In meeting water demand, many aquifers have been over-exploited by pumping in excess of recharge, leading to significant groundwater level decline and seawater intrusion in coastal areas. Water resources availability is going to be of the most important problems to face in the decades to come. To meet the growing water demand and also in response to water scarcity, measures to regulate demand and to increase supplies from new sources have been promoted. Among
the policies to be cited, recycling and reuse of treated wastewater (TWW) is gaining popularity due to: the constantly improving quality of TWW discharges in line with increasing technology, and the need of non-conventional water sources in the context of integrated water resources management (IWRM) to meet the water demand. Over the last decade there has been significant growth in the application of reuse, important advances in reuse technologies, and an increase in the number of states that have implemented either rules or guidelines for reuse EPA,2012; BOE, 2007). The two water reuse options currently gaining prevalence, direct potable reuse (DPR, defined through an integrated planning process) and indirect potable reuse (IPR, are considered as part of the water cycle increasing water resources, improving the IWRM and supply security. Agricultural irrigation and recreational facilities (ex. golf courses) and aquifer recharge (MAR) may be one the most well-known applications of reclaimed water. Successes, possible effects in groundwater and lessons learned are presented through specific case studies (De Bustamante et al., 2010; Candela et al; 2007; Candela et al., 2016; Teijón et al., 2016).
Monitoring total bromine and bromide concentrations in soils is significant in many environmental studies. Thus fast analytical methodologies that entail simple sample preparation and low-cost analyses are desired.; In the present work, the possibilities and drawbacks of low-power total reflection X-ray fluorescence spectrometry (TXRF) for the determination of total bromine and bromide contents in soils" were evaluated.; The direct analysis of a solid suspension using 20 mg of fine ground soil (<63 mu m) gave a 3.7 mg kg(-1) limit of detection for bromine which, in most cases, was suitable for monitoring total bromine content in soils (Br content range in soils = 5-40 mg kg(-1)). Information about bromide determination in soils is also possible by analyzing the Br content in water soil extracts. In this case, the TXRF analysis can be directly performed by depositing 10 mu L of the internal standardized soil extract sample on a quartz glass reflector in a measuring time of 1500 s. The bromide limit of detection by this approach was 10 mu g L-1.; Good agreement was obtained between the TXRF results for the total bromine and bromide determinations in soils and those obtained by other popular analytical techniques, e.g. energy dispersive X-ray fluorescence spectrometry (total bromine) and ionic chromatography (bromide).; As a study case, the TXRF method was applied to study bromine accumulation in two agricultural soils fumigated with a methyl bromide pesticide and irrigated with regenerated waste water. (C) 2016 Elsevier Ltd. All rights reserved.
Monitoring total bromine and bromide concentrations in soils is significant in many environmental studies. Thus fast analytical methodologies that entail simple sample preparation and low-cost analyses are desired. In the present work, the possibilities and drawbacks of low-power total reflection X-ray fluorescence spectrometry (TXRF) for the determination of total bromine and bromide contents in soils were evaluated. The direct analysis of a solid suspension using 20 mg of fine ground soil (<63 µm) gave a 3.7 mg kg-1 limit of detection for bromine which, in most cases, was suitable for monitoring total bromine content in soils (Br content range in soils = 5-40 mg kg-1). Information about bromide determination in soils is also possible by analyzing the Br content in water soil extracts. In this case, the TXRF analysis can be directly performed by depositing 10 µL of the internal standardized soil extract sample on a quartz glass reflector in a measuring time of 1500 s. The bromide limit of detection by this approach was 10 µg L-1. Good agreement was obtained between the TXRF results for the total bromine and bromide determinations in soils and those obtained by other popular analytical techniques, e.g. energy dispersive X-ray fluorescence spectrometry (total bromine) and ionic chromatography (bromide). As a study case, the TXRF method was applied to study bromine accumulation in two agricultural soils fumigated with a methyl bromide pesticide and irrigated with regenerated waste water.
Climate change impact on water resources (streamflow and deep natural recharge) based on the downscaled outputs from the ECHAM5 general circulation model (GCM) has been investigated in the Mediterranean basin (Fluvia, Spain) for the A2, B1 greenhouse scenarios and 2000-2024/2025-2050 time slices. The HEC-HMS 3.4 rainfall-runoff numerical model was the basic tool used to generate streamflow for the historical period, and deep natural recharge was calculated from Visual-BALAN 2.0, a water-soil-plant distributed model. The hydrologic and recharge models were employed to generate future climate change hydrographs and the deep recharge amount. Furthermore, the selected future climate scenarios, subject to possible changes in the land use/land cover forecast, were integrated into the models, and water resource impacts were assessed. The multiple combinations of climate model, time slices, greenhouse scenarios, land use/land cover scenarios and hydrological estimation methods resulted in six scenarios. The obtained results estimate an increase in temperature (1.5 degrees C), a decline in precipitation (17%) and a maximum decrease of 49.5% and 16.8% in runoff and groundwater recharge, respectively, for 2050 (A2) compared to the historical values. Planned land cover scenarios, implying small changes of agricultural and forested land, show no major contribution to future water resource changes. According to the results, the most sensitive parameters conditioning future water resources are changes in temperature and precipitation.
