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.