Extreme and long-term drought in the La Plata Basin: event evolution and impact assessment until September 2022

The current drought conditions across the Parana-La Plata Basin (LPB) in Brazil-Argentina have been the worst since 1944. While this area is characterized by a rainy season with a peak from October to April, the hydrological year 2020-2021 was very deficient in rainfall, and the situation extended into the 2021-2022 hydrological year. Below-normal rainfall was dominant in south-eastern Brazil, northern Argentina, Paraguay, and Uruguay, suggesting a late onset and weaker South American Monsoon and the continuation of drier conditions since 2021. In fact, in 2021 Brazilian south and south-east regions faced their worst droughts in nine decades, raising the spectre of possible power rationing given the grid dependence on hydroelectric plants. The Paraná-La Plata Basin drought induced damages to agriculture and reduced crop production, including soybeans and maize, with effects on global crop markets. The drought situation continued in 2022 in the Pantanal region. Dry meteorological conditions are still present in the region at the end of September 2022 with below-average precipitation anomalies. Soil moisture anomaly and vegetation conditions are worst in the lower part of the La Plata Basin, in the southern regions. Conversely, upper and central part of the basin show partial and temporary recovery

Sediment source fingerprinting: benchmarking recent outputs, remaining challenges and emerging themes

Abstract: Purpose: This review of sediment source fingerprinting assesses the current state-of-the-art, remaining challenges and emerging themes. It combines inputs from international scientists either with track records in the approach or with expertise relevant to progressing the science. Methods: Web of Science and Google Scholar were used to review published papers spanning the period 2013–2019, inclusive, to confirm publication trends in quantities of papers by study area country and the types of tracers used. The most recent (2018–2019, inclusive) papers were also benchmarked using a methodological decision-tree published in 2017. Scope: Areas requiring further research and international consensus on methodological detail are reviewed, and these comprise spatial variability in tracers and corresponding sampling implications for end-members, temporal variability in tracers and sampling implications for end-members and target sediment, tracer conservation and knowledge-based pre-selection, the physico-chemical basis for source discrimination and dissemination of fingerprinting results to stakeholders. Emerging themes are also discussed: novel tracers, concentration-dependence for biomarkers, combining sediment fingerprinting and age-dating, applications to sediment-bound pollutants, incorporation of supportive spatial information to augment discrimination and modelling, aeolian sediment source fingerprinting, integration with process-based models and development of open-access software tools for data processing. Conclusions: The popularity of sediment source fingerprinting continues on an upward trend globally, but with this growth comes issues surrounding lack of standardisation and procedural diversity. Nonetheless, the last 2 years have also evidenced growing uptake of critical requirements for robust applications and this review is intended to signpost investigators, both old and new, towards these benchmarks and remaining research challenges for, and emerging options for different applications of, the fingerprinting approach

Erosión y desertificación.-Assessment of the effectiveness of soil and water conservation measures in reducing runoff and soil loss: establishment of a European database

ABSTRACT Soil erosion by water is recognised as a major soil degradation process that requires a global approach. Large regions all over the world are in need of integrated conservation strategies that sustainably prevent and remediate soil erosion. Therefore, quantitative and globally interpretable data are needed in support of models and decision making. The effects of various soil and water conservation techniques (SWCT) on runoff and soil loss in Europe have been extensively studied over the last 60 years. Runoff plots are the most widely used measurement technique to study the effects of SWCT on runoff and soil loss by water erosion. Hence, many data are available. However, the insights gained hereby remain mostly local and often qualitative whereas the full potential of the available data is not exploited yet. This is mainly due to the fragmentation of knowledge and extrapolation difficulties inherently linked with this type of data. This study addresses the issue of the availability of quantitative runoff and soil loss data from plot measurements in Europe and the quantitative assessment of the effectiveness of various SWCT in reducing runoff and soil loss. In the framework of the EU-DESIRE project, a database is currently compiled. The database currently contains 3175 plot-year data on runoff and soil loss measurements from 108 study sites in Europe and the Mediterranean. The SWCT documented herein include crop rotations, conservation tillage, cover cropping, mulching, vegetated buffer strips and terraces. From this dataset, an evaluation can be made of the effectiveness of various SWCT in reducing runoff and soil loss by water for a range of environmental conditions in Europe. A first example, regarding the effectiveness of SWCT in olive orchards, is discussed in this paper

How effective are soil conservation techniques in reducing plot runoff and soil loss in Europe and the Mediterranean?

