Examination of water budget using satellite products over Australia

Abstract

Large-scale water balance in the Australian continent is examined over an 8-year period (2003–2010) with three commonly used satellite based water cycle components: precipitation (P) from the Tropical Rainfall Measuring Mission (TRMM), evapotranspiration (ET) from the Moderate Resolution Imaging Spectroradiometer (MODIS), and terrestrial water storage change (ΔS) from the Gravity Recovery and Climate Experiment (GRACE). First we evaluate the water balance using the three products over areas with limited annual streamflow to eliminate the influence of runoff in the analysis. We observe more frequent and better closure and consistency in the water balance from the three components over the central part of Western Australia, where low precipitation, high elevation and low relief exist. The data are more coherent at seasonal and annual scales compared to the monthly scale. Application of the three products in Lake Eyre Basin (an internal drainage system) suggests a maximum 6.2 mm/year groundwater inflow to the basin, which is consistent with the regional groundwater flow direction in the area. This result also indicates that the absolute integrated error of the combination of three products should be smaller than 6.2 mm/year, which is about 2.1% of annual precipitation in the basin. If this relative error is assumed for the whole continent, water balance calculation using the three products over the whole Australian continent results in 144.7 ± 11.3 mm/year estimated total runoff to the surrounding oceans during the study period. We found that this estimate is comparable to the estimates of 50–150 mm/year from the Australian Bureau of Meteorology and National Water Commission.