Flood frequency analysis of historical flood data under stationary and non-stationary modelling

Historical records are an important source of information on extreme and rare floods and fundamental to establish a reliable flood return frequency. The use of long historical records for flood frequency analysis brings in the question of flood stationarity, since climatic and land-use conditions can affect the relevance of past flooding as a predictor of future flooding. In this paper, a detailed 400 yr flood record from the Tagus River in Aranjuez (central Spain) was analysed under stationary and non-stationary flood frequency approaches, to assess their contribution within hazard studies. Historical flood records in Aranjuez were obtained from documents (Proceedings of the City Council, diaries, chronicles, memoirs, etc.), epigraphic marks, and indirect historical sources and reports. The water levels associated with different floods (derived from descriptions or epigraphic marks) were computed into discharge values using a one-dimensional hydraulic model. Secular variations in flood magnitude and frequency, found to respond to climate and environmental drivers, showed a good correlation between high values of historical flood discharges and a negative mode of the North Atlantic Oscillation (NAO) index. Over the systematic gauge record (1913–2008), an abrupt change on flood magnitude was produced in 1957 due to constructions of three major reservoirs in the Tagus headwaters (Bolarque, Entrepeñas and Buendia) controlling 80% of the watershed surface draining to Aranjuez. Two different models were used for the flood frequency analysis: (a) a stationary model estimating statistical distributions incorporating imprecise and categorical data based on maximum likelihood estimators, and (b) a time-varying model based on "generalized additive models for location, scale and shape" (GAMLSS) modelling, which incorporates external covariates related to climate variability (NAO index) and catchment hydrology factors (in this paper a reservoir index; RI). Flood frequency analysis using documentary data (plus gauged records) improved the estimates of the probabilities of rare floods (return intervals of 100 yr and higher). Under non-stationary modelling flood occurrence associated with an exceedance probability of 0.01 (i.e. return period of 100 yr) has changed over the last 500 yr due to decadal and multi-decadal variability of the NAO. Yet, frequency analysis under stationary models was successful in providing an average discharge around which value flood quantiles estimated by non-stationary models fluctuate through time

Caracterización tecnológica de las explotaciones ovinas y caprinas en los departamentos de la Guajira, César y Magdalena

Durante 4 años consecutivos (1990-1994) se llevó a cabo el presenta trabajo con el objetivo de caracterizar los sistemas de producción de ovinos de pelo y caprinos. Por medio de la metodología de estudio de casos se estimaron los parámetros productivos y reproductivos en 16 explotaciiones de los departamentos de La Guajira, Cesar y Magdalena, los aspectos socioeconómicos se tomaron de resultados de 159 encuestas realizadas en 93 veredas ubicadas en las 4 subregiones seleccionadas. El sistema está localizado en pisos térmicos cálido árido (18 por ciento) y cálido subhúmedo (49.1 por ciento). Se identificaron los subsistemas caprinos asociados a ovinos, ovinos asociados a caprinos y bovinos asociados a ovinos. Predomina el sistemas de explotación tradicional, extensivo (90.4 por ciento), de manejo simple, siendo el objetivo la venta de animales en pie (64.1 por ciento) autoconsumo (32.1 por ciento) y venta de leche (3.8 por ciento). La falta de asistencia técnica (31.2 por ciento), la inseguridad (17.1 por ciento) y la falta de crédito (17.1 por ciento) fueron señaladas como los principales limitantes. La prolificidad obtenida para ambas especies fue mayor de 1.40.Caprinos-Capra hircu

Global burden and strength of evidence for 88 risk factors in 204 countries and 811 subnational locations, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

