Storm-water infiltration and focused recharge modeling with finite-volume two-dimensional Richards equation: application to an experimental rain garden

Rain gardens are infiltration systems that provide volume and water quality control, recharge enhancement, as well as landscape, ecological, and economic benefits. A model for application to rain gardens based on Richards equation coupled to a surface water balance was developed, using a two-dimensional finite-volume code. It allows for alternating upper boundary conditions, including ponding and overflow, and can simulate heterogeneous soil-layering or more complex geometries to estimate infiltration and recharge. The algorithm is conservative, and exhibits good performance compared to standard models for several test cases (less than 0.1% absolute mass balance error); simulations were also performed for an experimental rain garden and comparisons to collected data are presented. The model accurately simulated the matrix flow, soil water distribution, as well as deep percolation (potential recharge) for a natural rainfall event in the controlled experimental setup. Read More: http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29HY.1943-7900.0000111?prevSearch=authors%3A%28Dussaillant%2C%29&searchHistoryKey

Ice Dynamics and Morphological Changes During Proglacial Lake Development at Exploradores Glacier, Patagonia

Proglacial lakes are ubiquitous features formed during deglaciarization and are currently increasing in number in Patagonia and elsewhere. Proglacial lakes can affect glacier dynamics, catchment hydrology and have the potential to cause glacial lake outburst floods. Therefore, monitoring the onset and development of proglacial lake formation is relevant to understand glacial processes and anticipate glacier response to climate change. In this study, we integrate geomorphological and ice-dynamic information to assess proglacial lake development in Exploradores Glacier, Chilean Patagonia. We monitor recent spatial and temporal changes in the lower trunk of Exploradores Glacier (10 km2) to provide a 20-year observation record by combining eight uncrewed aerial vehicles (UAV) surveys between 2019 and 2020, with high-medium resolution satellite imagery (Rapid Eye and Landsat) between 2000 and 2018. We use feature tracking techniques, digital surface elevation model analysis and field data to create a multi-temporal scale (inter-annual and seasonal) and a multi-spatial (cm to km) data set. Our analysis shows that surface velocity overall trend has not changed over the last 20 years and that surface velocity near the terminus is significant (>10 m a−1). Moreover, an exceptional advance over moraine deposits was detected. We also found low downwasting rates (<0.5 m a−1) close to the glacier terminus which are attributed to sufficient ice flux and the insulation effect of the debris-covered surface. However, hundreds of supraglacial ponds were observed and are currently coalescing and expanding by ice-cliff backwasting favoring glacier disintegration. Lastly, it was found that calving losses at the east marginal lake equaled ice-flux input into the lake for the UAV monitored period. This study contributes to a better understanding of glacial lake dynamics during proglacial lake development, and our results may help ice modelling efforts to predict glacier response to future climate scenarios

Geomorphologic impact of outburst flood cycle in braided gravel-bed rivers: confluence of Colonia and Baker rivers, Patagonia, Chile

Colonia River, as other glacial streams influenced by global warming, is affected by Glacial Lake Outburst Floods (OF). We present a study on geomorphologic features of Colonia River to comprehend the impact of OFs in sedimentary processes, analysing erosion and deposition linked to OF phenomena and frequency (since April 2008, more than 12 OFs have occurred). Interpolation analysis is carried out to create an elevation surface (DTM) from a set of sample measurements, given by contour line (2007 LiDAR) and rtkGPS point (2011 and 2012) data. These were used to create DTMs applying Delaunay triangulation. A comparisons between morphology during the current OF cycle that started on 8 April 2008, and the previous morphology (after 40 years without OFs, since end of previous cycle in 1968), is carried out through the creation of DEMs of Difference (DoDs) based on TINs. We created two DoDs, respectively between 2011-2007 (before/after the OFs cycle) and 2012-2011 (during the cycle, after the events of January and April 2012) to provide a high-resolution, spatially distributed surface model of topographic and volumetric change through time. The floodplain has been classified on the basis of the morphological characteristics: main and secondary channel(s), bars, braided area, island and delta fan features. The changes evidenced in the DoD are segregated according to these categories plus the geomorphic change taking place in each category (using GCD; Wheaton et al 2014). Issues regarding data quantity and quality will be discussed, and implications for the planned mega-dam that would flood the confluence

Magnitude and timing of Holocene glacial lake outburst floods in the Baker River, Northern Patagonian Icefield, Chile / Magnitud y frecuencia de inundaciones Holocenas generadas por vaciamiento de lagos glaciares en el Rio Baker, Campo de Hielo, Patagonico Norte, Chile

The Baker River (Southern Chile) drains a catchment of 27,000 km2 and has a mean annual discharge of 1100 m3s-1. Since last deglaciation, the morpho-sedimentology of the Baker valley has been controlled by Outburst Floods (OFs) of different scales. We apply geomorphic mapping, stratigraphy (including radiocarbon and OSL dating) and palaeoflood hydrology to reconstruct the frequency, timing and magnitude of Holocene OFs. Geomorphic mapping reveals evidence of two Holocene alluvial terraces. The oldest (highest) contains basal gravels capped by a well-developed buried Podzolic Luvisol that was radiocarbon dated to 6160±40 BP. In this alluvial sequence, at least two major floods occurred between then and 5300 BP and at least eight major floods between 5300-2500 BP. At least three Late Holocene (post 610±30 BP) GLOF event(s) inundated upper terrace surfaces along the reach downstream the confluence of the Colonia River into the Baker River. We report on the implications of this palaeoflood research in relation to the proposed HydroAysén hydroelectric scheme

