Question: I have been learning about the problems of irrigation in Mexico. Can you suggest any solutions to this problem? We saw the effect of very salty water on carrots like crops that get fed on very salty water in Mexico.

Emma Markham answered on 18 Jun 2019:

I’m not an expert on this area, but here are my thoughts. One solution would be Desalination of the soil and water, but the problem is that it can often be impractical on a large scale and could be very expensive or require a lot of equipment. Ideally there would be other sources of water which could be used for irrigation, such as a bore hole to use water held in aquifers and below the ground, as this would be filtered by the rock and not saline. However, when you start removing large quantities of water from the water table it can cause this to drop, meaning trees will die as they are unable to reach the water in the ground and this can lead to soil erosion. This could also impact local people, because their wells would run dry and they would be unable to access drinking water. Unfortunately Mexico is a country which is being impacted by climate change, as it receives less rainfall, so rivers dry out for longer and there is less water available for crops. One possibility could be to farm in polytunnels or other structures which could capture the moisture which evaporates, and recycle this, so you would not lose so much river/well water to evaporation, and so less would need to be extracted from the ground.