Water is necessary to food production.
About 1000 ton of water is said to be required to product 1 ton of cereal crops, and to product foodstuffs of 1 day , about 2000 liter is said to be required.

To product 1 day foodstuffs, 10 fill of bathtub (200 liter) water is required.

So, food shortage influences to food production a lot.
Let’s think about this with example.

The reason the amount of Chinese wheat decreased and china, which used to be export country, came to import cereal crops is water.
As the altitude of groundwater came down, the water well for irrigation has been dried up.

In addition to that, in China’s Yellow River, shear flow sometimes happens.
In other countries, the number of artificial ditches for irrigation has been decreasing and shear flow happens in the Ganges, the Indus, and the Nile.

Once ago, these rivers flooded many times and carried dirt including lots of alimentation.
So, the land became richer, farming went ahead, and the civilization was constructed.

In the past and still, the river influences the production of food a lot.Food problems and water problem is widely related.

＜Words＞

・irrigation
to provide water from outside to farming land

・artificial ditches for irrigation
water provided from outside to farming land

・flood
overrunning water in a river