Persian Gulf rain contributions, there is still a deficit of 416 cubic kilometers per year. This difference is supplied by currents at the Strait of Hormuz. The water from the Gulf has a higher salinity, and therefore exits from the bottom of the Strait, while ocean water with less salinity flows in through the top. Another study revealed the following numbers for water exchanges for the Gulf: evaporation = -1.84m/year, precipitation = 0.08m/year, inflow from the Strait = 33.66m/year, outflow from the Strait = -32.11m/year, and the balance is 0m/year. Data from different 3D computational fluid mechanics models, typically with spatial resolution
Piracy in the Persian Gulf coast of Fars during the reign of Yazdegerd II. Ibn Hawqal, a 10th-century history chronicler, alludes to piracy in the Persian Gulf in his book "The Renaissance Of Islam". He describes it as such: In Richard Hodges' commentary on the increase of trade in the Persian Gulf around 825, he makes references to Bahraini pirate attacks on ships on ships from China, India and Iran. He believes the pirates were attacking ships travelling from Siraf to Basra. Marco Polo made observations of piracy in the Persian Gulf. He states that in the seventh century, the islands of Bahrain were held