New Zealand Process Attribute Mapping: National surface water quality (2014-2018)

This dataset was developed to evaluate the method for Rissmann et al. (submitted to JGR Biogeosciences) 'A hydrochemically guided landscape-based classification for water quality: a case study application of process-attribute mapping (PoAM) at a national scale'. The data was produced from an independent surface water quality dataset, comprising 991 long-term monitoring sites across New Zealand. Water quality data was downloaded from Land Air Water Aotearoa (LAWA) for each year between 2014 – 2018 (https://www.lawa.org.nz/). Water quality data includes total nitrogen, nitrate nitrite nitrogen, ammoniacal nitrogen, total phosphorus, dissolved reactive phosphorus, turbidity, black disk (clarity), and E.coli as an indicator of microbial contamination. LAWA data is collected by each regional authority, with quality assurance performed according to National Environmental Monitoring and Reporting Standards (Davies-Colley et al., 2012). A minimum of 60 repeat measures are included for each site and medians calculated for the 5-year period. Before use by Rissmann et al., internal quality control in this project removed urban catchments and sites with point source impacts, including sites downstream of municipal wastewater discharges (identified as outliers), reducing the dataset to 811 sites. Site water quality medians for each monitoring point were combined with the mean process attribute gradient score for the capture zone. Process attribute gradients represent the four dominant processes controlling water composition, specifically atmospheric, hydrological, microbially mediated redox, physical and chemical weathering (see below). These process gradients are coupled with two land use gradients and catchment area above the monitoring site for water quality evaluation. Further details can be found in Rissmann et al. (submitted). Atmospheric O18 Precipitation source PPT Precipitation volume Hydrological RCD Macroscale recharge domain OLF Overland flow, OLFDL restricted to area of developed land DD Deep drainage LAT Lateral drainage ART Artificial drainage HYD Soil slaking and dispersion as a soil hydrological index NBP Soil zone bypass under soil moisture deficit EWT Equilibrium water table and aquifer potential Redox SRP Soil reduction potential GRP Geological aquifer reduction potential Weathering SGC Surface/top regolith strength BGC Basal regolith strength Geothermal GTH High enthalpy geothermal (≥180 °C)