Trends

Are things getting better or worse?

Variables important to aquatic ecosystems, such as turbidity, clarity, ammoniacal nitrogen, E. coli and faecal coliforms have again been seen to improve significantly at Regional Council monitoring program sites (table 3.2). Those parameters are typical of point source pollution (refer to Appendix 5.10 for graphs demonstrating trends for parameters measured).

Harris Ck and Duck Ck were the most improved, which both had improved ammoniacal nitrogen, faecal coliforms and clarity. Faecal coliforms and clarity improved at Murray Ck and Mawheraiti River. Clarity and ammoniacal nitrogen improved at Orowaiti River at the Excelsior Rd monitoring site. There is agricultural activity above all these monitoring sites and improved water quality may stem from changes to farm management practices within these catchments.

Sites on some of the much larger West Coast rivers, like the Grey and Buller, also showed improvements in clarity and ammoniacal nitrogen over a twenty year time frame. Improvements in clarity were no longer apparent at any NIWA sites for the last ten years with two sites showing significant declining trends in clarity. Dissolved reactive phosphorus and nitrate, along with total nitrogen, have increased at many NIWA sites. Being large rivers, their nutrient levels are a culmination of many sources hence they should be indicative of their many sub-catchments. Earlier West Coast Regional Council analysis in 2008 concluded that point source pollution has decreased, but diffuse source pollution has increased, and these patterns are similar to those evident in other parts of New Zealand. This most recent analysis continues to support this theory but suggests that improvements associated with better managed point source pollution may be slowing.

Page reviewed: 21 Aug 2015 2:41pm