A Dynamical Systems Model of the Irrigation Efficiency Paradox

In the agriculture sector, increasing irrigation efficiency (IE) by adopting more water-efficient irrigation technologies such as drip or sprinkler (among others) is generally perceived as a water-conserving practice. The basic understanding behind this perception is that increased on-farm IE leads to less water consumption at the farm, resulting in more water becoming available for use in other sectors in the basin. However, recently, many researchers show that increasing IE at the farm scale does not necessarily increase water availability at the basin scale. This phenomenon is commonly known as the Irrigation Efficiency Paradox (IEP). The primary cause of the IEP is the social behavior of irrigators or farmers towards the spare water available at the farm due to the increase in IE. In this study, we develop a dynamical systems model that captures IEP. We formulated the model based on a simple mass balance description of water flows and the farmers' social behaviors. Using this model, we identify the IEP by measuring the change in the stock of recoverable water and crop water demand that are directly influenced by the basin's hydrological parameters and the farmer's social behavior. The exhaustive numerical simulations of our model in combination with analytical calculations allow us to identify what makes a basin more vulnerable to the IEP.