Climate change impact on water resources (streamflow and deep natural recharge) based on the downscaled outputs from the ECHAM5 general circulation model (GCM) has been investigated in the Mediterranean basin (Fluvià, Spain) for the A2, B1 greenhouse scenarios and 2000–2024/2025–2050 time slices. The HEC-HMS 3.4 rainfall-runoff numerical model was the basic tool used to generate streamflow for the historical period, and deep natural recharge was calculated from Visual-BALAN 2.0, a water-soil-plant distributed model. The hydrologic and recharge models were employed to generate future climate change hydrographs and the deep recharge amount.
Furthermore, the selected future climate scenarios, subject to possible changes in the land use/land cover forecast, were integrated into the models, and water resource impacts were assessed. The multiple combinations of climate model, time slices, greenhouse scenarios, land use/land cover scenarios and hydrological estimation methods resulted in six scenarios. The obtained results estimate an increase in temperature (1.5 C), a decline in precipitation (17%) and a maximum decrease of 49.5% and 16.8% in runoff and groundwater recharge, respectively, for 2050 (A2) compared to the historical values. Planned land cover scenarios, implying small changes of agricultural and forested land, show no major contribution to future water resource changes. According to the results, the most sensitive parameters conditioning future water resources are changes in temperature and precipitation.
A screening survey of 81 pharmaceuticals was carried out at a wastewater facility and in a detrital aquifer (Barcelona, Spain), where treated wastewater (TWW) was injected through wells to build up a hydraulic barrier against seawater intrusion. The monitored data correspond to the 2007–2010 period. The TWW was tertiary treated with additional treatment consisting of ultrafiltration, reverse osmosis and UV disinfection. During the monitoring period groundwater monitoring was carried out in wells located within a 1-km radius distance from the injection wells. During monitoring period 20 new pharmaceuticals were detected in the aquifer media and 11 compounds were found with concentration above 0.1 µg l-1 (selected threshold) in both TWW and wells. After 1 year of TWW injection change of redox conditions, a decrease of Cl- concentration and presence of 11 pharmaceuticals (4-AAA, 4-FAA, carbamazepine, ciprofloxacin, diazepam, diclofenac, hydrochlorothiazide, mepivacaine, sulfamethoxazole, sulfamethazine and sulfapyridine) was observed in the monitoring wells. After the studied period the sodium-chloride aquifer water type evolved to a bicarbonate-sulphate facies. Decrease of the pharmaceuticals concentration in groundwater appears to be driven by the dilution process and hydraulic characteristics of the aquifer media, with the attenuation or degradation process much less important.
The final publication is available at Springer via http://dx.doi.org/10.1007/s12665-015-4956-8
The naturally high microbiological and chemical quality of groundwater, captured at springheads and in shallow galleries and dugwells, has been vital for human survival, wellbeing and development from our earliest history – and remains so today. The purity of groundwater, coupled with its mineral content, is such that many springs historically have been attributed medicinal value.
Strategic overview series of the International Association of Hydrogeologists-IAH. This Series is designed both to inform professionals in other sectors of key interactions with groundwater resources and hydrogeological science, and to guide IAH members in their outreach to related sectors.
Páez, G.; Muñoz, F.; Candela, L.; Tamoh, K.; Valdes-Abellan, J. Science of the total environment Vol. 539, p. 410-419 DOI: 10.1016/j.scitotenv.2015.08.153 Data de publicació: 2016-01 Article en revista
Extensive application of vinasse, a subproduct from sugar cane plantations for bioethanol production, is currently taking place as a source of nutrients that forms part of agricultural management in different agroclimatic regions. Liquid vinasse composition is characterised by high variability of organic compounds and major ions, acid pH (4.7), high TDS concentration (117,416-599,400 mg L-1) and elevated EC (14,350-64,099 ¿S cm-1). A large-scale sugar cane field application is taking place in Valle del Cauca (Colombia), where monitoring of soil, unsaturated zone and the aquifer underneath has been made since 2006 to evaluate possible impacts on three experimental plots. For this assessment, monitoring wells and piezometers were installed to determine groundwater flow and water samples were collected for chemical analysis. In the unsaturated zone, tensiometers were installed at different depths to determine flow patterns, while suction lysimeters were used for water samples chemical determinations. The findings show that in the sandy loam plot (Hacienda Real), the unsaturated zone is characterised by low water retention, showing a high transport capacity, while the other two plots of silty composition presented temporal saturation due to La Niña event (2010-2011). The strong La Niña effect on aquifer recharge which would dilute the infiltrated water during the monitoring period and, on the other hand dissolution of possible precipitated salts bringing them back into solution may occur. A slight increase in the concentration of major ions was observed in groundwater (~5% of TDS), which can be attributed to a combination of factors: vinasse dilution produced by water input and hydrochemical processes along with nutrients removal produced by sugar cane uptake. This fact may make the aquifer vulnerable to contamination.
Irrigation with slightly saline water is becoming a normal practice in water-scarce regions to increase the available water resources. Although in many areas its use has been proved sustainable, assessment of possible longterm impacts due to its application are scarce due to lack of real field experiences. To overcome this barrier,
numerical simulation of variable-saturated flow and reactive transport is an efficient tool to assess the long-term irrigation impacts on soil and aquifer caused by non-conventional water use. A multicomponent reactive transport model, HP1, to simulate long term salt leaching to groundwater has been applied to an experimental site developed in a semi-arid region (SE Spain). The model is based on a previously
validated and calibrated flow model based on several years of observation data: soil pressure head (at 20 and 60 cm depth) and volumetric water content (at 20, 40, 60, 90 and 120 cm depth). Aquifer media dispersivity for the reactive model was obtained from a field tracer test and inverse modelling. Among the obtained results processes related to salt dynamics in the non-saturated zone of the aquifer, and accumulative waterborne salt recharge under different agricultural and water management strategies are shown.
