous forest, exotic forest, pastoral and urban), including a number of reference sites (eg, Otaki River at Pukehinau) and also several sites that typically record very low median NNN and TN values (eg, Akatarawa River at Hutt confluence and Taueru River at Castlehill). This suggests that the declining trends may be related to natural factors such as climate. Figure 4.18: Ammoniacal nitrogen concentrations recorded in the Ngarara Stream at Field Way, based on monthly monitoring over July 2006 to June 2011. The red and black lines denote the ANZECC (2000) lowland TV and the direction of the trend in concentrations, respectively (d) Phosphorus Meaningful trends in concentrations of dissolved reactive phosphorus (DRP) and total phosphorus (TP) were detected in raw and/or flow-adjusted data sets from 11 and 17 RSoE sites, respectively (Table 4.12). The majority of the trends represented decreasing concentrations and are indicative of potential ‘improvements’ in water quality over the reporting period. Five sites exhibited trends in both DRP and TP concentrations: Porirua Stream at Glenside, Karori Stream at Makara Peak, Kaiwharawhara Stream at Ngaio Gorge, Wainuiomata River at Manuka Track and Whangaehu River at 250 m from confluence. With the exception of the Wainuiomata site, the direction of the trends in DRP and TP concentrations were in agreement. PAGE 50 OF 160 WGN_DOCS-#1100598-V3
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DISCLAIMER This report has been pre
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observed trends were unclear. The p
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Appendix 1: Monitoring site details
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