Petition Mobile water desalination vessels for drought areas

Instead of Britain delivering massive ammounts of cash to assist in ever increasing droughts with no real results I suggest that a series of mobile water desalination vessels be funded by UK. Old oil tankers could be refitted to become mobile water desalination units. Take on sea water and produce fresh water, stored in shipboard tanks. Vessels would remain at sea until such time as the tanks are full. They would only touch land to discharge the stored fresh water before sailing in open waters to produce more. A number of ships, in rotation, could produce a frequent regular supply at each port.