Vadillo Pérez, I.; Candela, L.; Gambero-Sedeño, L.; Urresti-Estala, B.; Jiménez-Gavilán, P.; Corada-Fernández, C. International Association Hydrogeologists Congress p. 370 Data de presentació: 2015-09 Presentació treball a congrés
This research is focused in the Guadalhorce porous aquifer (Malaga, south of Spain), to study the distribution of EC and the interaction with the hydrogeochemistry. 14 EC (Ibuprofen, Hydrochlorothiazide, Salicilic Acid, Triclosan, Menfenamic Acid, Carbamazepine, Trimethoprim, Ofloxacin, Cafeine, Metotrexato, Metronidazole, Sulfadiazine,
Sulfamethazine and Sulfamethoxazole) and 36 paramaters including electrical conductivity, T, pH, DO, major ions (Cl-, SO42-, HCO3-, NO3-, Ca2+, Mg2+, Na+, K+), metals (B, Al, Fe, Mn, Cd, Pb, Zn, As and Se) and isotopes (d2H-H2O, d18O-H2O, d34S-SO42-) were controlled in a single field sampling (June 2012). Relationships between certain
pollutants by its focus of origin are studied.
Since the 1960's the coastal aquifer overlying the irrigated plain of Korba El Mida (East coast of Cap-Bon) has been under intensive exploitation leading to groundwater degradation quality by seawater intrusion and irrigation return flow. Also, the main coastal sabkhas (wetlands) are no longer the natural outlets of the aquifer, due to a
reversal of the hydraulic gradient jointly with groundwater depletion. Since 1962 geophysical surveys, use of environmental isotopes and tracers, and groundwater monitoring campaigns for sampling and level measurements of existing piezometers and surrounding wells, have been carried out in order to assess origin of salinity, extent and evolution along time. Since 2008, artificial recharge groundwater with reclaimed water through three infiltration basins is taking place to increase groundwater resources, restore the piezometric levels, and improve water quality. Values of Electric Conductivity may range between 0.3 and 10.6 dS/m in the surroundings of Korba and El Mida;
most piezometers and some wells had essentially sodium-chloride facies but some wells present a calcium-sulfate facies. High nitrate concentration (up to 300 mg/L), potassium and sulphate increase due to mineral fertilizers and manure application are observed in some areas of the aquifer, fact supported by the Cl-NO3 diagrams. The high
heterogeneity of the salinity distribution, due to geological and hydrodynamic conditions, generates complex groundwater mixing of different origins: seawater intrusion, irrigation return flow, natural recharge besides the existing induced aquifer recharge in the area. The spatial variability of concentrations in the Korba-El Mida aquifer
reveals the complexity of the groundwater contamination by salinization and anthropogenic activities.
Irrigated agriculture is usually performed in semi-arid regions despite scarcity of water resources. Therefore, optimal irrigation management by monitoring the soil is essential, and assessing soil hydraulic properties and water flow dynamics is presented as a first measure. For this purpose, the control of volumetric water content, ¿, and pressure head, h, is required. This study adopted two types of monitoring strategies in the same experimental plot to control ¿ and h in the vadose zone: i) non-automatic and more time-consuming; ii) automatic connected to a datalogger. Water flux was modelled with Hydrus-1D using the data collected from both acquisition strategies independently (3820 daily values for the automatic; less than 1000 for the non-automatic). Goodness-of-fit results reported a better adjustment in case of automatic sensors. Both model outputs adequately predicted the general trend of ¿ and h, but with slight differences in computed annual drainage (711 mm and 774 mm). Soil hydraulic properties were inversely estimated from both data acquisition systems. Major differences were obtained in the saturated volumetric water content, ¿s, and the n and a van Genuchten model shape parameters. Saturated hydraulic conductivity, Ks, shown lower variability with a coefficient of variation range from 0.13 to 0.24 for the soil layers defined. Soil hydraulic properties were better assessed through automatic data acquisition as data variability was lower and accuracy was higher.
Candela, L.; Tamoh, K.; Olivares, G.; Gomez, M.; Valdes-Abellan, J. Aqua-LAC: revista del Programa Hidrológico Internacional para América Latina y el Caribe Vol. 7, num. 13, p. 1-10 Data de publicació: 2015-03 Article en revista
Se presentan los efectos del cambio global en la cuenca del río Tordera (España) para el periodo 2000-2050, escenarios climáticos A2 (medio-alto) definidos por el Panel Intergubernamental del Cambio Climático (IPCC, 200) y escenarios socioeconómicos (cambios previstos en la cuenca) denominados estable y tendencial. Los efectos sobre los recursos hídricos se han analizado de forma conjunta superficial-subterránea mediante una metodológica de tipo acoplado. Para establecer los impactos futuros sobre los recursos hídricos se ha seleccionado el Modelo de Circulación Global ECHAM5 (Max Planck Institute). Los resultados obtenidos indican una disminución de la precipitación del 11.3% y un aumento de la temperatura de 1ºC, respecto a los valores históricos de la zona. De acuerdo a la proyección futura (2050) sobre cambios en los recursos hídricos, la escorrentía superficial obtenida mediante simulación con el código HEC-HMS 3.4 experimenta una reducción del 31.8% respecto al valor histórico y la recarga natural, estimada mediante VISUAL-Balan, se reduce en un 11.7%. El balance en el acuífero deltaico simulado mediante MODFLOW 2009.1 Pro muestra igualmente una disminución de los parámetros del balance. Los cambios del uso del suelo previstos de acuerdo a la legislación vigente (escenarios socioeconómicos) no conducen a la generación de un impacto apreciable en los recursos hídricos; según los escenarios definidos la variación de precipitación y temperatura son los parámetros fundamentales del cambio previsto.
