THE FUTURE OF WATER SUPPLY IN COASTAL PERU AS CLIMATE CHANGE AND SHRINKING GLACIERS DIMINISH RUNOFF

Perú, with the greatest concentration of glaciers in all of the tropics, is dependent on runoff from its cordilleras for water for hydroelectric generation, irrigation and drinking water supply. Rapid recession of the mountain glaciers will lead to reduced meltwater contribution to stream flow, and diminished water availability in the near future. Huge infrastructural investments are being made to obtain water for the arid Pacific coastal plain; home to nearly 70% of Perú’s 29 million people.

At the current rate of growth, Perú’s capital, Lima, will have a population of 15 million within 25 years. Water supply to Lima, which is barely adequate for the population today, will need to be doubled. Today, a network of reservoirs, canals and tunnels are being developed to capture the headwaters of the Rio Mantaro, which flows east to the Amazon basin.

North and south of Lima, major diversions of west-flowing rivers have been proposed or constructed to support irrigation of extensive agricultural areas. Sustainability of water supply to these developments is questionable in light of climate change and already conflicts have developed between small-scale farmers in the highlands and large-scale, government-supported water diversions to the fertile coastal plain.

Desalination of the Pacific waters is often proposed as the next step to sustainable supply for Lima, and several projects have been proposed or completed to enhance supply for Lima and other coastal cities. Hydropower is also likely to diminish as a result of the on-going deglaciation of the Andes. Alternatives to hydropower will require either construction of new thermal generating capacity with increased combustion of fossil fuels, or the development of large scale renewable energy projects. Both will be very expensive and may well be beyond the capabilities of Perú. Large scale supply of fresh water from desalination may well be out of reach of the Peruvian economy.