Climate variability in high elevation areas in the basins of the Imperial and BioBío Rivers
Under the framework of the EcoAdapt Project in Chile, a research process has begun to study the water context in the BMAAM territory (Caracautin and Lonquimay). The study entitled "Study of the Climate Variability of High Elevations in the watersheds of the Imperial and Biobío Rivers: Instrumental Approaches," and authored by Ariel Muñoz, explores the challenges behind the creation of development measures for adaptation to changes in climate.
According to the author, the quantity and quality of the instrumental records in Chile is limited. Despite having a large amount of distributed weather stations across the country, it is still not possible to easily obtain access to complete and longstanding instrumental climate records. However, from a total of 127 analyzed stations ("fluviometrical" and meteorological) between the regions of Bio Bio and Araucania, 15 weather stations and 9 fluviometrical stations were used. The results are shown inter alia in Rainfall variability; Variations in temperature and large-scale climatic Forcing (ENSO, SAM); The stated goal was to determine what were the major changes in the recent climate in the Andean areas of the basins of the Imperial and Biobío Rivers, through the analysis of instrumental records available.
The study area is located between 37º - 40ºS, in the center-south of Chile. Meteorological records were compiled by the Directorate General of Water (DGA), part of the Ministry of Public Works of Chile.
To analyze changes and trends in precipitation and temperature in the area, the study used regional composite series. These regional series are based on a series of stations that are highly correlated. The comparison period was between 1992-2012, which corresponded to annual values expressed as standardized anomalies.
Principal Results from the Study
- The precipitation showed a tendency to decrease in the study area, which was most marked from mid 1970-1980, mainly in the precipitation of the fall and spring seasons which had greater reductions.
- The reduction in precipitation at high elevations has been close to 15% since the mid 70's. This analysis is limited by the extension of the registers in these altitude levels. However, through the relationships between these records and those located at lower elevations, it follows that the percentage of current reduction in rainfall is around 30% relative to the amount of rainfall recorded in the first half of the twentieth century.
- Changes in temperature were clearly detectable only in the case of minimum temperatures, which are increasing significantly as of the mid 70's. The recurrence of severe droughts has increased in the area. The change has been quite dramatic over the last 100 years. Both in winter and summer severe droughts (lower 10th percentile) have changed from occurring every twenty years on average to happening every six years on average today. While this is an average value, this knowledge could be a real factor of consideration in agriculture and water management. In this context, one should bear in mind that every 6 years on average, severe droughts may occur, which may be considered in planning crops, harvests, plantations and fruit production, and other farming activities. This can also be useful information for water management as it could help to promote the storage of the water resources during non-drought years.
- The minimum temperature has increased by almost two degrees (1.8 degrees Celsius) in the last decade compared to the average of the 47 years of record. Meanwhile the average and maximum temperatures have increased between 0.3 and 1 degree Celsius.
Climate forcing (ENSO , SAM ):
- In relation to the large-scale climate forcings (El Niño, the Southern Oscillation - ENSO, AAO), there were different relationships with the climate of the area, although all of them had a shared influence on the climate of the region. From the analysis developed in this work, we conclude that ENSO has a greater influence on precipitation, and a weaker relationship with temperature. Meanwhile, the AAO has a significant effect on both precipitation and temperature over the area, possibly even being the main modulator of the climate in the area.
- In relation to flow variability at different elevations, the results suggest that both in areas of low, and mid-elevation areas, water availability has fallen sharply in the last sixty years, particularly in the summer, autumn and spring. At low elevations winter flows have also been reduced, however the winter flows in areas of high elevation have increased during the last decades. Meanwhile, no trends were observed in mid-elevation areas, constituting one gradient variation of the flows according to the elevation of the seasons that were analyzed .
- Possibly the most interesting result from the point of view of climate change and potential adaptation measures was that winter flows have increased in areas of high elevations, which could be explained by an increase in elevation on the zero isotherm, which would relate to the increase in minimum temperatures found in this study. This could result in the accrual of liquid water being greater in areas where previously the water had been in the form of snow.
One of the main conclusions of the study presented by the author, is that given the significant changes in climate observed in this study, it is considered highly relevant to install and maintain instrumental records in areas of high elevations, in order to better understand how local climate changes in each geographical area of the country. This approach could provide more precise measures for the development of policies and adaptation to the local climate change results. Regardless, the results can generate lines of work involved in an adaptation strategy.
This information allows the project to initiate a process by key stakeholders to come up with a strategy for water management.