Corada-Fernández, C.; Jiménez, J.; Candela, L.; González-Mazo, E.; Lara-Martín, P. Chemosphere Vol. 119, num. Supplement, p. S131-S137 DOI: 10.1016/j.chemosphere.2014.04.098 Data de publicació: 2015-01 Article en revista
Irrigation with reclaimed water is becoming a common practice in arid- and semi-arid regions as a consequence of structural water resource scarcity. This practice can lead to contamination of the vadose zone if sewage-derived contaminants are not removed properly. In the current work, we have characterized soils from the Guadalete River basin (SW Spain), which are often irrigated with reclaimed water from a nearby wastewater treatment plant and amended using sludge. Physico-chemical, mineralogical and hydraulic properties were measured in soil samples from this area (from surface up to 2 m depth). Emerging contaminants (synthetic surfactants and pharmaceutically active compounds, or PhACs) were also determined. Synthetic surfactants, widely used in personal care products (PCPs), were found in a wide range of concentrations: 73–1300 µg kg-1 for linear alkylbenzene sulfonates (LAS), 120–496 µg kg-1 for alkyl ethoxysulfates (AES), 19–1090 µg kg-1 for alcohol polyethoxylates (AEOs), and 155–280 µg kg-1 for nonylphenol polyethoxylates (NPEOs). The presence of surfactant homologues with longer alkyl chains was predominant due to their sorption capacity. A positive correlation was found between LAS and AEOs and soil organic carbon and clay content, respectively. Out of 64 PhACs analyzed, only 7 were detected occasionally (diclofenac, metoprolol, fenofibrate, carbamazepine, clarithromycin, famotidine and hydrochlorothiazide), always at very low concentrations (from 0.1 to 1.3 µg kg-1).
To satisfy water demand in the arid climate area (SE Spain), small private desalination plants (more than 1000) of brackish groundwater are in operation. This
process has led to an increase of groundwater salinity as a consequence of aquifers connection, uncontrolled
subsurface injection of brines and pitfalls of the brines conveyor network. Measures being taken, including the
economic efficiency of the small private desalination plants with regard to groundwater, and obtained results are presented.
La caracterización de las propiedades hidráulicas del suelo es fundamental para estudios relacionados con la agronomía, hidrología y ciencias ambientales. No todos los equipos son igualmente aplicables para dichas caracterizaciones, siendo clave el conocimiento previo del tipo de suelo para elegir la técnica más adecuada. Este trabajo compara los resultados obtenidos para la determinación en laboratorio de las curvas de retención de agua del suelo, pF, y la conductividad hidráulica saturada, KS, mediante diferentes equipos. La conductividad hidráulica fue calculada con una cámara triaxial (GDS Instrument®) y con el equipo KSAT (UMS®). La curva de retención se obtuvo mediante la cámara de Richards (Soil Moisture Equipment Corp.) y el equipo HYPROP (HYdraulic PROPerty analyzer de UMS®), que mide directamente el potencial mátricial en función de la pérdida de contenido de humedad por evaporación. Los resultados obtenidos se evaluaron mediante técnicas estadísticas.
The TWAP Groundwater Component Project for the European region focuses on three subregions, defined by taking into account the similarities of water management issues by UNECE: Western and central Europe, South-Eastern Europe, Eastern and Northern Europe. The region is characterised by a great diversity in water resources availability, pressure status and responses in Transboundary Aquifers (TBA).
Teijón, G.; Candela, L.; Šimunek, J.; Tamoh, K.; Valdes-Abellan, J. Soil and sediment contamination Vol. 23, num. 7, p. 736-750 DOI: 10.1080/15320383.2014.869194 Data de publicació: 2014-10-03 Article en revista
Naproxen-C14H14O3 is a nonsteroidal anti-inflammatory drug which has been found at detectable concentrations in wastewater, surface water, and groundwater. Naproxen is relatively hydrophilic and is in anionic form at pH between 6 and 8. In this study, column experiments were performed using an unconsolidated aquifer material from an area near Barcelona (Spain) to assess transport and reaction mechanisms of Naproxen in the aquifer matrix under different pore water fluxes. Results were evaluated using HYDRUS-1D, which was used to estimate transport parameters. Batch sorption isotherms for Naproxen conformed with the linear model with a sorption coefficient of 0.42 (cm3 g-1), suggesting a low sorption affinity. Naproxen breakthrough curves (BTCs) measured in soil columns under steady-state, saturated water flow conditions displayed similar behavior, with no apparent hysteresis in sorption or dependence of retardation (R, 3.85-4.24) on pore water velocities. Soil sorption did not show any significant decrease for increasing flow rates, as observed from Naproxen recovery in the effluent. Sorption parameters estimated by the model suggest that Naproxen has a low sorption affinity to aquifer matrix. Most sorption of Naproxen occurred on the instantaneous sorption sites, with the kinetic sorption sites representing only about 10 to 40% of total sorption.