Background: Understanding the health consequences associated with exposure to risk factors is necessary to inform public health policy and practice. To systematically quantify the contributions of risk factor exposures to specific health outcomes, the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 aims to provide comprehensive estimates of exposure levels, relative health risks, and attributable burden of disease for 88 risk factors in 204 countries and territories and 811 subnational locations, from 1990 to 2021. Methods: The GBD 2021 risk factor analysis used data from 54 561 total distinct sources to produce epidemiological estimates for 88 risk factors and their associated health outcomes for a total of 631 risk–outcome pairs. Pairs were included on the basis of data-driven determination of a risk–outcome association. Age-sex-location-year-specific estimates were generated at global, regional, and national levels. Our approach followed the comparative risk assessment framework predicated on a causal web of hierarchically organised, potentially combinative, modifiable risks. Relative risks (RRs) of a given outcome occurring as a function of risk factor exposure were estimated separately for each risk–outcome pair, and summary exposure values (SEVs), representing risk-weighted exposure prevalence, and theoretical minimum risk exposure levels (TMRELs) were estimated for each risk factor. These estimates were used to calculate the population attributable fraction (PAF; ie, the proportional change in health risk that would occur if exposure to a risk factor were reduced to the TMREL). The product of PAFs and disease burden associated with a given outcome, measured in disability-adjusted life-years (DALYs), yielded measures of attributable burden (ie, the proportion of total disease burden attributable to a particular risk factor or combination of risk factors). Adjustments for mediation were applied to account for relationships involving risk factors that act indirectly on outcomes via intermediate risks. Attributable burden estimates were stratified by Socio-demographic Index (SDI) quintile and presented as counts, age-standardised rates, and rankings. To complement estimates of RR and attributable burden, newly developed burden of proof risk function (BPRF) methods were applied to yield supplementary, conservative interpretations of risk–outcome associations based on the consistency of underlying evidence, accounting for unexplained heterogeneity between input data from different studies. Estimates reported represent the mean value across 500 draws from the estimate's distribution, with 95% uncertainty intervals (UIs) calculated as the 2·5th and 97·5th percentile values across the draws. Findings: Among the specific risk factors analysed for this study, particulate matter air pollution was the leading contributor to the global disease burden in 2021, contributing 8·0% (95% UI 6·7–9·4) of total DALYs, followed by high systolic blood pressure (SBP; 7·8% [6·4–9·2]), smoking (5·7% [4·7–6·8]), low birthweight and short gestation (5·6% [4·8–6·3]), and high fasting plasma glucose (FPG; 5·4% [4·8–6·0]). For younger demographics (ie, those aged 0–4 years and 5–14 years), risks such as low birthweight and short gestation and unsafe water, sanitation, and handwashing (WaSH) were among the leading risk factors, while for older age groups, metabolic risks such as high SBP, high body-mass index (BMI), high FPG, and high LDL cholesterol had a greater impact. From 2000 to 2021, there was an observable shift in global health challenges, marked by a decline in the number of all-age DALYs broadly attributable to behavioural risks (decrease of 20·7% [13·9–27·7]) and environmental and occupational risks (decrease of 22·0% [15·5–28·8]), coupled with a 49·4% (42·3–56·9) increase in DALYs attributable to metabolic risks, all reflecting ageing populations and changing lifestyles on a global scale. Age-standardised global DALY rates attributable to high BMI and high FPG rose considerably (15·7% [9·9–21·7] for high BMI and 7·9% [3·3–12·9] for high FPG) over this period, with exposure to these risks increasing annually at rates of 1·8% (1·6–1·9) for high BMI and 1·3% (1·1–1·5) for high FPG. By contrast, the global risk-attributable burden and exposure to many other risk factors declined, notably for risks such as child growth failure and unsafe water source, with age-standardised attributable DALYs decreasing by 71·5% (64·4–78·8) for child growth failure and 66·3% (60·2–72·0) for unsafe water source. We separated risk factors into three groups according to trajectory over time: those with a decreasing attributable burden, due largely to declining risk exposure (eg, diet high in trans-fat and household air pollution) but also to proportionally smaller child and youth populations (eg, child and maternal malnutrition); those for which the burden increased moderately in spite of declining risk exposure, due largely to population ageing (eg, smoking); and those for which the burden increased considerably due to both increasing risk exposure and population ageing (eg, ambient particulate matter air pollution, high BMI, high FPG, and high SBP). Interpretation: Substantial progress has been made in reducing the global disease burden attributable to a range of risk factors, particularly those related to maternal and child health, WaSH, and household air pollution. Maintaining efforts to minimise the impact of these risk factors, especially in low SDI locations, is necessary to sustain progress. Successes in moderating the smoking-related burden by reducing risk exposure highlight the need to advance policies that reduce exposure to other leading risk factors such as ambient particulate matter air pollution and high SBP. Troubling increases in high FPG, high BMI, and other risk factors related to obesity and metabolic syndrome indicate an urgent need to identify and implement interventions. Funding: Bill & Melinda Gates Foundation

