Recreational Bathing Water Quality
The overall findings from the 2005-06 summer survey were that most of the rivers throughout Northland during dry weatherwere generally acceptable for swimming and other freshwater recreational activities. However after heavy and/or prolonged rain, the waterways became unsuitable for several days afterwards.
Exceptions were Lake Waro and Langs Beach, Ocean Beach, Otiria and Wairoa Streams, which were all generally unsuitable for freshwater contact in all conditions. Otiria and Langs Beach streams are of the most concern as E. coli levels were consistently above the alert threshold over the entire summer. Lake Waro has had good water quality in the past in terms of bacterial levels. It is thought that the problems that arose during the 2005-06 summer are mostly as a result of faecal material from high numbers of wild fowl on the lake. Whangarei District Council have reduced their numbers and this site will be closely watched next summer.
Alternatively the water quality of the other two lakes sampled, Ngatu on the Aupouri Peninsula and Taharoa in the Kai iwi lakes group, were generally excellent over the entire 2005-06 survey. This indicated that microbiological water quality was consistently suitable for recreational bathing.
Lakes are not as susceptible to rainfall as rivers and streams are, particularly the dune lakes of Northland, which do not have any significant surface inflows. For more information on the results for 2005-2006, view the lake monitoring section.
Interim grades, based on the national guidelines developed by Ministry for Environment and Ministry of Healt, were calculated for all sites with data stretching back over at least five summers. The process has tended to overstate the health risks at some sites due to the high rainfall Northland experiences with its semi tropical climate and as Northland's current recreational bathing programme is still short of the 20 weeks that the national guidelines recommend and are based on. All the sites with enough data have been graded as either "poor" or "very poor" with the exception of Lakes Ngatu and Taharoa.
The table below shows the median and 95th percentile for E. coli per 100 mL based on the last five surveys at all ongoing sites with their interim SFRG grade. Note: Sites are ranked by their median E. coli counts.
|Location||Median E. coli (No./100mL)||95th percentile (E. coli/100mL)||Interim grade|
|Lake Taharoa||5||122||Very Good|
|Omamari Beach Stream||160||1248||Poor|
|Waitangi River||189||2525||Very Poor|
|Lake Waro||259||2951||Very Poor|
|Kerikeri River||275||6593||Very Poor|
|Waitaua River||399||4788||Very poor|
|Wairoa Stream||660||6723||Very Poor|
|Ocean beach stream||711||6867||Very poor|
|Otiria Stream||1122||3716||Very Poor|
|Langs beach stream||1254||3914||Very poor|
Finally, it must be stressed that any findings presented cannot be taken as absolute conclusions. In all likelihood the Langs Beach, Otiria and Wairoa stream sites are not the only unsafe sites in Northland and just because many of the sites were relatively good over the summer months does not necessarily make them suitable all year round, let alone from year to year. It is probably best that, if you are unsure of the quality of a given swimming site, then that site should be considered potentially unsafe until you know otherwise.