We studied the transport of a pesticide at field scale, namely carbofuran molecule which is known for its high mobility, especially in sandy soils with high hydraulic conductivity and low organic matter. To add to our knowledge of the future of this high-mobility molecule in this type of soils, we developed a mechanistic numerical model allowing the simulation of hydric and solute transfers (bromide and carbofuran) in the soil. We carried out this study in an agricultural plot in the region of Mnasra in Morocco. Confrontation of the measured and simulated values allowed the calibration of the parameters of hydric transfer and carbofuran. The developed model accurately reproduces the
Despite a weak irrigation and precipitation regime, carbofuran was practically leached beyond the root zone. Prospective simulations show that under a more important irrigation regime, carbofuran reaches 100cm depth, whereas it does not exceed 60cm under a deficit regime.
Pascual, J.; Pérez-Foguet, A.; Codony, J.; Raventós, E.; Candela, L. International journal of water resources development Vol. 30, num. 3, p. 572-587 DOI: 10.1080/07900627.2013.843410 Data de publicació: 2014-09-01 Article en revista
This article assesses the relation between water management, environmental degradation and poverty through a stakeholder analysis focused on the status and management of water resources. It draws from the situation observed in the Ethiopian Central Rift Valley, an endorheic basin south of Addis Ababa where human activities have resulted in the degradation of most freshwater ecosystems and where the vast majority of the population lives in poverty. It proposes a shift in water governance that focuses on improving economic and social welfare and enhancing environmental sustainability. This shift can help overcome some of the problems affecting the Central Rift Valley, namely: (1) the overexploitation of water resources; (2) poor water quality; and (3) the high dependency of the population on water resources to sustain their livelihoods.
This article assesses the relation between water management, environmental degradation and poverty through a stakeholder analysis focused on the status and management of water resources. It draws from the situation observed in the Ethiopian Central Rift Valley, an endorheic basin south of Addis Ababa where human activities have resulted in the degradation of most freshwater ecosystems and where the vast majority of the population lives in poverty. It proposes a shift in water governance that focuses on improving economic and social welfare and enhancing environmental sustainability. This shift can help overcome some of the problems affecting the Central Rift Valley, namely: (1) the overexploitation of water resources; (2) poor water quality; and (3) the high dependency of the population on water resources to sustain their livelihoods
Determination of reliable solute transport parameters is an essential aspect for the characterization of the mechanisms and processes involved in solute transport (e.g., pesticides, fertilizers, contaminants) through the unsaturated zone. A rapid inexpensive method to estimate the dispersivity parameter at the field scale is presented herein. It is based on the quantification by the X-ray fluorescence solid-state technique of total bromine in soil, along with an inverse numerical modeling approach. The results show that this methodology is a good alternative to the classic Br-determination in soil water by ion chromatography. A good agreement between the observed and simulated total soil Br is reported. The results highlight the potential applicability of both combined techniques to infer readily solute transport parameters under field conditions.
One of the most important issues for water resource management is developing strategies for groundwater modelling that are adaptable to data scarcity. These strategies are particularly important in arid and semi-arid areas where access to data is poor and data collection is difficult, such as the Lake Chad Basin in Africa. In the present study, we establish a numerical groundwater flow model and evaluate the effects of dry and wet periods on groundwater recharge in the Chari–Logone area (96¿000¿km2) of the Lake Chad Basin. Boundary conditions, flow direction, sources, and sinks for the Chari–Logone local model were obtained by revising and remodelling the Lake Chad Basin regional hydrogeological model (508¿400¿km2) developed by the BRGM (Bureau de Recherches Géologiques et Minières) in the 1990s. The simulated aquifer water level showed good agreement with observed levels. Aquifer recharge is primarily determined by river–aquifer interactions and mostly occurs in the southern section of the study area. In wet years, groundwater recharge also occurs in the N'Djamena area. The approach we adopted provided relevant results and was useful as an initial step in more detailed modelling of the area. It also proved to be a useful method for groundwater modelling in large semi-arid and arid regions where available data are scarce.
Poch, R.; Jiménez, J.; Wallis, K.J; Ramírez de Cartagena, F.; Candela, L. Agricultural water management Vol. 134, p. 1-13 DOI: 10.1016/j.agwat.2013.11.017 Data de publicació: 2014-03 Article en revista
Agriculture constitutes a major source of non-point pollution (e.g., nitrates) where overall water resources are affected, in particular, aquifers. Intensive agricultural practices take place in regions with appropriate weather conditions that are usually deficient in water resources. The preservation of water resources in these types of regions depends on the evaluation of the efficiency of agricultural practices for specific crops and conditions. Although water scarcity is a characteristic feature in the Western Mediterranean, it is one of the most appropriate regions in the world for intensive agriculture development for climatic reasons. In the current work, percolation and N leaching from different crops (corn, potato, and rotation of lettuce and melon) under different irrigation methods (surface, sprinkler and drip) were evaluated through experimental plots. Water (irrigation + precipitation) and fertilizer inputs were accurately controlled. Soil water content and nitrate concentration were monitored from time domain reflectometry measurements, and cup lysimeters and destructive sampling, respectively. Percolation and nitrate leaching was simulated from different numerical codes (STICS and GLEAMS, tipping bucket method; HYDRUS-1D, Richards’ equation), which were chosen based on the available information and the specific purposes of each experiment. For the studied periods, the obtained results showed high percolation values: 34, 58 and 37% of total applied water for corn, potato, and rotation of lettuce and melon, respectively. Also, high N leaching values across all experiences were observed, even higher than the applied doses in some periods as consequence of remobilizing mineralized N, despite following the recommended agricultural management practices. Percolation and N leaching were mostly controlled by the precipitation regime, namely, unevenly distributed intensive rainfall events, mainly in autumn and spring, which have a great impact in irrigated agriculture due to the permanent high soil water content. In detail, irrigation water applied for frost prevention on potato crops and plastic cover for melon crops, played a very important role for both percolation and N leaching. Whilst for the corn crop, N leaching mainly took place in the fallow period (autumn and winter), where the rain leached N present in soil from previous crops.
