Adaptation to climate change in irrigated agriculture: an evolutive water footprint approach.

Abstract

In a rapidly changing global scenario due to climate change, there is a need to improve the way we treat our increasingly scarce natural resources. As agriculture is the most waterconsuming productive sector in the world, it becomes a priority focus on these efforts. A lot of works had pointed out what are the best adaptation measures to climate change impacts on agriculture, however little is known about what are the best ways to implement these measures, especially when are included in the problem variables such: financial limitations, power gaps between large and smallholder farmers, and losses in productivity due to decreases in water availability. This work aims to develop a methodology to determine optimal adaptation strategies for water use in irrigated agriculture using the water footprint as an efficiency/sustainability indicator to guide the process. SPEA2, a second-generation evolutionary algorithm, was used to find optimal solutions, and Aquacrop OS was used to estimate the farmer’s water footprint. Through this, it is possible to determine a set of Pareto solutions with the two main objectives of the adaptation process: increase water use efficiency/sustainability and minimize the cost to do so. The adaptation strategy is generated in several steps, in a way that the same importance is given to the mid rages and the final result of the process. To test the develop methodology, a practical study case was simulated using River Mamuaba basin (a sub basin from River Gramame basin), located in the Paraiba state in northeast Brazil. For the study case, observing the Pareto frontiers for all decades, some general recommendations could be extracted to the farmers. For the firsts decades, until a certain cost, the reduction in water footprint per unit of money invested is more gainfull than beyond that point, while at the end of the adaptation period, it is better to choose cheaper measures. It was also suggested to make more changes that enhance the system’s efficiency than changes that replace different kinds of crops. Very small and small farmers were prioritized in the adaptation process, making the approach more holistic. Water Footprint benchmarks are also suggested to serve as reduction targets to guide and helps to monitor the adaptation strategy implementation process on the ground.