Vulnerability Assessment with Scarce Information for a Quantitative Flood Risk Model. Case Study Monteria-Colombia

A quantitative flood risk assessment requires that vulnerability and hazard be evaluated quantitatively as well. In our research, we assess the flood risk of a south-east suburb of the city of Montería Colombia. We proposed to assess vulnerability through damage functions development and their incorporation in the flood risk assessment. Risk is quantifying as expected annual economic loss. Vulnerability is estimated based on the relationship between the physical condition and the contents of the households, with their ability to resist flooding. Flood damages in movable property, structures and public areas were stablished through depth-damage functions. Data for construction of these depth damage functions were obtained through a survey and field observations of the entire selected area. In order to identify damage, we have taken advantage of the recent memory of the communities regarding their perception of real damages during a flood occurred in July 2010. Structural elements and movable assets were classified in categories and people were asked about damage in these categories. Additionally, the water marks on walls, doors and other structural elements were identified. In order to quantify hazard, we calibrate a simple hydrological model and a hydraulic model, based in the records and water marks left by the July 2010 flood. A quantitative risk model was applied that incorporates the quantitative risk and vulnerability estimation. Depth-damage functions developed are a useful tool that can be used in other regions in Colombia and Caribbean with similar socioeconomic and climatic conditions. Results shown that it is possible to typify the houses and the movable property by means of the construction of functions and it is possible to obtain the quantitative risk, contributing a practical tool for the urban planning of this zone of the city. © 2019 Published under licence by IOP Publishing Ltd

Probable Maximum Flood estimation using upper bounded statistical models and its effect on high return period quantiles

This work proposes the estimation of high return period quantiles using upper bounded distribution functions, assuming its upper bound parameter as a statistical estimator of the PMF. It is proposed also to use additional Non-Systematic information in order to reduce the estimation uncertainty of high return period quantiles and the Probable Maximum Flood. Three upper bounded cumulative probability distribution functions were applied to some Mediterranean rivers in Spain. Depending on the information scenario, different methods to estimate the upper limit of these distribution functions have been merged with the Maximum Likelihood method. Results show that it is possible to obtain a statistical estimate of the Probable Maximum Flood value and to establish its associated uncertainty. With enough information, the associated estimation uncertainty for very high return period quantiles is considered acceptable, even for the PMF estimate. © 2012 Taylor & Francis Group

Effect of population dynamics and land use on the contribution of sediments to reservoirs for hydropower generation

Sediment load in reservoirs causes loss of reservoir storage and reduces its usable life. There are management strategies focused in sediment removal or reducing trapping in reservoirs, and there are basin management strategies oriented to reduce sediment production and load reaching reservoirs. In a social and political moment, like the present time in Colombia, rural return migration is expected. Ex-ante evaluation of strategies to reducing sediment production is required, in order to implement them previously and avoid the acceleration of the reduction of the usable life of reservoirs. This paper presents the assessment of the impact on sediment production in a basin according to different land use planning strategies, in the context of the rural population dynamics expected in the coming years in Colombia. The San Carlos River basin contributes to a reservoir for hydropower generation, which currently generates the major percentage of hydropower energy in the power generation matrix of Colombia. We implemented on the basin the TETIS model, a distributed conceptual hydrological and sediment model. This model allows to estimate sediment production, through simulation of solid discharge series at anywhere in the basin. The TETIS sedimentological submodel was calibrated and validated using reservoir sedimentation volumes as an estimator of the total sediment transport. Different strategies and alternatives for land use were established, including lack of planning and agricultural policies. Results show an increase in the sediment production in the long term, if a policy on the adequate use of the soil is not implemented. The results allow to define the strategic zones of the basin where the efforts for the implementation of good agricultural practices, reforestation and soil conservation must be focused. © 2018 Oxford University Press. All rights reserved

Effect of sediment management decision on a hydropower plant value [Incidencia de la decisión de manejo de sedimentos en el valor de una central hidroeléctrica]

Sedimentation reduces the useful life of reservoirs and the value of hydropower plants. The aim is to determine the effect of sediment management decisions on the value of a plant. First, management alternatives are ranked with the AHP technique according to the perception of six experts. Second, the plant is valued by cash flow (FCL) and RESCON 2 BETA (RES). Results shows three alternatives ranked: reforestation, agriculture and dam construction. The useful life of reservoir increases in 84% (reforestation), 40% (agriculture), and 76% (dam). The value of the plant increases in 21% (FCL) and 21.74% (RES) for reforestation, 11.59% (FCL) and 13.18% (RES) for agriculture, and 20.07% (FCL) and 19.93% (RES) for dam building. It is concluded that sediment management affects the value of the plant since the useful life of the reservoir affects the value of continuity. © The author; licensee Universidad Nacional de Colombia

