Nicolas Greggio

Seasonal dynamic of a shallow freshwater lens due to irrigation in the coastal plain of Ravenna, Italy

Irrigation in low-lying coastal plains may enhance the formation of fresh groundwater lenses, which counteract salinization of groundwater and soil. This study presents seasonal dynamics of such a freshwater lens and discusses its influence on the salinity distribution of the unconfined aquifer in the coastal plain of Ravenna, Italy, combining field observations with numerical modeling (SEAWAT). The lens originates from an irrigation ditch used as a water reservoir for spray irrigation. The geometry of the freshwater lens shows seasonal differences because of freshwater infiltration during the irrigation season and upconing of deeper saltwater for the remainder of the year. The extent of the freshwater lens is controlled by the presence of nearby drainage ditches. Irrigation also results in a temperature anomaly in the aquifer because of the infiltration of warm water during the irrigation season. The surficial zone in the vicinity of the irrigation ditch is increased considerably in thickness. Finally, different irrigation alternatives and the influence of sea-level rise are simulated. This shows that it is necessary to integrate irrigation planning into the water management strategy of the coastal zone to have maximum benefits for freshening of the aquifer and to make optimal use of the existing infrastructure.RésuméL’irrigation dans les basses plaines côtières est susceptible de favoriser la formation de lentilles d’eaudouce, qui s’opposent à la salinisation de l’eau souterraine et des sols. Cette étude présente ladynamique saisonnière d’une telle lentille d’eau douce et discute de son influence sur la distribution desalinité dans l’aquifère à nappe libre de la plaine côtière de Ravenne en Italie, combinant desobservations de terrain avec une modélisation numérique (SEAWAT). La lentille provient d’un fosséd’irrigation utilisé comme réservoir d’eau pour l’irrigation par aspersion. La géométrie de la lentilled’eau douce montre des différences saisonnières à cause de l’infiltration d’eau douce durant la saisond’irrigation et des remontées d’eau salées pendant le reste de l’année. L’extension de la lentille d’eaudouce est contrôlée par la présence des fossés voisins. L’irrigation a aussi comme conséquence uneanomalie thermique dans l’aquifère du fait de l’infiltration d’eau à température ambiante pendant lasaison d’irrigation. L’épaisseur de la zone superficielle augmente considérablement au voisinage dufosse d’irrigation Enfin, diverses alternatives d’irrigation et l’influence de l’augmentation du niveau dela mer sont simulées. Elles montrent que l’intégration d’un schéma d’irrigation dans la stratégie degestion de l’eau en zone côtière est nécessaire pour obtenir les avantages maximum pour adoucir lanappe et faire une utilisation optimale de l’infrastructure existante.ResumenLa irrigación en planicies costeras bajas puede favorecer la formación de lentes de agua subterráneadulce, las cuales contrarrestan la salinización del agua subterránea y del suelo. Este estudio presenta ladinámica estacional de una de tales lentes de agua dulce y discute su influencia en la distribución de lasalinidad del acuífero no confinado en la planicie costera de Ravenna, Italia, combinandoobservaciones de campo con modelado numerico (SEAWAT). La lente se origina a partir de unaacequia usada como un reservorio de agua para la irrigación por aspersión. La geometría de la lente deagua dulce muestra diferencias estacionales debido a que la infiltración de agua dulce durante de laestación de irrigación y el desplazamiento vertical de agua salina más profunda durante el resto delaño. La extensión de la lente de agua dulce está controlada por la presencia de acequias de drenajecercanas. La irrigación también produce una anomalía en la temperatura del acuífero debido a lainfiltración de agua cálida durante la estación de irrigación. La zona superficial en la vecindad de laacequia de irrigación incrementa considerablemente su espesor. Finalmente, se simulan las diferentesalternativas de irrigación y la influencia del ascenso del nivel del mar. Esto muestra que la integraciónde la planificación de la irrigación dentro de la estrategia de manejo del agua de la zona costera esnecesaria para obtener los máximos beneficios y para proveer de agua dulce al acuífero y hacer un usoóptimo de la infraestructura existente.摘要低洼沿海平原灌溉可增加地下淡水透镜体的形成, 从而抵消地下水和土壤的盐度。结合野外观测和数值模拟, 本研究展示了这样的淡水透镜体的季节性动态变化, 论述了淡水透镜体对意大利Ravenna (拉文那) 沿海平原非承压含水层盐度分布的影响。透镜体源自作为喷灌储水池的灌溉渠沟。由于灌溉期间的淡水渗透及其他时间内出现的深部咸水倒锥, 透镜体的几何结构显示出季节性差异。淡水透镜体的范围受附近排水沟的控制。由于灌溉季节温水的渗透, 灌溉也导致含水层温度异常。灌溉沟渠附近的表层带厚度增加非常大。最后, 模拟了不同的灌溉替代选择及海平面上升的影响。表明, 有必要制定综合的沿海地区水管理战略灌溉规划, 以获取含水层淡化的最 大效益及优化利用现有的基础设施。ResumoA rega em planícies costeiras de zonas baixas pode induzir a formação de lentes de água doce queimpedem a salinização da água subterrânea e do solo. Este estudo apresenta a dinâmica sazonal deuma destas lentes de água doce e analisa a sua influência na distribuição da salinidade do aquíferofreático na planície costeira de Ravenna, Itália, combinando campos de observação com modelaçãomatemática (SEAWAT). A lente forma-se a partir de um açude que é usado como reservatório de águapara rega por aspersão. A geometria da lente de água doce mostra diferenças sazonais devido àinfiltração de água doce durante o período de rega e ascensão de água salgada mais profunda durante oresto do ano. A dimensão da lente de água doce é controlada pela presença de valas de drenagempróximas. A rega também induz uma anomalia de temperatura no aquífero devido à infiltração de águaquente durante o período de rega. A zona superficial nas proximidades do açude de rega aumentousignificativamente de espessura. Finalmente, foram simuladas alternativas distintas de rega e ainfluência do aumento do nível do mar. Isto demonstra que a integração do planeamento da rega noâmbito da estratégia de gestão de água da zona costeira é necessária para obter o máximo rendimentoda introdução de água doce no aquífero e para fazer o melhor uso da infraestrutura existente.

