Uploaded on 2020-08-29 by Photo of Riyadh from Private Jet

City of Makkah "Mecca" is located in the western side of the Saudi Arabia. in Hajj season, over 3 million pilgrims come to Makkah from all over the world, in which food becomes a huge form of flow that getting stocked at least 2 months prior to the Hajj season. People themselves, flow, to the city and they require many services such as transportation, food, lodging accommodation, and even a strong sewage system as a stock. Another form of stock is the groceries and many other shops who operate across the year, but even become four times larger in the season of Hajj, also, the locals are sort of stock that don't leave the city in this season. Water is a strong example of flow in the city of Makkah which is located around 60 miles from Jeddah, the coasty city. Thus, sea water get treated to become drinkable and then stored in the form of stock in dedicated reservoirs over the year. Makkah has many forms of interchangeable elements as stock and flow. Also, the city always experiences a high-level of complexity to run and understanding the needed stocks and flows in crucially important to run Makkah.