The effects of soil and water conservation techniques (SWCTs) on annual runoff (R a), runoff coefficients (RC a) and annual soil loss (SL a) at the plot scale have been extensively tested on field runoff plots in Europe and the Mediterranean. Nevertheless, a comprehensive overview of these effects and the factors controlling the effectiveness of SWCTs is lacking. Especially the effectiveness of SWCT in reducing R a is poorly understood. Therefore, an extensive literature review is presented that compiles the results of 101 earlier studies. In each of these studies, R a and SL a was measured on field runoff plots where various SWCTs were tested. In total, 353 runoff plots (corresponding to 2093 plot-years of data) for 103 plot-measuring stations throughout Europe and the Mediterranean were considered. SWCTs include (1) crop and vegetation management (i.e. cover crops, mulching, grass buffer strips, strip cropping and exclosure), (2) soil management (i.e. no-tillage, reduced tillage, contour tillage, deep tillage, drainage and soil amendment) and (3) mechanical methods (i.e. terraces, contour bunds and geotextiles). Comparison of the frequency distributions of SL a rates on cropland without and with the application of SWCTs shows that the exceedance probability of tolerable SL a rates is ca. 20% lower when SWCT are applied. However, no notable effect of SWCTs on the frequency distribution of RC a is observed. For 224 runoff plots (corresponding to 1567 plot-year data), SWCT effectiveness in reducing R a and/or SL a could be directly calculated by comparing measured R a and/or SL a with values measured on a reference plot with conventional management. Crop and vegetation management techniques (i.e. buffer strips, mulching and cover crops) and mechanical techniques (i.e. geotextiles, contour bunds and terraces) are generally more effective than soil management techniques (i.e. no-tillage, reduced tillage and contour tillage). Despite being generally less effective, no-tillage, reduced tillage and contour tillage have received substantially more attention in the literature than the other SWCTs. Soil and water conservation techniques are generally less effective in reducing R a than in reducing SL a, which is an important consideration in areas where water is a key resource and in regions susceptible to flooding. Furthermore, all SWCTs show a more consistent and effective reduction of both R a and SL a with increasing R a and SL a magnitude, which is attributed to the reduced influence of measurement uncertainties. Although some significantly negative correlations between SWCT effectiveness and plot slope length, slope gradient or annual precipitation were found, the importance of these factors in explaining the observed variability in effectiveness seems limited. Time-series analyses of R a during multiple years of SWCT application strongly indicate that no-tillage and conservation tillage become less effective in reducing R a over time. Such an effect is not observed for SL a. © 2012 Elsevier B.V

Sediment yield as a desertification risk indicator

Soil erosion is often regarded as one of the main processes of desertification. This has led to the use of various desertification indicators that are related to soil erosion. Most of these indicators focus, however, on small spatial units, while little attention has been given to the amount of sediment exported at the catchment scale. Such a small spatial unit approach neglects the transfer of sediment through catchments as well as the scale-dependency of erosion processes. Furthermore, this approach does not consider important off-site impacts of soil erosion, such as sediment deposition in reservoirs, flooding as well as ecological impacts.This study aims to illustrate the importance of also considering catchment sediment yield (SY, tkm-2y-1) in desertification assessment studies. Based on recently established databases of SY and soil loss rates in Europe and examples from previous studies, we illustrate that soil erosion rates at the plot scale are not representative for catchment SY, as they are often several orders of magnitude smaller. Also, the erosion response of catchments to changes in land use or climate often differs strongly from responses to those changes at the plot scale. We further discuss several of the impacts of SY and their link with desertification: i.e. the sedimentation of reservoirs, problems related to flooding, catchment hydrology, export of nutrients and ecological implications.Using earlier established criteria we evaluate the potential for using catchment SY as a desertification indicator and conclude that this could give an important added value to desertification studies. SY, used in combination with other indicators, allows the identification of other sediment sources than those considered at the plot scale and can reflect the results of desertification processes over longer time periods than periods over which assessments at the plot scale have been made. We argue therefore, that SY is a strong complementary indicator of desertification providing valuable information on the catchment response to changes in drivers of desertification. © 2011 Elsevier B.V

