It is often assumed that investments in modern irrigation systems automatically save water. This paper, co-authored by TALANOA-WATER researchers, assesses whether this is true. We find that the impacts of modern irrigation systems are complex, and usually have the opposite effect to that intended through altered cropping and water application decisions by farmers that aggravate water scarcity. This paper investigates how the belief that modern irrigation systems automatically save water forms; why it persists, even when proven wrong by scientific evidence; and how to overcome it.