Chilean hydrology – changing patterns

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 final of a 3 part series, he reflects on the changes in water availability and land use in Chile. This series is based on an article published in the British Hydrological Society’s newsletter Circulation, issue 118, August 2013.

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Local concerns over dam building in Chile

Local concerns over dam building in Chile

The conscious decision to concentrate on high value grapes (for wine) and other fruit for export, along with the drought and increasing energy and water costs, is driving changes in both the operation and management of irrigation. In particular, a reliable and efficient water supply is needed if agriculture is to be internationally competitive. The older irrigation canals, built in the 19th and early 20th centuries as simple earth channels, lose 40–80% of their water into the ground and need to be lined. Furrow watering (which still accounts for 40% of irrigation) needs to be replaced by the more efficient drip irrigation.

The more advanced irrigation schemes are also applying information technology and telemetry for monitoring water availability and transfers (improving user confidence in their supply), plant and soil moisture needs (for efficient water application) and the Andes snowpack (to predict the summer runoff). At the local level, water user organizations (known as Juntas de Vigilancia) have been banding together to improve their access to finance, overcome political and institutional obstacles and allow more efficient water management, especially at times of shortages. At the national level it has been suggested that water resources administration (currently spread over several government departments) should be centralized to allow a more integrated and efficient management.

Increasing water demand has generated a range of allocation problems. The increasing requirement for irrigation is diverting water from aquifer recharge, ecosystem services and downstream wetlands. In the desert north the demands of the mines (which account for over 40% of Chile’s export earnings) conflict with domestic, agricultural, ecological and indigenous population needs.

To avoid environmentalist censure, one mining company has started to pump desalinated seawater from the coast rather than deplete the local aquifer. Pollution of rivers with mining waste is also an issue and one large development has recently been suspended until it builds satisfactory infrastructure for preventing such pollution. In the south the realisation that the extensive forest plantations can significantly affect runoff quantity and quality is driving the development of Best Management Practice and environmental certification criteria for the forestry companies.

Detecting signs of climate change is hampered by the large interannual fluctuations in conditions and also a lack of hydrometeorological stations in the Andes. The overall prediction, though, is for less rain and higher temperatures and many of the Andean glaciers are indeed in retreat. Along with the glaciers, the winter snowpack is a crucial water resource. It enables water to be stored at the time of greatest precipitation (the winter) and released at the time of greatest irrigation need (the summer). However, warming temperatures will mean less precipitation falling in solid form and melting taking place before the irrigation season, thus reinforcing the need for more storage reservoirs.

As for Valdivia, it was the scene of an early British assessment of forest hydrology. In Spanish colonial times it was an important stronghold, formidable fortifications. However, in 1820, the nascent Chilean navy, under the command of a Scot, Lord Thomas Cochrane (apparently a model for C.S. Forester’s fictional hero Horatio Hornblower), stormed the forts to gain a famous victory, effectively ending Spanish power in the south and paving the way for Chilean and Peruvian  independence. Flushed with success, Cochrane wrote to the Chilean independence leader, Bernardo O’Higgins, of the Valdivian region that “the climate is moderate and delightful and if the country were to be cleared of forest, the warmth of the ground would dissipate the moisture, eliminating the rain storms about which people seem to complain; the temperature of course is better than in England….”. He was right about the temperature but the winter rains seemed interminable. Must be the effect of all that plantation forest!

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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