Water scarcity in Northern and Central Chile

Among the several issues that can limit the Chile’s development, scarcity of fresh water is identified as an outstanding problem. In a country that still bases its economic growth in the exploitation of natural resources, water is much required in agriculture, mining and hydro-power, as well as for human consumption.

perc_paine2The increasing demand of water resources is in collision course with the scarcity of this element in north-central Chile. The northern part of the country (18-30S) holds most of the mining activity along the Atacama desert, arguably the driest place on earth with less than 10-20 mm/year.

The only input of water there is the convective rainstorms that occur over the high Andes during summertime (the so-called Bolivian winter) feeding small creeks and recharging the aquifer system of Pampa del Tamarugal. Winter storms become more frequent as one moves southward, but annual rainfall in central Chile does not exceed 500 mm for the most part. Fortunately, much of the winter precipitation contributes to the seasonal snow cap of the subtropical Andes, which melting during spring-summer support the river flow that is used in agriculture.

If the balance between water supply and water demand is nearly tie in present day, the future looks worrying. On the one hand, economic growth implies increasing demand even though usage efficiency is enhanced. On the other hand, climate models consistently project a substantial decrease of the precipitation over central Chile (33-40S), extending southward the water-stressed region. The reduction, relative to present conditions, can be as large as 30-40% under a high GHGs emission scenario (A2) for the end of the century (Fuenzalida et al, 2007).  We need to sharp our projections of the hydrological cycle during the 21st century. This implies the use of more advanced, higher-resolution modeling tools to gauge the long-term trends produced by anthropogenic climate change (MO) but also a better assessment of the natural variability of the climate system, including interannual and interdecadal fluctuations (CD). Use of paleo-climate data (e.g., tree rings, lake sediments) will be an important tool to determine the typical amplitude and recurrence of longer term climate fluctuations, since they are poorly represented in the short historical records. Also, a careful analysis of the current legal framework for water resources is in place.

(a) We need to properly transfer the projected changes in climate drivers (precipitation, temperature) into hydrological change. CR2 researchers have already contributed to project mean changes of surface hydrology (river runoff), but much work is needed in assessing changes in extreme events and subsurface resources (ground water). Within the CD component of our center we plan to estimate present and future recharge rates to understand groundwater systems in two pilot basins in Northern Chile.

(b) The projected changes in water resources (trends and variability) will be employed by the ECO group to assessing impacts in agriculture and natural vegetation communities. Likewise, the HD group will use this information to better quantify economic and social impacts, and eventually to propose changes in the legal system to better cope with the increased scarcity of water resources.

(c) CD in conjunction with BGC and HD will assess the question of reliability and trends in camanchaca as a non-conventional source of water for human consumption.