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

Abstract

Freshwater inputs strongly influence oceanographic conditions in coastal systems of northwestern Patagonia (41–45°S). Nevertheless, the influence of freshwater on these systems has weakened in recent decades due to a marked decrease in precipitation. Here we evaluate potential influences of climate and land cover trends on the Puelo River (640 m3s–1), the main source of freshwater input of the Reloncaví Fjord (41.5°S). Water quality was analyzed along the Puelo River basin (six sampling points) and at the discharge site in the Reloncaví Fjord (1, 8, and 25 m depth), through six field campaigns carried out under contrasting streamflow scenarios. We also used several indicators of hydrological alteration, and cross-wavelet transform and coherence analyses to evaluate the association between the Puelo River streamflow and precipitation (1950–2019). Lastly, using the WEAP hydrological model, land cover maps (2001–2016) and burned area reconstructions (1985–2019), we simulated future land cover impacts (2030) on the hydrological processes of the Puelo River. Total Nitrogen and total phosphorus, dissolved carbon, and dissolved iron concentrations measured in the river were 3–15 times lower than those in the fjord. Multivariate analyses showed that streamflow drives the carbon composition in the river. High streamflow conditions contribute with humic and colored materials, while low streamflow conditions corresponded to higher arrival of protein-like materials from the basin. The Puelo River streamflow showed significant trends in magnitude (lower streamflow in summer and autumn), duration (minimum annual streamflow), timing (more floods in spring), and frequency (fewer prolonged floods). The land cover change (LCC) analysis indicated that more than 90% of the basin area maintained its land cover, and that the main changes were attributed to recent large wildfires. Considering these land cover trends, the hydrological simulations project a slight increase in the Puelo River streamflow mainly due to a decrease in evapotranspiration. According to previous simulations, these projections present a direction opposite to the trends forced by climate change. The combined effect of reduction in freshwater input to fiords and potential decline in water quality highlights the need for more robust data and robust analysis of the influence of climate and LCC on this river-fjord complex of northwestern Patagonia.

Forest Fires, Land Use Changes and Their Impact on Hydrological Balance in Temperate Forests of Central Mexico

“…Between 1995 and 2008, the area of temperate forest decreased by 57.6 ha, but in the period of 2008-2021, 323.9 ha were lost, and the sum of the changes in both periods amounted to a decrease of 16.3% (Table 4), mainly because the surface of the lower temperate forest was affected by two forest fires that occurred in 2012 and 2017 [55,56] (see Supplementary Materials: Figure S2). The changes in land use as a consequence of a high frequency of forest fires coincide with the results of [57]. Highly severe forest fires have the potential to interrupt a wide variety of hydrological processes and functions in forested watersheds, such as interception, infiltration, evapotranspiration, and storage [58,59], and their effects can result in an increase in surface runoff and erosion and an increase in the sediment on the riverbeds [60][61][62].…”

“…The decrease in evapotranspiration of 6.5% in the Chapingo River microbasin, 3.6% in the Texcoco River, and 4.8% in the San Bernardino River is also related to the alteration of the hydrological balance [57,84]. The results coincide with the effects of land use changes on the hydrological components in the Chongwe River basin presented by Tena et al [85], showing that the actual annual evapotranspiration decreased from 840.6 mm to 796.3 mm due to a decrease of 41.11% in forest cover.…”

“…Therefore, in degraded areas, there would be a considerable advance in rainfed agricultural areas (64.2%), which would take the place of what would preferably be forested areas. Under these conditions, the model indicates that surface runoff would increase [54,57] in the three microbasins: Chapingo River (68.2%), Texcoco River (85.4%), and San Bernardino River (49.9%). The elimination of vegetation cover and soil organic matter will lead to changes in the hydrological processes by reducing the interception of precipitation and modifying the structure of the surface soil [14,15,82].…”

Bioclimatic influence on water chemistry and dissolved organic matter in shallow temperate lakes of Andean Patagonia: A gradient approach

“…In the Andean Patagonian region (Argentina), precipitation has decreased by up to 9% per decade and is projected to continue to decrease (Aguayo et al, 2021;Bianchi et al, 2016;Pessacg et al, 2020). Meanwhile, temperatures have risen, reducing winter snowfall and snow accumulation, causing earlier spring snowmelt, and increasing evapotranspiration in summer (Aguayo et al, 2021;Barros et al, 2015;León-Muñoz et al, 2021).…”

“…In the Andean Patagonian region (Argentina), precipitation has decreased by up to 9% per decade and is projected to continue to decrease (Aguayo et al., 2021; Bianchi et al., 2016; Pessacg et al., 2020). Meanwhile, temperatures have risen, reducing winter snowfall and snow accumulation, causing earlier spring snowmelt, and increasing evapotranspiration in summer (Aguayo et al., 2021; Barros et al., 2015; León‐Muñoz et al., 2021). Decreasing precipitation and warming are leading to strong hydrological shifts, reducing the lateral runoff and streamflow (Masiokas et al., 2008; Pessacg et al., 2020) and, consequently, the C and nutrient fluxes towards freshwaters (Queimaliños et al., 2019).…”