Effects of land use on annual runoff and soil loss in Europe and the Mediterranean: A meta-analysis of plot data

peer reviewedThe largest currently compiled database of plot runoff and soil loss data in Europe and the Mediterranean was analysed to investigate effects of land use on annual soil loss (SL), annual runoff (R) and annual runoff coefficient (RC). This database comprises 227 plot-measuring sites in Europe and the Mediterranean, with SL for 1056 plots (PL) representing 7024 plot-years (PY) and R for 804 PL representing 5327 PY. Despite large data variability, continental-wide trends are observed. Construction sites have the highest mean annual RC (57%) and SL (325 Mg.ha -1.yr -1). Bare soil, vineyards and tree crops have high mean annual RC (5-10%) and SL (10-20 Mg.ha -1.yr -1). Cropland and fallow show similar mean annual RC (8.0 and 7.3%), but lower SL (6.5 and 5.8 Mg.ha -1.yr -1). Plots with (semi-)natural vegetation cover show lowest mean annual RC ( 500 mm.yr -1. For shrubland, annual SL was found to decrease for P > 250-500 mm.yr -1, which is attributed to an accompanying increase in vegetation cover. However, no such trend was found for R. The results allow a rapid assessment of the impact of land-use changes on annual R, RC and SL, based on field-measured plot data. © The Author(s) 2012

Sediment yield in Europe: Regional differences in scale dependence

peer reviewedCurrent understanding of the regional variation in sediment yield (SY) and its scale dependence is limited for Europe. Based on an extensive literature review, a SY-database was assembled to bridge this gap. Measured SY-data from 1794 different locations throughout Europe were collected, representing a minimum of 29 203 catchment-years of records and comprising a wide range of catchment areas (0.01 km2 to 1 360 000 km2). Clear differences were observed between the temperate regions of Europe (low SY-values, i.e. 300 t km-2 year-1). Furthermore, for most temperate regions a negative relationship was found between catchment area and SY. For mountainous and Mediterranean regions, this was generally not the case. A comparison of catchment SY with rates of sheet and rill erosion also points to clear regional differences. Whereas soil erosion rates are generally higher than SY for temperate regions, this is not the case for the Mediterranean region. This indicates the importance of other erosion processes (i.e. landslides, riverbank erosion, and gullies). The results illustrate important regional differences in the scale dependence of SY and emphasize the need for an integrated modelling approach considering various types of sediment source and sink. Copyright © 2010 IAHS Press

A comparison of measured catchment sediment yields with measured and predicted hillslope erosion rates in Europe

Purpose: This study aims to understand better the relationship between measured soil loss rates due to sheet and rill erosion (SL), predicted SL rates and measured catchment sediment yields (SY) in Europe. Materials and methods: Analyses were based on a recently established database of measured annual SY for 1794 catchments, a database of 777 annual SL rates measured on runoff plots and two recent maps of predicted sheet and rill erosion rates in Europe (i. e. one based on empirical extrapolations of measured SL data and one based on the PESERA model). To identify regional trends, all data were grouped into eight climatic zones. Results and discussion: Measured SL rates are generally a factor of five to ten times larger than predicted SL rates and are strongly biased towards erosion-prone situations in terms of land use. Also measured SY are generally higher than predicted SL rates, especially in the Mediterranean and Alpine regions where SY is generally ten times higher than predicted SL rates. This illustrates the importance of other erosion processes contributing to SY. Regional differences in the importance of these processes and their implications are discussed. Conclusions: This study confirms previous findings indicating the relatively low sheet and rill erosion rates compared to SY in the Mediterranean region and illustrates the importance of other erosion processes contributing to SY in most regions of Europe. This indicates that hillslope erosion rates cannot be used directly to estimate SY, and consequently soil conservation programmes should focus more on the dominant erosion processes in each catchment. © 2012 Springer-Verlag

Flanders:Regional organization of water and drought and using data as driver for change

This chapter presents a summary of the analysis results of the governance of drought-related issues in the Flanders region of Belgium. In the context of the Interreg IV-B project DROP, a team of researchers from four universities and knowledge institutes visited Flanders twice to perform interviews with authorities and stakeholders (October 2013 and May 2014). The visit was supported by colleagues at the Flemish Environment Agency (Vlaamse Milieumaatschappij, VMM). The exchange was held in the form of individual and group interviews and workshops with stakeholders including representatives from different institutions and sectors, e.g. from the drinking water company, national and local nature protection organizations, local farmers and local and national farmers organizations, the Flemish Environment Agency, different provinces, e.g. Province Vlaams-Brabant, and local municipalities, e.g. Kortemark Municipality. The analysis was guided by the drought-related Governance Assessment Tool (GAT) developed for the projec