The Mangahahuru Stream, which begins in Pinus radiata forestry southeast of Hikurangi, is a small tributary of the Wairua River. This site is located in the upper catchment and therefore the landuse is predominately exotic forestry. It was added to the River Network in 2005-2006, to include a hard sedimentary, exotic forestry site to the network. It is also a good comparison for the Mangahahuru Stream site at Apotu Road.
The first year of results for the Mangahahuru Stream at Apotu Road are summarised in the table below including the median, range and percentage of sampling occasions that comply with relevant guidelines for the 12 sampling occasions. Medians shown in red are outside the recommended guidelines.
|Parameter||Median||Range||% comply with guideline|
|Temperature (deg. cel.)||14.5||9.8 - 19.3|
|Dissolved oxygen (mg/L)||10.0||8.6 - 12.9||100|
|Dissolved oxygen (% Sat.)||96.4||93 - 114||33|
|Conductivity (mSm)||9.7||8.7 - 10|
|Water clarity (m)||2.08||0.75 - 2.95||100|
|Turbidity (NTU)||3.5||2.6 - 13.1||83|
|E. coli (n/100mL)||204||20 - 2247||25|
|Dissolved reactive phosphorus (mg/L)||0.005||0.002 - 0.01||100|
|Total phosphorus (mg/L)||0.018||0.015 - 0.033||100|
|Ammoniacal nitrogen (mg/L)||0.005||0.005 - 0.02||100|
|Total nitrogen (mg/L)||0.146||0.107 - 0.526||100|
|pH||7.2||6.7 - 7.4||50|
As expected this new site on the Mangahahuru Stream appears to have much better water quality than the site at Apotu Road. In general this site has relatively good water quality, with consistently low nutrient levels and moderate to good water clarity i.e. met their respective guidelines 100% of the time. However bacterial levels are often elevated, only meeting the freshwater bathing guideline of 126/100mL on three sampling occasions.