Modelling the Effects of Changes in Forest Cover and Climate on Hydrology of Headwater Catchments in South-Central Chile

Abstract

This study analyses the changes in the runoff of forested experimental catchments in south-central Chile, to determine to what extent observed trends can be attributed to effects of intensive forestry and/or climate change. For this, we applied the distributed TETIS® model to eight catchments (7.1−413.6 ha) representative of the land uses and forestry activities in this geographical area. Rainfall and runoff data collected between 2008 and 2015 were used for modelling calibration and validation. Simulation of three land uses (current cover, partial harvest and native forest) and 25 combinations of climatic scenarios (percentage increases or decreases of up to 20% of rainfall and evapotranspiration relative to the no-change scenario applied to input series) were used in each calibration. We found that changes in land use and climate had contrasting effects on runoff. Smaller catchments affected by the driest climatic scenarios experienced higher runoff when the forest cover was lower than under full forest cover (plantations or native forests). In contrast, larger catchments under all climatic scenarios yielded higher runoff below the full forest cover than under partial harvest and native forest. This suggests that runoff can be influenced, to a great extent, by rainfall decrease and evapotranspiration increase, with the model predicting up to a 60% decrease in runoff yield for the dry’s climatic scenario. This study proves to be relevant to inform ongoing discussions related to forest management in Chile, and is intended to minimize the impact of forest cover on runoff yield under uncertain climatic scenarios.

Estimation of the Climate Change Impact on the Hydrological Balance in Basins of South-Central Chile

“…Specifically in Chile, Stehr et al [24] modeled the hydrological response to climate change in two sub-basins of the Biobío River, depicting that a 30% decrease in precipitation could conduct a 45% and 32% reduction in the water flow of the study sub-basins. In addition, Barrientos et al [64] recently reported an study also conducted in experimental sub-basins of the BioBio river obtaining similar results in the trends. Even when these forecasts suggest more dramatic reductions in precipitation and runoff than the present study, the observed trends become similar.…”

Climate and Land Cover Trends Affecting Freshwater Inputs to a Fjord in Northwestern Patagonia

“…In the worst scenario for winter (SC-3), the hydrological model predicts changes of −2.0%, −2.4% and 8.6% on the base flow, interflow and runoff, respectively. The magnitude of projected changes is comparable to a deforestation scenario in the Vergara River Basin (Stehr et al, 2010), but lower than what was reported in south-central Chile, where changes in LCC are relatively more drastic and different (intensive forestry; Aguayo et al, 2016;Barrientos et al, 2020;Martínez-Retureta et al, 2020).…”

Plantaciones forestales y rendimiento hídrico

“…La comparación temporal antes y después de la tala de la tercera cuenca produjo una mayor escorrentía estival resultante de la tala de una parte significativa de la plantación de Pinus radiata, lo que también sugiere un mayor consumo de agua bajo un uso de suelo de plantación forestal. Barrientos et al (2020) analizaron los cambios en la escorrentía de cuencas experimentales forestadas en el centro-sur de Chile, para determinar en qué medida las tendencias observadas pueden atribuirse a los efectos de la silvicultura intensiva y/o al cambio climático. Aplicaron el modelo TETIS distribuido a ocho cuencas (7 entre 1-100 ha, y otra de 413 ha) representativas de los usos del suelo y las actividades forestales en la Cordillera de la Costa chilena de la región del Biobío, cerca de la ciudad de Nacimiento (37° S).…”