Assessing water quality limits and risks from intensified irrigation development: A New Zealand case study

摘要: Irrigation development is being promoted by the New Zealand government alongside need to set catchment limits for water takes and protect quality. This paper presents results of an integrated management assessment potential quality consequences from proposed Waimea augmentation project near Nelson, Zealand. The comprised four components: 1. Modelling nutrient leaching through soil profile six land uses, irrigated dryland, groups using SPASMO model. 2. Assessing attenuation nitrogen carried via three aquifers bottom potentially sensitive receiving waters (springs, river coast). 3. Recommending which values uses those waters, 4. Scoping possible Good Management Practices (GMPs) would reduce risks exceeded when increased irrigation implemented. Full modelled increase concentrations entering groundwaters 23% in a hypothetical worst case up 50% if entire plains were converted market gardening. These increases, however, are mitigated (diluted) drainage rates groundwater 6% 19% respectively caused irrigation. Nitrogen diluted dispersed within with around unconfined aquifer 0-40% confined aquifers. In river, expected improve scheme operating, because dilution offered uncontaminated flow releases dam. Spring-fed streams fed upwelling Upper Confined already have high - albeit declining nitrate 4.6-14 mg/L, legacy past use. Those springs identified as 'choke points' system based on toxicity aquatic species may be exceeded.