Chilean hydrology – setting the scene

Dr James Bathurst, of the School of Civil Engineering and Geosciences at Newcastle University, has been on sabbatical at the Universidad Austral de Chile at Valdivia during April-August 2013, researching the impact of forest plantation on soil erosion.

In this three-part series, he sets the scene of Chilean hydrology and water resources. This series is based on an article published in the British Hydrological Society’s newsletter Circulation, issue 118, August 2013.

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Dr James Bathurst on the Baker River Ferry

Dr James Bathurst on the Baker River Ferry

Improbably thin, Chile stretches from within the tropics to Cape Horn at a latitude equivalent to Edinburgh, providing just about every hydro-logical environment except tropical rain forest. North to south, it can be split into the Atacama Desert (so dry that NASA uses it as a Mars analogue), a central region grading from Mediterranean climate (Santiago annual rainfall 360 mm) to temperate rain forest (Valdivia 2500 mm) and a cold and even rainier southern region (over 3000 mm in Patagonia). Water so defines the southern end of the Central Valley that two of Chile’s administrative regions are named ‘The Lakes’ and ‘The Rivers’. West-east there are significant variations from the Coastal Cordillera, across the Central Valley and into the Andes, where snowmelt and glaciers form important water sources. Volcanoes and earthquakes add their own hydrological impacts.

The climate is strongly affected by the El Niño Southern Oscillation and is characterized by alternating sequences of wet and dry years. Since 2010 the country has been enduring a severe drought, with the last decade being the driest for 70 years. In May 2013, at the start of the austral winter, the nation’s reservoirs were on average in deficit by -71% relative to the normal May figure, with many of the irrigation reservoirs at less than 5% capacity. It is predicted that four wet years are needed to recharge them fully.

Agriculture is the main water user (63%), industry takes around 25% and domestic use is around 11%. Some double use of water occurs for hydropower. Most of Chile’s reservoirs are for hydropower and irrigation whilst most domestic water comes from river extraction or wells. Typically the hydropower reservoirs are built and owned by the generating companies while irrigation reservoirs involve much greater state funding.

The 1981 Water Code established a framework in which free-market forces and water markets were allowed to trade water rights and enable the reallocation of water to high-value uses, such as fruit and wine. Known as the Chilean Model it had some success in its aims but did not take into account social considerations. In 2005 it was therefore reformed to address social equity and environmental protection concerns, so that for example ecological water flows and sustainable aquifer management must now be considered in the granting of new water rights. Too late, though, for the northern rivers, where the water rights were assigned before the environment was considered a priority. In some cases the sum of the water rights exceeds the available water.

Sources and acknowledgements

Most of the above information was taken from Wikipedia and El Mercurio, which regularly discusses water-related issues and which endeared itself to me by once publishing a special supplement containing Manning’s flow resistance equation. I thank Andrés Iroumé (Universidad Austral de Chile), Alejandro Dussaillant (University of Greenwich and Centro de Investigaciones en Ecosistemas de la Patagonia) and Claudio Meier (Universidad de Concepción) for additional information and for checking what I have written but I remain responsible for any misrepresentation. I also thank Andrés as my host at the Universidad Austral de Chile, Chile’s Comisión Nacional de Investigación Científica y Tecnológica (CONICYT) (MEC contract 80120037) as my financial sponsor and my colleagues at Newcastle University (who took on my duties) for enabling me to undertake such a fascinating and enriching sabbatical.

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