PERUVIAN WATER RESOURCES, CLIMATE VARIATION AND POPULATION DYNAMICS THROUGH TIME

Short-term and long-term climate variations are affecting Peruvian water resources today, and may jeopardize long-term sustainability of water supply. Although Peru has the greatest volume of glacial ice in the tropics, global warming has resulted in a 20-30% reduction of ice during the last three decades. Unusually strong ENSO events (El Nino) have altered precipitation patterns for extended periods, resulting in locally severe flooding and decreased annual precipitation in normally wet areas. Fresh water supply in Peru is adequate to support the population today, but future sufficiency is questionable. Population growth and demographic shifts may drive Peru to conditions of local and widespread water scarcity within the next two decades.

Peru’s population distribution is a relic of the Spanish occupation that began in 1530. Pre-Columbian population centers were more appropriately located in the mountainous regions of the interior, where water and agricultural resources were both more abundant. The pre-Inca Tiwanakan and Huari civilizations developed sophisticated and sustainable water and agricultural practices with canals and terraces, but may have been impacted by an extended period of drought around 1100 AD that resulted in a significant decline in their population and power. Earlier cultures, which built major temples and agricultural centers along the northeast coast of Peru, disappeared about 2800 years ago, at a time when fossil records indicate that El Niño cycles became more frequent. The Nazca culture of southern coastal Peru, developed sophisticated means of harvesting scarce ground water resources, but may have perished during a prolonged dry period.

Today the population of Peru is more than 25 million, a large percentage of who are living along the western coast. These coastal cities are quite dry, relying on water flowing to the Pacific from the mountain regions; and on ground water well systems to provide fresh water resources. Compounding the population pressures facing Peru’s water resource managers are near term declines in the renewable annual runoff, largely due to decreased accumulation, and accelerated melting of glacial ice throughout the cordilleras. The pressures of climate-induced change may again impact the sustainability of civilization in modern Peru in the near future.