2. The concept of rainwater catchment systems technology is as old as the mountains - The history of rainwater harvesting

Rainwater harvesting has been a popular technique in many parts of the world, especially in arid and semiarid regions (almost 30 % of the earth's surface) (Fig. 1). Rainwater harvesting was invented independently in various parts of the world and on different continents thousands of years ago. It was especially used and spread in semiarid areas where rainfall occurs only during some months and at different locations.

I would like to illustrate this with some examples:

In the loess plateau of China (Ganzu Province), rainwater wells and jars existed already two thousand years ago.
In India, a research project called the Dying Wisdom lists many traditional experiences in rainwater harvesting from the different 15 environmental zones of that country.
In Iran we find the Abanbars (Fig. 3), the traditional rainwater catchment systems for communities.

2000 years ago an integrated rainwater management and runoff agriculture existed in the Negev desert of Israel and Jordan.
As a representative of the Americas, I will say some words about the Pre-Columbian practices of the Maya people in the Yucatan, Mexico. Mexico as a whole is rich in ancient and traditional rainwater harvesting technologies (dating back to the Aztecs and Mayas).
South of the city Oxkutzcab on the foot of the Puuc Mountain we can still see the achievements of the Mayas. In the 10th century AD an integrated agriculture based on rainwater harvesting existed in this region. The people lived on the hillsides and their drinking water was provided by 20 to 45 thousand liters cisterns called Chultuns (Fig.2). These cisterns had a diameter of more or less 5 m and were excavated in the lime subsoil with a waterproof plaster. Above them there was a ground catchment area of 100 to 200 m². In the valleys below (Fig.2) other types of rainwater catchment systems were used such as Aguadas (artificially dug rainwater reservoirs from 10 to 150 million liters) and Aquaditas (small artificial reservoirs from 100 to 50 000 liters).
It is interesting to see that the aguadas and aguaditas were used to irrigate fruit trees and/or forests and to provide water for the plantation of vegetables and corn on small areas. Lots of water was stored, guaranteeing water supply even during unexpected droughts. This is one example of integrated water management and we can find many similar ones all over the world.