is the amount of phosphorus dissolved in water and is most immediately and readily absorbable for plant and algae growth. It is one component of , the other being phosphate that is stuck to sediment and is therefore unavailable for plants.
Current national state
Current water quality across the whole country is estimated using models, which are based on data collected from hundreds of monitoring sites over a five year period to 2012.
Modelling and site data indicate that higher DRP concentrations generally occur in the Waikato, through parts of the Hawke's Bay and the Manawatu regions and in Southland.
Thebelow shows the modelled dissolved reactive phosphorus concentrations for four different .
Modelling predicts thatDRP concentrations in rivers draining urban, pasture and exotic forest land covers are 2-3 times higher than those draining catchments with predominately .
Rivers and streams draining pasture catchments have the widest range of concentrations, ranging from the highest in the country to some of the lowest. Such variability might be due to high variability in erosion, combined with a wide range of different pastoral farming practices and intensities.
Overall, across all land cover types, the number of monitoring sites where improving dissolved reactive phosphorus trends (DRP) were detected (40%) outweighed those that showed a deteriorating trend (11%). Because this pattern occurred over all land covers, it may be due to factors unrelated to management such as long term climate variation.