Despite being the driest inhabited continent, Australia has one of the highest per capita water consumptions in the world. In addition, instead of having fit-for-purpose water supplies (using different qualities of water for different applications), highly treated drinking water is used for nearly all of Australia's urban water supply needs, including landscape irrigation. The water requirement of urban landscapes, particularly urban parklands, is of growing concern. The estimation of evapotranspiration (ET) and subsequently plant water requirements in urban vegetation needs to consider the heterogeneity of plants, soils, water, and climate characteristics. This research contributes to a broader effort to establish sustainable irrigation practices within the Adelaide Parklands in Adelaide, South Australia. In this paper, two practical ET estimation approaches are compared to a detailed Soil Water Balance (SWB) analysis over a one year period. One approach is the Water Use Classification of Landscape Plants (WUCOLS) method, which is based on expert opinion on the water needs of different classes of landscape plants. The other is a remote sensing approach based on the Enhanced Vegetation Index (EVI) from Moderate Resolution Imaging Spectroradiometer (MODIS) sensors on the Terra satellite. Both methods require knowledge of reference ET calculated from meteorological data. The SWB determined that plants consumed 1084 mmyr(-1) of water in ET with an additional 16% lost to drainage past the root zone, an amount sufficient to keep salts from accumulating in the root zone. ET by MODIS EVI was 1088 mmyr(-1), very close to the SWB estimate, while WUCOLS estimated the total water requirement at only 802 mmyr(-1), 26% lower than the SWB estimate and 37% lower than the amount actually added including the drainage fraction. Individual monthly ET by MODIS was not accurate, but these errors were cancelled out to give good agreement on an annual time step. We conclude that the MODIS EVI method can provide accurate estimates of urban water requirements in mixed landscapes large enough to be sampled by MODIS imagery with 250-m resolution such as parklands and golf courses.

The effects of roots on soil-moisture measurements taken with a neutron probe were studied. These effects were observed under three different soil-moisture conditions, with different sized roots, and with varying distances between the access tube and root. The moisture conditions used were air dry, field capacity, and saturated. Large roots can greatly affect neutron soil-moisture measurements when the access hole is drilled through the root. Positive errors as large as 52 percent were found when the soil moisture was at field capacity. With dry and saturated conditions positive errors of 43 percent and 38 percent respectively, were found. In most practical field situations, where the access hole is not drilled through large roots, root material appears to have very little effect, if any, on neutron soil-moisture measurements. The largest positive error found, when the access holes were not drilled through the roots, was only 8 percent. This occurred at a point where the access tube was in contact with the outside of a root