Hydrological regime of remote catchments with extreme gradients under accelerated change: the Baker basin in Patagonia

The Baker basin (27 000 km2) is located in one of the most pristine and remote areas of the planet. Its hydrological regime is poised to undergo dramatic changes in the near future due to hydropower development and climate change. The basin contains the second-largest lake in South America, and part of a major icefield. This study documents the natural baseline of the Baker River basin, discusses the main hydrological modes and analyses the potential for sustainable management. Annual precipitation varies several-fold from the eastern Patagonian steppes to the North Patagonian Icefield. The westernmost sub-basins are strongly governed by glacier melt with a peak discharge in the austral summer (January–March). The easternmost sub-basins have a much more seasonal response governed by quicker snowmelt in spring (November–December), while they exhibit low flows typical for semi-arid regions during summer and autumn. Topography, vegetation and wetlands may also influence streamflow. The strong spatio-temporal gradients and variability highlight the need for further monitoring, particularly in the headwaters, especially given the severe changes these basins are expected to undergo. The great diversity of hydrological controls and climate change pose significant challenges for hydrological prediction and management

Basic theory behind parameterizing atmospheric convection

Last fall, a network of the European Cooperation in Science and Technology (COST), called “Basic Concepts for Convection Parameterization in Weather Forecast and Climate Models” (COST Action ES0905; see http://w3.cost.esf.org/index.php?id=205&action_number=ES0905), organized a 10-day training course on atmospheric convection and its parameterization. The aim of the workshop, held on the island of Brac, Croatia, was to help young scientists develop an in-depth understanding of the core theory underpinning convection parameterizations. The speakers also sought to impart an appreciation of the various approximations, compromises, and ansatz necessary to translate theory into operational practice for numerical models

APOA5 Q97X Mutation Identified through homozygosity mapping causes severe hypertriglyceridemia in a Chilean consanguineous family

BACKGROUND: Severe hypertriglyceridemia (HTG) has been linked to defects in LPL, APOC2, APOA5, LMF1 and GBIHBP1 genes. However, a number of severe HTG cases are probably caused by as yet unidentified mutations. Very high triglyceride plasma levels (>112 mmol/L at diagnosis) were found in two sisters of a Chilean consanguineous family, which is strongly suggestive of a recessive highly penetrant mutation. The aim of this study was to determine the genetic locus responsible for the severe HTG in this family. METHODS: We carried out a genome-wide linkage study with nearly 300,000 biallelic markers (Illumina Human CytoSNP-12 panel). Using the homozygosity mapping strategy, we searched for chromosome regions with excess of homozygous genotypes in the affected cases compared to non-affected relatives. RESULTS: A large homozygous segment was found in the long arm of chromosome 11, with more than 2,500 consecutive homozygous SNP shared by the proband with her affected sister, and containing the APOA5/A4/C3/A1 cluster. Direct sequencing of the APOA5 gene revealed a known homozygous nonsense Q97X mutation (p.Gln97Ter) found in both affected sisters but not in non-affected relatives nor in a sample of unrelated controls. CONCLUSION: The Q97X mutation of the APOA5 gene in homozygous status is responsible for the severe hypertriglyceridemia in this family. We have shown that homozygosity mapping correctly pinpointed the genomic region containing the gene responsible for severe hypertriglyceridemia in this consanguineous Chilean famil

Observing glacier elevation changes from spaceborne optical and radar sensors – an inter-comparison experiment using ASTER and TanDEM-X data

Observations of glacier mass changes are key to understanding the response of glaciers to climate change and related impacts, such as regional runoff, ecosystem changes, and global sea level rise. Spaceborne optical and radar sensors make it possible to quantify glacier elevation changes, and thus multi-annual mass changes, on a regional and global scale. However, estimates from a growing number of studies show a wide range of results with differences often beyond uncertainty bounds. Here, we present the outcome of a community-based inter-comparison experiment using spaceborne optical stereo (ASTER) and synthetic aperture radar interferometry (TanDEM-X) data to estimate elevation changes for defined glaciers and target periods that pose different assessment challenges. Using provided or self-processed digital elevation models (DEMs) for five test sites, 12 research groups provided a total of 97 spaceborne elevation-change datasets using various processing approaches. Validation with airborne data showed that using an ensemble estimate is promising to reduce random errors from different instruments and processing methods but still requires a more comprehensive investigation and correction of systematic errors. We found that scene selection, DEM processing, and co-registration have the biggest impact on the results. Other processing steps, such as treating spatial data voids, differences in survey periods, or radar penetration, can still be important for individual cases. Future research should focus on testing different implementations of individual processing steps (e.g. co-registration) and addressing issues related to temporal corrections, radar penetration, glacier area changes, and density conversion. Finally, there is a clear need for our community to develop best practices, use open, reproducible software, and assess overall uncertainty to enhance inter-comparison and empower physical process insights across glacier elevation-change studies

Natural disasters and indicators of social cohesion

Do adversarial environmental conditions create social cohesion? We provide new answers to this question by exploiting spatial and temporal variation in exposure to earthquakes across Chile. Using a variety of methods and controlling for a number of socio-economic variables, we find that exposure to earthquakes has a positive effect on several indicators of social cohesion. Social cohesion increases after a big earthquake and slowly erodes in periods where environmental conditions are less adverse. Our results contribute to the current debate on whether and how environmental conditions shape formal and informal institutions