Aqualinc has previously generated a GIS layer of irrigated land in Otago, which was based on region-specific updates of the national irrigated land dataset. The most recent update was completed in 2021. The overall aim of the 2021 project was to ensure that the Otago portion of the national irrigated land spatial dataset is fit for application at a regional scale, by incorporating region specific data.ORC staff have identified that satellite imagery from the 2022-2023 summer (which was particularly dry, generating a strong contrast between irrigated and dryland areas) has highlighted a number of irrigated areas that have either changed recently, or were not captured in previous mapping. The 2023 update, which has now been completed, focuses primarily on the following areas:• Upper Taieri• Manuherekia• Alexandra• Cromwell• North Otago Irrigation scheme area• Lower Waitaki Irrigation scheme area Input datasetsThe following input datasets were used for this project:- The irrigated area map updated in 2021 by Aqualinc, which served as the base dataset for this project.- GIS layers and data tables provided by ORC:o Vineyard location mapo Horticultural land-use map- Sentinel-2 images taken in February 2023- Aerial and satellite imagery from www.basemaps.linz.govt.nz and Google Earth.Mapping methodologyThe overall approach used for this project was the same as we have used for the national dataset and previous mapping for ORC: assessing multiple lines of evidence to make a judgement on whether an area is irrigated, and what irrigation method is used.The key differences between this project and the national-scale mapping were:- The use of region-specific datasets (especially the water take consents data). - The amount of time that was able to be spent checking / investigating areas.As well as adding newly-identified features to the dataset and refining areas where the system has changed (e.g. conversion from border-dyke to pivot), some features were removed from the dataset where the updated input data did not indicate an irrigated area (i.e. “false positives” in the previous dataset).
