Water-food Sustainability and Migration: How Could Migrants Alleviate Countries' Water Pressure?

It is commonly believed that human migrations are beneficial to the water endowments of origin countries for reducing the pressure on local resources.

However, in the paper The Water Suitcase of Migrants: Assessing Virtual Water Fluxes Associated to Human Migration  published in PlosOne we show that such belief is over-simplistic: Migrants increase the water usage destined for export because of the persistence of alimentary habits in the host country. 

Comparing the per capita quantity of water usage destined for export (that we called 'suitcase' ) with the origin country per capita water footprint, we found that, for many countries, migration phenomena is detrimental for water sustainability.

Now, the question is how country policies can reduce the negative effect of migration on water-food sustainability? How returning migrants and knowledge transfer could improve the water sustainability?