Gaaloul, N.; Candela, L.; Chebil, A.; Soussi, A.; Tamoh, K. Desalination and water treatment Vol. 52, num. 10-12, p. 1997-2008 DOI: 10.1080/19443994.2013.821026 Data de publicació: 2014 Article en revista
During the last few decades, the Grombalia shallow, an unconfined aquifer, had been under stress by groundwater pumping due to the increasing population and development of agricultural activity. Recently, the aquifer has displayed an important decline in the water level of boreholes and wells, and considerable deterioration of groundwater quality due to saltwater intrusion. A groundwater numerical model for the Grombalia aquifer has been developed based on the Visual Modflow 3.1 code to simulate the groundwater changes under steady state regime and transient conditions. The results of the model show reasonable agreement between observed and estimated groundwater levels in the observation wells. Sebkaht Soliman wetland aquifer connection has been identified. This paper presents the effect of different groundwater management scenarios and pumping discharge on groundwater resources in the Grombalia aquifer (Cap-Bon peninsula, Tunisia).
Corada-Fernández, C.; Lara-Martín, P.; Jimenez, J.; Candela, L.; González, E. International Conference on Environmental Science and Technology p. 436 Data de presentació: 2013-09-06 Presentació treball a congrés
Corada-Fernández, C.; Lara-Martín, P.; Candela, L.; González, E. Science of the total environment Vol. 461-462, p. 568-575 DOI: 10.1016/j.scitotenv.2013.04.100 Data de publicació: 2013-09 Article en revista
This manuscript deals with the presence and degradation of the most commonly-used surfactants, including anionic (linear alkylbenzene sulfonates, LAS, and alkyl ethoxysulfates, AES) and non-ionic (alcohol polyethoxylates, AEOs, and nonylphenol polyethoxylates, NPEOs) compounds, in sediments and pore water from several aquatic environments (Southwest, Spain). Different vertical distributions were observed according to the respective sources, uses, production volumes and physicochemical properties of each surfactant. Levels of nonionics (up to 10 mg kg- 1) were twice as high as anionics in industrial areas and harbors, whereas the opposite was found near urban wastewater discharge outlets. Sulfophenyl carboxylic acids (SPCs), LAS degradation products, were identified at anoxic depths at some sampling stations. Their presence was related to in situ anaerobic degradation of LAS in marine sediments, whereas the occurrence of these metabolites in freshwater sediments was attributed to the existence of wastewater sources nearby. No significant changes in the average length of AEO and NPEO ethoxylated chains were observed along the sediment cores, suggesting that their biodegradation was very limited in the sampling area. This may be directly related to their lower bioavailability, as their calculated sediment–pore water distribution coefficients (log Ksw), which showed that non-ionic surfactants examined in this study had greater sorption affinity than the anionic surfactants (e.g., 2.3 ± 0.3 for NPEOs).
Adsorption/desorption processes (sorption isotherms) of Naproxen in a sandy aquifer matrix sediment were investigated using batch tests to compare Naproxen sorption behavior at 15°C and 25°C. Both temperatures are representative of the aquifer media and environmental conditions. Adsorption was well described by linear isotherms with low sorption affinity to aquifer material (Kd of 0.4 µg kg-1) at both temperatures (15°C and 25°C). Desorption isotherm coefficients at 15°C and 25°C were 5.0 and 4.9, respectively. Naproxen hysteresis indices were between 9.98 and 10.8, indicating that a Naproxen fraction may be irreversibly fixed in the aquifer media, being higher at 25°C (10.88) compared to 15°C, showing a decreasing trend with increasing compound concentration at 15°C. The low sorption of Naproxen leads to potential leaching to groundwater if present in irrigation water, and its prevalence in an aquifer media when directly injected in wells for groundwater recharge.
