Irrigated agriculture potential of Australia’s northern territory inferred from spatial assessment of groundwater availability and crop evapotranspiration

Agricultural expansion has been a hot topic in the Northern Territory (NT) of Australia in recent years. However, insufficient information on available water resources and crop evapotranspiration is a bottleneck to this expansion. Towards closing this gap, this study employs the newest Global Land Data Assimilation System (GLDAS; version 2.2) catchment products assimilated from the Gravity Recovery and Climate Experiment (GRACE; hereafter called GLDAS-DA) and the Food and Agriculture Organization (FAO) Penman-Monteith equation to spatially evaluate the Balance between water availability (i.e., groundwater and effective rainfall) and melons, maize and citrus crop evapotranspiration (water demand) of three representative (short-, medium-season and perennial) crop types over the NT for the 2010–2019 period. Specifically, this Balance is the estimated ratio of water availability and crop evapotranspiration, representing the crop area that can be planted in each GLDAS-DA grid cell. The larger the Balance, the greater the irrigated agriculture potential. Under the average 2010–2019 conditions, our results show that the northern part of the NT has the highest irrigated agriculture potentials with the average Balance of 9430 ha (15.7%), 5490 ha (9.1%) and 3520 ha (5.8%) for melons, maize and citrus, respectively, excluding non-agriculture areas. Irrigated agriculture in the central part of the NT shows less potential compared to the northern part of the NT, with the average Balance of 2780 ha (4.6%), 2000 ha (3.3%) and 970 ha (1.6%) for melons, maize and citrus, respectively (excluding non-agriculture areas). The southern part of the NT shows an average Balance below 1% of grid cell for all three crops, suggesting that only small-scale irrigated agriculture could be possible. In addition, the Balance across most of the northern and central parts of the NT decreased by 50% or more during 2019 dry period. Drought risk management should therefore be a serious consideration when exploring further expansion of irrigated agriculture in the NT.