Catalin Stefan

Web-based global inventory of managed aquifer recharge applications

Managed aquifer recharge (MAR) is being successfully implemented worldwide for various purposes: to increase groundwater storage, improve water quality, restore groundwater levels, prevent salt water intrusion, manage water distribution systems, and enhance ecological benefits. To better understand the role of MAR in sustainable water management and adaptation to climate and land use change, about 1200 case studies from 62 countries were collected and analyzed with respect to historical development, site characterization, operational scheme, objectives and methods used, as well as quantitative and qualitative characterization of in- and outflow of water. The data harvested was used for the compilation of a global inventory of MAR schemes, whose main goal is to provide access to existing MAR projects and techniques and demonstrate their benefits. To increase the availability and facilitate continuous update of the MAR inventory, an MAR web-based portal was developed and integrated into IGRAC’s Global Groundwater Information System. The MAR portal contains a “data layer catalog” containing the data arranged in a systematic way, a “map viewer” to visualize the selected data on a geographic location, and a “features panel” providing tabular output of the selected data. By facilitating access and promoting international sharing of information and knowledge on MAR, the web-based MAR portal aims to increase awareness of MAR as a viable solution for sustainable groundwater resources development and management, and to provide a new tool for better planning of MAR at regional and global scale.

Inventory of managed aquifer recharge schemes in Latin America and the Caribbean

Managed aquifer recharge (MAR) is being used worldwide as a tool to overcome distinct water management challenges. An analysis of MAR case studies from different countries in Latin America and the Caribbean (LAC) was carried out as part of a larger study focused on the compilation of a global inventory of MAR schemes which aims at providing guidance for the planning and implementation of new MAR projects. The MAR case studies were collected from freely available scientific publications. These were classified according to the specific MAR type developed, main objective and the source of the influent water. Most reported cases (>60%) were found in Brazil, followed by Mexico and Chile. The main MAR type reported in LAC is in-channel modification, which represents more than half of the reported MAR schemes, and the main influent water used is river water and storm water (together accounting for >90% of cases). Approximately two-thirds of the MAR cases in LAC were developed to maximize natural storage. Publication of freely available scientific reports on MAR in LAC is scarce; however, this is not due to lack of MAR projects, but rather suggests insufficient motivation in sharing experiences with the international scientific community. Nevertheless, MAR has been successfully implemented in at least ten LAC countries. For four of these, estimates of annual recharge volume are available—Mexico (156 Mm3), Cuba (115 Mm3), Peru (36 Mm3) and Costa Rica (4 Mm3)—and a further 30 Mm3 are crudely but conservatively calculated for the remaining LAC countries (mostly in Brazil) bringing the total to approximately 340 Mm3. The application of MAR is expected to grow further as a sustainable and reliable tool to address challenges related to climate, population and economic changes.

Utilizing unsaturated soil zone models for assessing managed aquifer recharge

Managed aquifer recharge (MAR) is increasingly used to balance out the divergence between natural groundwater recharge and overexploitation of groundwater resources. As testing and design of recharge facilities can be cost and time-intensive, modeling tools hold great potential to design field investigations as well as to augment and extrapolate from their results. Focusing on unsaturated soil zone models, this study first reviews 16 previous modeling studies showing their range of model types and applications. The review is accompanied by an example of the use of HYDRUS 2D/3D, an unsaturated zone model, to design a novel small-scale infiltration basin. The basin is going to be established as part of a field and laboratory research facility for MAR in Pirna, Germany. Modeling results assisted in determining the dimensions of the infiltration unit as well as the placement of measurement devices and experimental scenario planning. Finally, the strengths and constraints of this modeling approach for MAR assessment are discussed.

Adsorption and Abiotic Degradation of Methyl tert-Butyl Ether (MTBE)

This chapter explores the role of abiotic reactions such as acid catalysis (hydrolysis) as well as the adsorption of methyl tert-butyl ether (MTBE) and other fuel oxygenates in environmental issues as the remediation of these substances is notoriously difficult. First of all, these methods are briefly classified with other abiotic technologies. The suitability of hydrolysis and adsorption for the remediation of water contaminated by fuel oxygenates is then discussed in detail, with information being provided about the principle of the reactions, potential catalysts and sorbents, limitations of the reactions, and practical implications. To conclude, the possible application of hydrolysis and adsorption in combination with other remediation techniques is also examined.

