Upscaling water savings from farm to irrigation system level using GIS based agro-hydrological modelling

Irrigation continues to be the main water user on a global scale despite the increase in water use by sectors other than agriculture. More efficient water application technologies and water management practices are ways of realising potential water savings, thus moderating the negative impacts of higher water use on farm incomes and environmental impact on rivers and groundwater systems. This paper describes an integrated approach of agro-hydrological modelling for determining potential water savings achievable by adopting high-tech irrigation technologies at farm level and application of GIS techniques to upscale those benefits at the regional irrigation system level. The SWAP (Soil–Water–Atmosphere–Plant) model was used for the simulation of water use at the farm level. The results are promising, as the potential water saving ranges from 0.1 to 2.2ML ha-1 (10–220mm) for different broad-acre crops, 1.0 to 2.0MLha-1 (100–200 mm) in sprinkler and 2.0 to 3.0MLha-1 (200–300 mm) in drip irrigation for citrus, 1.0 to 1.5MLha-1 (100–150mm) in sprinkler and up to 4.0MLha-1 (400mm) in drip irrigation for vineyards and 0.5 to 1.0MLha-1 for vegetables (50–100 mm). SWAP simulations show crop water saving potential of 7% for maize, 15% for soybean, 17% for wheat, 35% for barley, 17% for sunflower and 38% for fababean from the current water use statistics in Australia. Spatial analysis in GIS environment is carried out to investigate the spatial variations of water use for a particular crop under different depths to water table and varying soil types. Maps of water need for all broad-acre crops are drawn and pixel-to-pixel comparison is performed to determine the water saving potential per unit area. The upscaling approach shows that considerable water amounts could be saved both in Murrumbidgee Irrigation Area (MIA) and Coleambally Irrigation Area (CIA) with potential water saving of 36 to 95GL (MCM) in MIA and 42 to 72GL (MCM) in CIA.