the map is pretty accurate if you look at somalia for example, bay is full of farms but it does not have a river . it is because the depth of the water from underground is between 20 meters to 50 meters. if any of you guys have farms you will know that the deeper the well the more power you need to pump water out. at for example 200 meters you will need to invest in serious equipment, to much overhead for most somalis to bear.