Simulation of the impact of managed aquifer recharge on the groundwater system in Hanoi, Vietnam

A transient numerical groundwater flow model using MODFLOW-NWT was set up and calibrated for Hanoi city, Vietnam, to understand the local groundwater flow system and to suggest solutions for sustainable water resource management. Urban development in Hanoi has caused a severe decline of groundwater levels. The present study evaluates the actual situation and investigates the suitability of managed aquifer recharge (MAR) to stop further depletion of groundwater resources. The results suggest that groundwater is being overexploited, as vast cones of depression exist in parts of the study area. Suitable locations to implement two MAR techniques—riverbank filtration and injection wells—were identified using multi-criteria decision analysis based on geographic information system (GIS). Three predictive scenarios were simulated. The relocation of pumping wells towards the Red River to induce riverbank filtration (first scenario) demonstrates that groundwater levels can be increased, especially in the depression cones. Groundwater levels can also be improved locally by the infiltration of surplus water into the upper aquifer (Holocene) via injection wells during the rainy season (second scenario), but this is not effective to raise the water table in the depression cones. Compared to the first scenario, the combination of riverbank filtration and injection wells (third scenario) shows a slightly raised overall water table. Groundwater flow modeling suggests that local overexploitation can be stopped by a smart relocation of wells from the main depression cones and the expansion of riverbank filtration. This could also avoid further land subsidence while the city’s water demand is met.RésuméUn modèle numérique d’écoulement souterrain transitoire à l’aide de MODFLOW-NWT a été élaboré et calibré pour la ville de Hanoï au Vietnam, pour comprendre le système d’écoulement local des eaux souterraines et pour suggérer des solutions pour la gestion durable des ressources en eau. Le développement urbain à Hanoï a entrainé une baisse importante;des niveaux d’eaux souterraines. La présente étude évalue la situation actuelle et étudie la convenance de la recharge raisonnée ou artificielle d’un aquifère (MAR) pour stopper l’épuisement des ressources en eaux souterraines. Les résultats suggèrent que les eaux souterraines sont surexploitées, car de vastes cônes de dépression existent dans certaines parties du secteur d’étude. Des endroits appropriés à la mise en place de deux méthodes de recharge artificielle—la filtration à travers les berges et les puits d’injection—ont été identifiées en utilisant une analyze de décision multi-critères basée sur un système d’information géographique (SIG). Trois scénarios prédictifs ont été simulés. La relocalisation des puits de pompage vers le Fleuve Rouge pour induire de la filtration à travers les berges (premier scénario) démontre que des niveaux d’eaux souterraines peuvent être relevés, particulièrement dans les cônes de dépression. Les niveaux d’eaux souterraines peuvent également être améliorés localement par l’infiltration de l’eau en surplus dans la couche aquifère supérieure (Holocène) par l’intermédiaire de puits d’injection pendant la saison des pluies (deuxième scénario), mais ce n’est. pas efficace pour rehausserle niveau de la nappe dans les cônes de dépression. Comparé au premier scénario, la combinaison de la filtration à travers les berges et des puits d’injection (troisième scénario) montre seulement un léger relèvement global de la nappe. La modélisation des écoulements souterrains suggère que la surexploitation locale pourrait être arrêtée par une relocalisation pertinente des puits situés dans les cônes de dépression principaux et par l’expansion de la technique de filtration à travers les berges. Ceci pourrait également éviter davantage d’affaissement de terrain tout en satisfaisant toujours la demande en eau de la ville.ResumenSe configuró y calibró un modelo de flujo subterráneo de agua subterránea con MODFLOW-NWT para la ciudad de Hanoi, Vietnam, para comprender el sistema local de flujo de aguas subterráneas y sugerir soluciones para la gestión sostenible de los recursos hídricos. El desarrollo urbano en Hanoi ha causado una disminución severa de los niveles de agua subterránea. El presente estudio evalúa la situación actual e investiga la idoneidad de la recarga de acuíferos gestionados (MAR) para detener el agotamiento de los recursos de agua subterránea. Los resultados sugieren que el agua subterránea se está sobreexplotando, ya que existen grandes conos de depresión en partes del área de estudio. Se identificaron ubicaciones adecuadas para implementar dos técnicas de MAR (pozos de filtración e inyección de ribera) utilizando un análisis de decisión multicriterio basado en el sistema de información geográfica (SIG). Se simularon tres escenarios predictivos. La reubicación de los pozos de bombeo hacia el Río Rojo para inducir la filtración de la ribera (primer escenario) demuestra que los niveles de agua subterránea pueden aumentar, especialmente en los conos de depresión. Los niveles de agua subterránea también pueden mejorarse localmente mediante la infiltración de agua excedente en el acuífero superior (Holoceno) a través de pozos de inyección durante la estación lluviosa (segundo escenario), pero esto no es efectivo para elevar el nivel freático en los conos de depresión. En comparación con el primer escenario, la combinación de pozos de filtración e inyección de ribera (tercer escenario) muestra solo un nivel freático general ligeramente elevado. El modelado del flujo de agua subterránea sugiere que la sobreexplotación local puede detenerse mediante una reubicación inteligente de los pozos de los principales conos de depresión y la expansión de la filtración de la ribera. Esto también podría evitar un hundimiento adicional de la tierra mientras se satisface la demanda de agua de la ciudad.摘要采用MODFLOW-NWT建立并校正了越南河内瞬时数值地下水流模型,以便了解当地地下水流系统并为可持续的水资源管理提出解决办法。河内的城市发展导致地下水位下降。目前的研究评价了世纪情况,调查了为阻止地下水资源枯竭而采取的含水层管理补给的适用性。结果显示,地下水处于超采状态,在研究区部分地区出现很大的下降漏斗。根据地理信息系统采用多标准决策分析方法确定了实施含水层管理补给两个技术的合适地点—河岸入渗和注水井。模拟了三种预测方案。抽水井朝红河方向重新布置引起河岸入渗(第一种方案)证明,地下水位可以升高,特别是在漏斗区。雨季通过注入井将多余的水渗入上层含水层(全新世)也可以使地下水位局部抬升,但对于抬升漏斗区的地下水位无效。与第一种方案相比,河岸入渗和注入井结合一起(第三种方案)显示,地下水位只有稍微的抬升。地下水流建模显示,可通过把漏斗区的井转移到更合适的位置以及扩大河岸入渗规模可以阻止局部超采。这项措施还可以在满足城市用水需求的同时避免进一步的地面沉降。ResumoUm modelo transiente de fluxo das águas subterrâneas usando o MODFLOW-NWT foi construído e calibrado para a cidade de Hanói, no Vietnã, para entender o sistema de fluxo local e sugerir soluções para o gerenciamento sustentável dos recursos hídricos. O desenvolvimento urbano em Hanoi causou um grave declínio dos níveis das águas subterrâneas. O presente estudo avalia a situação atual e investiga a adequação do gerenciamento da recarga artificial de aquíferos (GRA) para impedir o esgotamento dos recursos hídricos subterrâneos. Os resultados sugerem que as águas subterrâneas estão sendo superexplorada, pois existem vastos cones de depressão em partes da área de estudo. Locais adequados para implementar duas técnicas de GRA—filtração em margem e poços de injeção—foram identificados usando análise de decisão multicritério baseada em sistema de informação geográfica (SIG). Três cenários preditivos foram simulados. A realocação dos poços de bombeamento em direção ao Rio Vermelho para induzir a filtração em margem (primeiro cenário) demonstra que os níveis das águas subterrâneas podem ser elevados, especialmente nos cones de depressão. Os níveis das águas subterrâneas também podem sem aumentados localmente pela infiltração de água excedente no aquífero superior (Holoceno) através de poços de injeção durante a estação chuvosa (segundo cenário), mas isso não é eficaz para elevação o lençol freático nos cones de depressão. Comparado com o primeiro cenário, a combinação de filtração de margem e poços de injeção (terceiro cenário) mostra apenas um lençol freático geral ligeiramente elevado. A modelagem de fluxo das águas subterrâneas sugere que a superexploração local pode ser interrompida por uma realocação inteligente dos poços dos principais cones de depressão e pela expansão da filtração em margem. Isso também poderia evitar a subsidência de terreno enquanto a demanda de água da cidade é atendida.

