- Name of measurement site: Puujoki
- Location: Janakkala, Leppäkoski
- Catchment area: Puujoen drainage basin, (1035 km2)
- Coordinates (ETRS-TM35FIN): P:6748701, I: 376227
The Puujoki drainage basin consists of the upstream Pääjärvi (220 km2), Teuronjoki (460 km2) and Puujoki (352 km2) catchments. Fields comprise 28% of the total area, but in Puujoki sub-catchment theiy contribute 38% of the area. The measurement point is situated at 80 m a.s.l. in Leppäkoski, which is <3 m below the sampling site in Teuronjoki river. Similar to the Teuronjoki sub-catchment, the soils consist of clayey silt, sandy gravels, moraine and organic soils, and fields situate mostly close to the stream on fine soil material. Until the beginning of 2000 treated wastewaters from Hausjärvi municipality were discharged into Punkajoki river, which is a tributary of Puujoki. On-line measurements were started in December 2013, and since then also reference samples for water chemistry analyses have been collected year-round.