Valdés-Abellán, J.; Candela, L.; Jiménez- Martínez, J.; Saval, J. Desalination and water treatment Vol. 51, num. 10-12, p. 2431-2444 DOI: 10.1080/19443994.2012.747506 Data de publicació: 2013 Article en revista
Environmental tracers, such as tritium, have generally been used to estimate aquifer recharge under natural conditions. A tritium tracer test is presented for estimating recharge under semi-arid and irrigated conditions. The test was performed along 429¿days (June 2007–August 2008) on an experimental plot located in SE Spain with drip irrigation and annual row crops (rotation of lettuce and melon), in which common agricultural practices were followed in open air. Tritiated water was sprinkled (simulated rainfall) over the plot, soil cores were taken at different depths and a liquid scintillation analyzer was used to measure tritium concentration in soil water samples. Tritium transport, as liquid or vapor phase, was simulated with the one-dimensional numerical code SOLVEG. Simulations show that the crop water use was below potential levels, despite regular irrigation. Continuous high water content in soil promoted a great impact of rainfall events on the aquifer recharge. The results obtained from tritium tracer test have been compared with other independent recharge assessment, soil water balance method, to evaluate the reliability of the first one. Total recharge from tracer test was 476¿mm for the October 2007–September 2008 period versus 561¿mm from soil water balance method for the same period, which represents 37.1% and 43.7% of the applied water (1284¿mm, irrigation¿+¿precipitation), respectively.
Intensive farming often leads environmental consequences. This is the case of the study area of this thesis: the Empordà, a region with a variety of intensive crops (fruits, cereals, forage,...) and manifest problems of groundwater pollution by nitrates whose origin points also to agricultural practices in the area.
The work has focusen on monoculture production of corn for grain with furrow irrigation and mineral nitrogen fertilization. Within this framework, objectives has been defined as: (1) to evaluate the influence that irrigation and nitrogen fertilization have on production and environmental impacts (groundwater pollution by nitrates), and (2) to evaluate an implement simulation codes to deepen in knowledge of irrigation and crop management in the area.
It has been defined an experimental test of two years on the same plot where five modules -with eight furrows each- of surface irrigation has been set for evaluating performance irrigation. On these modules has been sown corn and defined five different treatments -with three replicates each- resulting from the interaction of three doses of mineral nitrogen fertilizer (0, 210, and 500 kg N/ha) and two types of fertilizer: conventional (with two applications) an low release (with one application). The corn crop management was carried out according to standard practices in the study area.
The experimental plot has been intensively monitored and sampled for monitoring and for quantifying all the variables that have influenced the behavior of irrigation and crop response to the treatments done. This information has also been used for to calibrate and/or to validate the RAIEOPT, EVASUP2, SIMRAIE, SIRMOD, HYDRUS, and STICS codes.
The conclusions drawn from the results obtained on the irrigation system are: (1) first irrigation behaves very differently from other irrigations of the campaign, (2) the environment conditions where irrigation is developed are variable (furrow cross section, infiltration, soil compactation, and surface roughness) and influence on the behavior of irrigation, (3) the total dose of applied water did not exceed in any case 75% of the theoretical needs of the crop, (4) the simulation codes that best reflect observed irrigation behavior are RAIEOPT for calculating the average infiltration function and SIMRAIE for estimating doses of water infiltrated along the furrow, and (5) in the conditions experienced, the dose profiles of the infiltrated water along the furrows are practically flat.
In terms of crop response to experimental scenarios tested is concluded that: (1) treatment with no application of nitrogen fertilizer has a grain yield of about 40% lower than the other treatments, (2) there are no differences in crop yield rates on treatments with some application of mineral fertilizer nitrogen, (3) the nitrogen leaching losses are associated with periods of drainage and are proportional to soil nitrogen content at the beginning of these periods, and (4) there has been no drainage during the two irrigation periods tested.
Finally, on the simulation of soil-plant-atmosphere with STICS code is concluded that: (1) STICS is a useful tool for simulating the agricultural system in scenarios with and without crops, and (2) STICS tends to overestimate the risk of nitrate leaching observed in plot.
L’agricultura intensiva normalment porta associades conseqüències sobre el medi ambient. Aquest és el cas de l’àrea d’estudi de la present tesi doctoral: l’Empordà, una regió amb gran varietat de cultius intensius (fruiters, cereals, farratges,...) i amb problemes manifestos de contaminació d’aigües subterrànies per nitrats l’origen dels quals apunta, també, a les pràctiques agrícoles de la zona.El treball realitzat s’ha centrat en el monocultiu de blat de moro per a producció de gra amb reg per superfície en solcs i amb fertilització nitrogenada mineral. En aquest marc, s’han definit com a objectius (1) avaluar la influència que el reg i la fertilització nitrogenada tenen sobre la producció i l’impacte ambiental (contaminació subterrània per nitrats) i (2) avaluar i aplicar codis de simulació que permetin aprofundir en el coneixement del sistema de reg i el maneig del cultiu a la zona.S’ha plantejat un assaig experimental de dos anys de durada sobre la mateixa parcel•la experimental. En ella s’han configurat cinc mòduls de reg de 8 solcs cadascun per a l’avaluació del comportament del reg. Sobre aquests mòduls s’ha sembrat blat de moro i s’han definit cinc tractaments diferents (amb tres