An Analysis of the Effects of Large Wildfires on the Hydrology of Three Small Catchments in Central Chile Using Tritium-Based Measurements and Hydrological Metrics

Abstract

Wildfires are an important disturbance affecting catchments’ soil and hydrological processes within. Wildfires are predicted to increase in both frequency and severity under climate change. Here, we present measurements of tritium (3H) in surface water of three streams before and after the ‘las Máquinas’ megafire of January 2017 in central Chile and streamflow metrics. Mean transit times (MTTs) of water were calculated in three coastal catchments with the Mediterranean climate type, covered by native forest, a mixture of native forest and Pinus radiata D. Don, and P. radiata. Lumped parameter models (LPMs) were used to obtain MTTs. Tritium activities from 2012 to 2018 ranged from 0.597 to 0.927 Tritium Units (TU), with the lowest TU activity in 2018. These 3H concentrations indicated water ages from 5 to 30 years. Following the fire, peak flows and baseflow have increased in two catchments but decreased in the third. Even though we have seen changes in the hydrological responses within the three catchments, pre- and post-fire MTT values were not significantly different. Therefore, there is no conclusive evidence of hydrological changes at the groundwater level due to wildfire at this early stage. However, since the MTT ranges from 5 to 30 years, it is likely that more time is required for the changes in the hydrograph to be clearly reflected in the tritium signal even though there are noticeable changes in streamflow metrics such as runoff and baseflow. Within the following years from this study, a sampling schedule to continue to investigate both the long-term drought and the effect of wildfire on these catchments will be maintained.

A Multi-Model Multi-Scale Approach to Estimate the Impact of the 2007 Large-Scale Forest Fires in Peloponnese, Greece

“…Although no wide consensus has been established with regard to the questions posed in this work, we believe that there is a favorable perspective for this, which is justified by the recent intensification of related research efforts worldwide (e.g., [69][70][71][72], to mention but a few.) Additionally, one should not lose sight of the fact that many anthropogenic influences act simultaneously (e.g., forest fires, deforestation, large-scale hydraulic works) and affect the same hydrological variables by: (i) altering the rate of evaporation, (ii) modifying the velocity and amount of overland flow, (iii) altering the amount of infiltration into the ground, and (iv) affecting the amount of intercepted water [73].…”

Geochemical and isotopic tracers to define the aquifer’s vulnerability: the case study of the alluvial multi-aquifer system of the Friulian plain

“…Geochemical and isotopic analysis was used to investigate the origin of the water samples collected and analyzed, discriminating the different types of water, and understanding their interactions. This approach is widely used in literature especially to date water resources with wide applications both in Italy (Mayer et al, 2014 ; Romano et al, 2018 ; Telloli et al, 2022 ), in Europe (Balocchi et al, 2022 ; Brkić et al, 2020 ; Malov, 2021 ), and all over the word (Copia et al, 2020 ; Varol et al, 2020 ).…”

“…Specific markers were identified highlighting the differences between groundwater and other types of water using the dissolution kinetics of carbonates (rCa/rMg ratio and isotope ratio of δ 18 O and δ 2 H) (Jesiya et al, 2021 ; Li et al, 2019a ) and the 3 H isotope (Li et al, 2019b ; Niu et al, 2020 ). These analyses permit defining the average age of the resources as the time required for the recharge contributions to compensate for the losses induced by exploitation and resurgence (Balocchi et al, 2022 ; Barbieri, 2019 ). Furthermore, these data allow estimating the critical values of depletion that can compromise the quality and quantity of the resource.…”

The Large-Scale Effect of Forest Cover on Long-Term Streamflow Variations in Mediterranean Catchments of Central Chile

“…This relationship was significant during dry seasons (October through March) and stronger between December and January (Figure 5), with an intra-catchment pattern revealing that the greater the area or fraction of mixed forests with native forest dominance in the MC catchments, the greater the tendency to find increases in average, maximum, and minimum monthly streamflow (Figure 5). This unique feature representing the hydrologic response could be a clear signal of coevolutive patterns at the ecosystem timescales, in which any other abrupt natural or anthropogenic disturbances of the landscape (i.e., forest fires, tree die-off, deforestation, and land use changes) can affect the hydrologic response at local or catchment scales (Figure 5) (for reference, see [83][84][85][86]). The fact that more native and mixed forests are present in an MC catchment could increase the infiltration capacity of soils and the capacity of the catchment to regulate subsurface flow, whose release to the main streamflow of these rivers starts between August and September, when the catchments are still under near-saturated water conditions, and it can be sustained until the end of summer in February, March or even April in some very wet years.…”