## Water Consumption at the Basin Scale and Trends in WUE  
### WUE and Water Consumption at the Basin Scale  
The need for water users to achieve greater WUE is often seen as a prerequisite for saving water for the benefit of other users as well as the environment. However, literature reviewed suggests that a higher WUE does not necessarily equal to net water saving, particularly at the basin scale. When seen from the dimension of a water basin, what may be assessed as a loss in one perspective (e.g., deep drainage losses that may occur in surface systems), may be a gain in another way (e.g., recharge of groundwater resources). Some research has shown that significant improvement in delivery and on-farm WUE may in fact lead to a decline in groundwater resources ([PERSON] et al., 2016) or reduce water for environment and downstream users ([PERSON] et al., 2017). Therefore, although improvement of on-farm irrigation WUE may lead to water savings on the farm, it will not necessarily be beneficial on a catchment or basin scale ([PERSON] et al., 2016). An overall increase of water consumption at the basin scale may occur if water savings ultimately leads to an expansion of the irrigated area ([PERSON] et al., 2016). This was demonstrated by research conducted in Morocco which saw the overall water consumption rise as a result of subsidised drip irrigation kits promoted as a means of increasing productivity and saving water ([PERSON] et al., 2016). In this example, although the drip system is generally regarded as water-efficient, farmers were found to shift to more water-intensive crops and generally used the \"saved\" water to expand the acreage under irrigation. This view has been corroborated by other studies, for instance a FAO-funded research project undertaken in North Africa and the Middle East region ([PERSON] et al., 2016). The study found that at the field scale, water saving may appear to be substantial, but at the basin scale, the total water consumption may actually increase while the crop water productivity gains for the most important crops may be modest at best. In a study undertaken in India, the widespread adoption of water efficient methods such as the sprinkler and drip systems were found to have the capacity to substantially reduce overextraction of groundwater resources, but half of the water saved was reused to expand the area under irrigation ([PERSON] et al., 2016). Figure 4 is used as an example to demonstrate the simultaneous increasing uptake of water-efficient technologies (sprinkler and drip) and the increasing total area under irrigation (especially between 1994 and 2013) in the Unites States. This suggests the potential reuse of any water savings to expand the area under irrigation. The graph in Figure 4 also shows the corresponding decrease in surface irrigation systems that are generally regarded as inefficient. An analysis of the MDB in Australia showed that the environment may become the unintended casualty (receive less water on average) of the increases in WUE driven by the adoption of water-efficient technologies [47] with most of the saved water being reused. The reuse of the saved water seems to be corroborated by the trend of the total irrigation water use in Australia between 2002 and 2017 (Figure 5). The graph shows that the total irrigation water use between 2002 and 2006 was above 10,000 gigalitres (GL) but reduced to a low of just above 6000 GL in the four-year period: 2007-2008 and 2010-2011. The reduced irrigation water use in the period 2006-2011 was as a result of a severe drought that drastically reduced the availability of water for irrigation. In the period 2012-2014, the water use increased back to a similar level to the early part of the available data (approximately 11,000 GL), effectively signalling no net water saving. There was a decrease of irrigation water use in 2014-2016, but increased slightly in 2016-2017 to just over 9000 GL. The trends appear to be largely dependent on weather patterns.