of nitrogen and phosphorus. These nutrients come from surrounding farmland, residential septic tanks and from the release of existing and accumulated nutrients from sediments on the lake bed. The Lake Ōkāreka Catchment Management Plan was developed in 2004. This is a long-term plan to improve the water quality of the lake, through changes like sewage reticulation, in-lake chemical treatment and farm nutrient management. It has been calculated that the load nutrients needed to reach the target TLI of 3.0 are 2.5 tonnes per year of nitrogen and 0.08 tonnes per year of phosphorus. The Trophic Level Index (TLI) is an overall indication of lake health based on a number of different criteria, values represent a three-yearly average. Better quality sites have a lower TLI. The three-yearly average for Ōkāreka indicates little change over the last five years. Lake Okareka township The township on the shores of Lake Ōkareka is described by Statistics New Zealand as a rural settlement, and covers . Lake Okareka township is part of the larger Kaingaroa-Whakarewarewa statistical area. The township had a population of 519 at the 2018 New Zealand census, a decrease of 18 people (−3.4%) since the 2013 census, and unchanged since the 2006 census. There were 183 households, comprising 255 males and 258 females, giving a sex ratio of 0.99 males per female, with 102 people (19.7%) aged under 15 years, 75 (14.5%) aged 15 to 29, 246 (47.4%) aged 30 to 64, and 87 (16.8%) aged 65 or older. Ethnicities were 94.2% European/Pākehā, 10.4% Māori, 2.3% Pacific peoples, 1.7% Asian, and 1.2% other ethnicities. People may identify with more than one ethnicity. Although some people chose not to answer the census's question about religious affiliation, 54.9% had no religion, 38.2% were Christian and 0.6% had other religions. Of those at least 15 years old, 186 (44.6%) people had a bachelor's or higher degree, and 36 (8.6%) people had no formal qualifications. 126 people (30.2%) earned over $70,000 compared to 17.2% nationally. The employment status of those at least 15 was that 210 (50.4%) people were employed full-time, 75 (18.0%) were part-time, and 9 (2.2%) were unemployed. See also Lakes of New Zealand References External links Environment Bay of Plenty - Regional Council page Lake Okareka Ratepayers' & Residents' Association Lakes of the Bay of Plenty Region Okataina Volcanic Centre Volcanic crater lakes