Hydrological response of a dryland ephemeral river to southern African climatic variability during the last millennium

A long-term flood record from the Buffels River, the largest ephemeral river of NW South Africa (9250 km2), was reconstructed based on interpretation of palaeoflood, documentary and instrumental rainfall data. Palaeoflood data were obtained at three study reaches, with preserved sedimentary evidence indicating at least 25 large floods during the last 700yr. Geochronological control for the palaeoflood record was provided by radiocarbon and optically stimulated luminescence (OSL) dating. Annual resolution was obtained since the 19th century using the overlapping documentary and instrumental records. Large floods coincided in the past within three main hydroclimatic settings: (1) periods of regular large flood occurrence (1 large flood/~30yr) under wetter and cooler prevailing climatic conditions (AD 1600-1800), (2) decreasing occurrence of large floods (1 large flood/~100yr) during warmer conditions (e.g., AD 1425-1600 and after 1925), and (3) periods of high frequency of large floods (~4-5 large floods in 20-30yr) coinciding with wetter conditions of decadal duration, namely at AD 1390-1425, 1800-1825 and 1915-1925. These decadal-scale periods of the highest flood frequency seem to correspond in time with changes in atmospheric circulation patterns, as inferred when comparing their onset and distribution with temperature proxies in southern Africa. © 2011 University of Washington

PCR with Paracoccidioides brasiliensis specific primers: potential use in ecological studies PCR com «primers» específicos de Paracoccidioides brasiliensis: uso potencial em estudos ecológicos

The precise microenvironment of Paracoccidioides brasiliensis has not yet been discovered perhaps because the methods used are not sensitive enough. We applied to this purpose the polymerase chain reaction (PCR) using three sets of specific primers corresponding to two P. brasiliensis genes. This fungus as well as several other fungi, were grown and their DNA obtained by mechanical disruption and a phenol chloroform isoamylalcohol-based purification method. The DNA served for a PCR reaction that employed specific primers from two P. brasiliensis genes that codify for antigenic proteins, namely, the 27 kDa and the 43 kDa. The lowest detection range for the 27 kDa gene was 3 pg. The amplification for both genes was positive only with DNA from P. brasiliensis; additionally, the mRNA for the 27 kDa gene was present only in P. brasiliensis, as indicated by the Northern analysis. The standardization of PCR technology permitted the amplification of P. brasiliensis DNA in artificially contaminated soils and in tissues of armadillos naturally infected with the fungus. These results indicate that PCR technology could play an important role in the search for P. brasiliensis’ habitat and could also be used in other ecological studies.<br>O microambiente adequado do Paracoccidioides brasiliensis não foi ainda bem esclarecido, talvez porque os métodos utilizados não sejam suficientemente sensíveis. Aplicamos com este propósito, a reação em cadeia da polimerase (PCR) usando três jogos de primers específicos do P. brasiliensis, correspondendo a dois dos genes do P. brasiliensis. Este fungo, assim como outros fungos, foram cultivados e seus DNAs obtidos por ruptura mecânica e purificados com mistura de fenol-clorofórmio com álcool isoamílico. Os DNAs serviram para a reação de PCR utilizando-se primers específicos para dois dos genes do P. brasiliensis que codificam para as proteínas antigênicas, denominadas, 27 kDa e 43 kDa. O limite mínimo de detecção para o gene 27 kDa foi de 3 pg. A amplificação para os dois genes foi positiva só com o DNA do P. brasiliensis; além disso, o mRNA para o gene de 27kDa estava presente apenas no material do P. brasiliensis, como mostrado pela análise por Northern-blot. A padronização da técnica do PCR permitiu a amplificação do DNA do P. brasiliensis em solos contaminados artificialmente com o fungo e em tecidos de tatus infectados na natureza. Estes resultados indicam que a técnica do PCR podería ter um papel muito importante na pesquisa do habitat do P. brasiliensis e, além disso, podería ser utilizada em outros estudos ecológicos