Just how good is the water in the Waipa River these days? Is it safe for swimming? Can fish live in it? The answer depends on which part of the river we look at.
|Kayaking, Waipā River|
At 115km long, the Waipa River is the largest tributary to the Waikato River. The Waikato Regional Council measures water quality once a month at five sites along its length ( view map ).
Water quality at each site is assessed against national standards for both human uses (such as swimming) and ecological health (plants and animals living in the river). Monitoring also indicates how water quality changes from the headwaters at Pekepeke, down through the catchment to the confluence with the Waikato River at Ngaruawahia. Find out more about how we measure water quality(external link).
There are two measures used to assess if water is suitable for human uses: bacteria levels (E. coli) and baseflow clarity.
Bacteria levels (E. coli) – are measured as an indicator of the human health risk from harmful micro-organisms present in water, for example from human or animal faeces.
Baseflow clarity (external link) – or the underwater visibility, is measured in metres, using a black disc. It is important for safety reasons to be able to see submerged objects. It is also important for aesthetics as most people prefer to see clear water in our rivers and streams. To allow good visibility for swimming you should be able to see 1.6m underwater.
Water quality in the Waipa River is generally not always good enough for swimming. Levels of E. coli bacteria (an indicator of health risk) are often above the safe level for swimming.
Levels of E. coli are much lower than they were 60 years ago because of the improvements in sewage and wastewater treatment.
E. coli comes from the dung of farm animals, animals living in the bush, such as pigs and goats, and from birds such as ducks and swans. Municipal sewage, urban stormwater and septic tank and industrial discharges are already regulated and considered to be minor sources.
Water clarity in the Waipa River is worse than in the Waikato River, due to different geology and land use. The cloudy, brown headwaters of the Waipa are due to sediment and natural tannins from bush and wetlands. The river’s appearance worsens as it flows through farmland. Sediment adds to the natural tannin to colour the Waipa murky brown.
The river fails contact recreation standards with low clarity.
Water quality for ecological health at Waipa River sites (2007-2011)
Water quality is better in the upper reaches of the Waipa River, and is good enough for most aquatic plants and animals to be healthy. The graph shows the percentage of water samples at each site that met our guidelines for water to support aquatic plants and animals (ecological health). Water quality in the lower river is not as good for plants and animals to live in as it is in the upper reaches.
Levels of the nutrients nitrogen and phosphorus, which feed nuisance plants, often do not meet ecological standards in the Waipa River. This reflects the river’s journey through an intensively farmed catchment.
Most nitrogen in the river comes from farmland, mainly cow urine. Nitrogen leaches through the soil and into groundwater. Phosphorus associated with soil washed off farmland is the main source to the river. Check out a pictograph of nitrogen levels and phosphorus levels in the river.
|July 1998 floods|
Sediment from the Waipa River changes the appearance of the water in the Waikato River when the rivers meet at Ngaruawahia. The Waikato River becomes increasingly turbid and the colour changes from green to brown.
Waikato Regional Council's Project Watershed aims to provide better, more coordinated management of river based works and services in the greater Waikato catchment. This includes the Waikato and Waipa rivers and the areas of land that drain into them.
In the photo taken in the July 1998 floods it’s easy to see where the sediment laden Waipa River meets the Waikato River at Ngaruawahia.