Irrigation Management in Coastal Zones to Prevent Soil and Groundwater Salinization

Soil salinization is one of the most widespread soil degradation processes on earth and, worldwide, one billion hectares are affected, mainly in the arid–semiarid regions of Asia, Australia and South America [1]. In Europe, soil salinity has effects on one million hectares mainly in the Mediterranean countries [1]. There are two types of salinization: primary salinization caused by natural events such as sea spray or rock weathering or seepage [2] and secondary salinization that is caused by human activities such as irrigation with salty water, groundwater overexploitation and excessive drainage [1].

Coastal aquifer response to extreme storm events in Emilia‐Romagna, Italy

With global warming and sea level rise, many coastal systems will experience increased levels of inundation and storm flooding, especially along sandy lowland coastal areas, such as the Northern Adriatic coast (Italy). Understanding how extreme events may directly affect groundwater hydrology in shallow unconfined coastal aquifers is important to assess coastal vulnerability and quantifying freshwater resources. This study investigates shallow coastal aquifer response to storm events. The transitory and permanent effects of storm waves is evaluated through the real time monitoring of groundwater and soil parameters, in order to characterize both the saturated and unsaturated portions of the coastal aquifer of Ravenna and Ferrara (southern Po Delta, Italy). Results highlight a general increase in hydraulic head and soil moisture, along with a decrease in groundwater salinity and pore water salinity due to rainfall infiltration during the 2 days storm event. The only exceptions are represented by the observation wells in proximity to the coastline (within 100 m), which recorded a temporary increase in soil and water salinity caused by the exceptional high waves, which persist on top of the dune crest during the storm event. This generates a saline plume that infiltrates through the vadose zone down to the saturated portion of the aquifer causing a temporary disappearance of the freshwater lens generally present, although limited in size, below the coastal dunes. Despite the high hydraulic conductivity, the aquifer system does not quickly recover the pre-storm equilibrium and the storm effects are evident in groundwater and soil parameters after 10 days past the storm overwash recess.

Forest fire effects on groundwater in a coastal aquifer (Ravenna, Italy)

BiGeA—Department of Biological, Geological and Environmental Sciences, University of Bologna, Ravenna, Italy CIRI EA—Interdepartmental Centre for Industrial Research on Energy and Environment, University of Bologna, Ravenna, Italy Carabinieri for Biodiversity, Punta Marina, Ravenna, Italy Correspondence Nicolas Greggio, CIRI EA—Interdepartmental Centre for Industrial Research on Energy and Environment, University of Bologna, 48123 Ravenna, Italy. Email: nicolas.greggio2@unibo.it Funding information Flaminia Foundation

Effects of saltwater intrusion on pinewood vegetation using satellite ASTER data: the case study of Ravenna (Italy)

The San Vitale pinewood (Ravenna, Italy) is part of the remaining wooded areas within the southeastern Po Valley. Several studies demonstrated a widespread saltwater intrusion in the phreatic aquifer caused by natural and human factors in this area as the whole complex coastal system. Groundwater salinization affects soils and vegetation, which takes up water from the shallow aquifer. Changes in groundwater salinity induce variations of the leaf properties and vegetation cover, recognizable by satellite sensors as a response to different spectral bands. A procedure to identify stressed areas from satellite remote sensing data, reducing the expensive and time-consuming ground monitoring campaign, was developed. Multispectral Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data, acquired between May 2005 and August 2005, were used to calculate Normalized Difference Vegetation Index (NDVI). Within the same vegetation type (thermophilic deciduous forest), the areas with the higher vegetation index were taken as reference to identify the most stressed areas using a statistical approach. To confirm the findings, a comparison was conducted using contemporary groundwater salinity data. The results were coherent in the areas with highest and lowest average NDVI values. Instead, to better understand the behavior of the intermediate areas, other parameters influencing vegetation (meteorological data, water table depth, and tree density) were added for the interpretation of the results.