<p>Trophic structure deterioration in continental water bodies (lakes and damps) has been a growing problem during the last years. Numerous factors, either natural or man-made contribute in value increments of various water quality indexes ranging toward eutrophication. Our study had objective to use remote sensing as complementary tool to study the spatial distribution and dynamics of Lake Vichuquén water quality parameters in two seasons of 2016 through the use of two satellite images of the Landsat 8 OLI sensor, with in situ and laboratory data. The Chl-a and Z_SD parameters were estimated from multiple linear regression models. The results indicate that the trophic state of Lake Vichuquén corresponds to a eutrophic level in summer and mesotrophic in autumn. The laboratory analyzes establish for the summer and autumn season that the Chl-a data oscillate between 14.1 and 5.5 μg/l and for the Z_SD between 3.7 and 2.5 m respectively. The increase in the levels of eutrophication of Lake Vichuquén is influenced in the first place by the seasonality and secondly by the different land uses that accelerate this type of processes; such as the plantations of radiata pine and eucalyptus, the agricultural activities and the urban areas surrounding the lake. The mean square error for each variable and each season varied in Chl-a in summer and another year 0.74 and 0.01 µg/l and Z_SD 0.16 m respectively.</p>

The upper section of the Mapocho river basin is in constant danger of landslides. This study had the objective of zoning the upper Mapocho river basin for the susceptibility of landslides using hydrological, geological, and geomorphological data. Areas with a high degree of landslide susceptibility are located on the lower part of the main valleys as well as at the headwaters of the basins. Landslide events in the mountainous region of Central Chile are caused by two main factors: intense precipitation and seismic activity.

The lengthening of the fire season in Portugal has been understudied, although there is evidence of changes in recent decades. In this brief study, we focused on the annual cycles of fire activity and related meteorological fire danger, thus bypassing the problem of subjective definition of what should mark the beginning and end of the fire season. Based on the daily time series of burned areas and occurrences collected in mainland Portugal by state services from 1980 to 2018, we searched for significant changes in the monthly and daily relative in-year distributions. In particular, an exceedance date method was used to determine day-scale trends in the anticipation/prolongation of fire activity in the year. We found an unequivocal diminishing trend in the proportion of annual burned area that occurs in the summer months (July to September), which was offset by an increase in the fraction from January to June. Apparently, the month of March plays an important role in these changes that should be clarified in future analyses. The daily analysis shows a clear shift of the cumulative curves of burned area to the left, which suggests an in-year anticipation of fire activity. Considering the dates of exceedance of the 15% of annual burned area, the found linear trend implies an anticipation rate of 1.34 days per year. Next, we evaluated seasonal changes in fire weather through the annual cycle of cumulative DSR, computed from daily FWI values. The results show, on average, an earlier increase in DSR when comparing the latter second half of the period (2000-2018) with the first one former (1980-1999). This difference develops from April to the end of September. Interestingly, a closer look shows a first increase in the gap as early as March, which disappears in April before steadily increasing again. Finally, we suggested that up-to-date knowledge of the interannual and interdecadal changes in the seasonality of both wildfires and fire weather is a decisive component, but not the only one, of a comprehensive and complex management of the fire season. A good illustration of this complexity is the fact that the annual definition of the fire season window necessarily affects the annual fire cycle by conditioning the ignition calendar.

No abstract