Dessert and dry areas
A sea water desalination system supplied by solar electric power near the shore needs for the photovoltaic only 0.8% of the surface to irrigate with 500mm water a year.
Accoring to usual economic calculation, a sea water desalination system can produce water for 0.48 EUR per m³. There are 0.25 EUR energy cosst for 2.5 kWh with 10 Cent and 0.23 EUR for financing expenses and service included. The caluclation is with the for 2020 expected solar electric power prices in areas with much solar energy. The desalination system could become so much cheaper, that one m³ is for only 0.40 EUR.
1 ha dry land
Further comes the distribution of the water. In areas near the coast about 20 Cent. To irrigate 1 ha with 500mm water makes 3000.-EUR a year. At higher places up to 500m above sea level, the distribution costs could be 60 Cent and so for 500m irrigation 5000.-EUR per year.
= 500mm Water