repeticions cadascun) fruit de la interacció de tres dosis de fertilitzant mineral nitrogenat (0, 210 i 500 kg N/ha) i dos tipus de fertilitzant: convencional (amb aplicacions de fons i de cobertora) i d’alliberació gradual (amb una aplicació de fons). El maneig del cultiu s’ha realitzat segons les pràctiques habituals de la regió.La parcel•la experimental s’ha monitoritzat i s’han pres mostres intensivament per a fer un seguiment i quantificar totes les variables que han influït en el comportament del reg i en la resposta agronòmica del cultiu als tractaments realitzats. Amb aquesta informació s’han calibrat i/o validat els codis de simulació RAIEOPT, EVASUP2, SIMRAIE, SIRMOD, LIXIM, HYDRUS i STICS.De l’anàlisi dels resultats obtinguts, sobre el sistema de reg per superfície es conclou que: (1) que el primer reg es comporta de forma molt diferent a la resta de regs de la campanya; (2) que les condicions del medi on es desenvolupa el reg són variables (secció transversal del solc, infiltració, compactació i rugositat del sòl) i influeixen en el comportament del reg; (3) que les dosis totals d’aigua aplicades no han superat en cap cas el 75% de les necessitats teòriques del cultiu; (4) que els codis de simulació que millor reflecteixen el comportament del reg observat són el RAIEOPT pel càlcul de la funció mitjana d’infiltració en solcs i el SIMRAIE per preveure les dosis d’aigua infiltrades al llarg del solc de reg; i (5) que, en les condicions experimentades, els perfils de les dosis d’aigua infiltrades al llarg dels solcs són pràcticament horitzontals.En quant a la resposta del cultiu als escenaris experimentals realitzats es conclou que: (1) el tractament sense aportació de fertilitzant nitrogenat té un rendiment en producció de gra de prop del 40% menor que la resta de tractaments; (2) no s’observen diferències en els índexs de rendiment del cultiu entre els tractaments amb alguna aportació de fertilitzant mineral nitrogenat; (3) les pèrdues de nitrogen per lixiviació van associades a períodes dedrenatge i són proporcionals al nitrogen present en el sòl a l’inici d’aquests períodes; i (4) no s’ha produït drenatge durant els períodes de reg assajats.Finalment, sobre la simulació del sistema sòl-planta-atmosfera amb el codi STICS es conclou que: (1) STICS és una eina útil de simulació del sistema agrícola en escenaris amb i sense cultiu; i (2) STICS tendeix a sobreestimar els risc de lixiviació de nitrats observat en parcel•la.
Jiménez-Martínez, J.; Tamoh, K.; Candela, L.; Elorza, F.J.; Hunkeler, D. Mathematical geosciences Vol. 44, num. 2, p. 187-208 DOI: 10.1007/s11004-012-9383-8 Data de publicació: 2012-02 Article en revista
Tritium is a short-lived radioactive isotope (T 1/2=12.33 yr) produced naturally in the atmosphere by cosmic radiation but also released into the atmosphere and hydrosphere by nuclear activities (nuclear power stations, radioactive waste disposal). Tritium of natural or anthropogenic origin may end up in soils through tritiated rain, and may eventually appear in groundwater. Tritium in groundwater can be re-emitted to the atmosphere through the vadose zone. The tritium concentration in soil varies sharply close to the ground surface and is very sensitive to many interrelated factors like rainfall amount, evapotranspiration rate, rooting depth and water table position, rendering the modeling a rather complex task. Among many existing codes, SOLVEG is a one-dimensional numerical model to simulate multiphase transport through the unsaturated zone. Processes include tritium diffusion in both, gas and liquid phase, advection and dispersion for tritium in liquid phase, radioactive decay and equilibrium partitioning between liquid and gas phase. For its application with bare or vegetated (perennial vegetation or crops) soil surfaces and shallow or deep groundwater levels (contaminated or non-contaminated aquifer) the model has been adapted in order to include ground cover, root growth and root water uptake. The current work describes the approach and results of the modeling of a tracer test with tritiated water (7.3×108 Bq m−3) in a cultivated soil with an underlying 14 m deep unsaturated zone (non-contaminated). According to the simulation results, the soil’s natural attenuation process is governed by evapotranspiration and tritium re-emission. The latter process is due to a tritium concentration gradient between soil air and an atmospheric boundary layer at the soil surface. Re-emission generally occurs during night time, since at day time it is coupled with the evaporation process. Evapotranspiration and re-emission removed considerable quantities of tritium and limited penetration of surface-applied tritiated water in the vadose zone to no more than ∼1–2 m. After a period of 15 months tritium background concentration in soil was attained.
Corada-Fernández, C.; Vanclooster, M.; Candela, L.; Jiménez-Martínez, J.; Smith, J.E.; González-Mazo, E. Jornadas de Investigación de la Zona no Saturada del Suelo p. 211-216 Data de presentació: 2011-10-19 Presentació treball a congrés
En este trabajo se analiza el comportamiento
de un etoxímero de tensioactivo sintético no iónico (alcoholes polietoxilados, AEOs) en condiciones no saturadas a partir de un ensayo de laboratorio mediante una célula de flujo. Se presentan los resultados de la simulación correspondientes a la aplicación del código HYDRUS y una primera aproximación del transporte del etoxímero seleccionado (C16AEO6EO). De acuerdo a los resultados
de la modelación, estos reproducen satisfactoriamente los datos experimentales, mostrando para el C16AEO6EO altos índices de degradación y adsorción en el suelo.
In this work the behavior of an ethoxymer of
non-ionic synthetic surfactant (alcohol polyethoxylates, AEOs) is studied under unsaturated conditions from a laboratory test performed in a flow cell. A first approach to the transport of the selected ethoxymer (C16AEO6EO) using HYDRUS code is presented. The results from modeling reproduce the experimental data successfully,
showing a high degradation rate as well as soil adsorption of C16AEO6EO.infiltration and the delay in runoff generation.