Multi-Objective Optimization of Managed Aquifer Recharge: Multi-Objective Optimization of Managed Aquifer Recharge

This study demonstrates the utilization of a multi-objective hybrid global/local optimization algorithm for solving managed aquifer recharge (MAR) design problems, in which the decision variables included spatial arrangement of water injection and abstraction wells and time-variant rates of pumping and injection. The objective of the optimization was to maximize the efficiency of the MAR scheme, which includes both quantitative and qualitative aspects. The case study used to demonstrate the capabilities of the proposed approach is based on a published report on designing a real MAR site with defined aquifer properties, chemical groundwater characteristics as well as quality and volumes of injected water. The demonstration problems include steady state and transient scenarios. The steady state scenario demonstrates optimization of spatial arrangement of multiple injection and recovery wells, whereas the transient scenario was developed with the purpose of finding optimal regimes of water injection and recovery at a single location. Both problems were defined as multi-objective problems. The scenarios were simulated by applying coupled numerical groundwater flow and solute transport models: MODFLOW-2005 and MT3D-USGS. The applied optimization method was a combination of global (the non-dominated sorting genetic algorithm [NSGA-2]) and local (the Nelder-Mead downhill simplex search algorithms). The analysis of the resulting Pareto optimal solutions led to the discovery of valuable patterns and dependencies between the decision variables, model properties, and problem objectives. Additionally, the performance of the traditional global and the hybrid optimization schemes were compared.

Web-based tool compilation of analytical equations for groundwater management applications

Abstract The INOWAS platform provides a compilation of free web-based tools for groundwater management. All tools are running on a web server and can be accessed via standard web browsers. The implemented analytical equations enable the assessment of saltwater intrusion induced by pumping or sea level rise, the calculation of travel time through unconfined aquifers and the evaluation of pumping-induced river drawdown. The groundwater mounding calculator can be used to estimate the rise of groundwater levels underneath infiltration basins. To determine the contaminant concentration downgradient of a constant source, an analytical tool solving the advection-dispersion equation can be utilized. All tools are incorporated into a decision support environment. The user is provided with detailed online support that contains the theoretical background of the tools, possible applications and examples.