Recent reports say that one of the largest water systems, located in the ancient city of Angkor, that dates back to the preindustrial world,came close to a catastrophic breakdown before it went out of use.
The issue is that complex infrastructures such as this one consist of many interconnected parts. If one part starts to fail, chances are that another part may start failing soon. Researchers created a computer model to show how the intervals of intense rain followed by heavy droughts affected the system, especially during the 1300s when it was being used the most. The simulations showed that the biggest issue was erosion that came as a result of the water flow reaching critical levels.
Due to the higher water levels, sediment started to decrease the volume of water in freshly parched channels and this caused an uneven flow of water in the systems. If that trend continued, a complete breakdown of the water system is likely to have been imminent.
The city of Angkor itself was at one time the biggest city in the world. It was spread over a 1,000 square kilometers. Over a period of a few hundred years, the citizens meticulously built systems of canals, reservoirs, and moats that helped with water management. For some reason, the citizens of the city started abandoning it during 1400. The main reason behind this, according to the scientists, was the war with a neighboring kingdom as well as religious instability in the area due to Buddhism replacing Hinduism as the main religion of the time.
But in all honesty, the demise of the city is linked more to the climate-induced collapse of the cities infrastructure than anything else. Whenever something went wrong with the water systems, the citizens lost faith in their leader and suffered terrible losses of food reserves.