Search results for "Flow"

Experiments for testing soil texture effects on flow resistance in mobile bed rills

2018

Abstract In this paper a recently theoretically deduced rill flow resistance equation, based on a power-velocity profile, was tested experimentally on plots of varying slopes and soil texture in which mobile bed rills are incised. Measurements of flow velocity, water depth, cross section area, wetted perimeter and bed slope conducted in rill reaches incised on experimental plots, having different slope values (9, 14, 22, 24 and 26%) and soil texture (clay fraction ranging from 42 to 73%), and literature data were used to calibrate the flow resistance equation. In particular, the relationship between the velocity profile parameter Γ, the channel slope, the flow Froude number and texture frac…

Flow-induced vegetation uprooting in a meandering bend : experimental investigation

2022

Abstract Vegetation uprooting is a complex process which depends on many interrelated factors. In this paper, attention is focused on the flow-induced uprooting in river bends, where the flow characteristics vary as effected by the channel's curvature and its continuous changing in the downstream direction. Results are presented by an experimental work done in a high-amplitude meandering flume with mature herbaceous vegetation on the bed. In the first part of the paper, the variation along the bend of the geometrical (length, thickness, and radical architecture) and the mechanical (resistance force) characteristics of the roots are analyzed. In the second part of the paper, the transition f…

The use of constructed wetlands for the treatment of agro-industrial wastewater – A case study in a dairy-cattle farm in Sicily (Italy)

2017

Wastewaters generated by agro-industrial operations often represent an unsustainable cost for farms due to high wastewater-treatment management costs. The wastewater produced by dairies, wineries or oil mills may vary in quantity and in quality depending on the time of the year, making the use of a conventional treatment system less efficient and more costly. Constructed wetland systems (CWs) provide low-cost technology and an efficient solution in the treatment of a number of wastewaters from agriculture. They are simple to build, have low maintenance costs and are sustainable compared to conventional treatment methods. This paper shows a case study that was carried out on a dairy-cattle f…

CO2 release to the atmosphere from thermal springs of Sperchios Basin and northern Euboea (Greece): The contribution of “hidden” degassing

2020

Abstract Greece is a region characterised by intense geodynamic activity that favours the circulation of hydrothermal fluids in the crust transporting volatiles from either the deep crust or the mantle to the surface. Elevated heat flow values are detectable at Sperchios Basin and North Euboea (central Greece), two areas defined by a system of deeply rooted extensional faults and Quaternary volcanic activity. This setting contributed to the formation of numerous hydrothermal systems, which are mostly expressed as CO2-rich thermal springs with intense bubbling. The CO2 output from six bubbling pools has been determined by flux measurements with the use of the floating chamber method. The hig…

El Lahar Tinguiririca: su significado entre los Lahares chilenos

1982

The Tinguiririca lahar is an example of many similar landforms, which cover large surfaces 60th in andine valleys and the Chilean longitudinal depression. I t is smaller than other ones in Chile, but - at the same time - better conserved, offering good conditions for genetic, kinematic and geochronologic studies, respecting volcanic mudflows. From the genetic and kinematic point of view, the longitudinal lahar profile may be in two parts: a) An upper and middle accumulative area, with concave transverse profile; b) A low accumulative area; whose transverse profile is convexe. These two profiles could be explained by means of braking process in lateral parts, related to central parts, as a f…

Flow changes and geochemical anomalies in warm and cold springs associated with the 1992-1994 seismic sequence at Pollina, Central Sicily, Italy

2007

During a three-year discontinuous geochemical monitoring of some warm springs and cold discharges located in central-northern Sicily, some hydro-geochemical changes were observed. Excluding a possible related to a moderate seismic activity were accidentally identified. The observed anomalies showed amplitudes that were modulated by the different geometries and volumes of the feeding aquifers. A poroelastic aquifer contraction, a shaking-induced dilatancy theory as well as seismogenetic-induced changes in the properties of the aquifers have been proposed as possible mechanisms for the water flow and hydro-geochemical changes. These preliminary results could be used to design a monitoring net…

2017

Abstract. The aim of this study is to present a framework that provides new ways to characterize the spatio-temporal variability of lateral exchanges for water flow and solute transport in a karst conduit network during flood events, treating both the diffusive wave equation and the advection–diffusion equation with the same mathematical approach, assuming uniform lateral flow and solute transport. A solution to the inverse problem for the advection–diffusion equations is then applied to data from two successive gauging stations to simulate flows and solute exchange dynamics after recharge. The study site is the karst conduit network of the Fourbanne aquifer in the French Jura Mountains, wh…

Growth of Arundo donax L. and Cyperus alternifolius L. in a horizontal subsurface flow constructed wetland using pre-treated urban wastewater - a cas…

2013

Constructed wetland systems for wastewater treatment represent an excellent opportunity for the recovery of water resources in those areas subject to prolonged periods of water shortage. This paper presents a study of the efficiency of a pilot horizontal subsurface flow system using pre-treated urban wastewater from a small town in the West of Sicily. The pilot system had a total surface area of 100 m2 with two units. Unit A was planted with Arundo donax L. and unit B with Cyperus alternifolius L. The HLR was 10 cm d-1. The main objectives of research were to evaluate the growth and biomass yield of two macrophytes and determine the removal efficiency of physical-chemical and microbiologica…

Environmental Variables and Planktonic Communities in Two Ponds of El Hondo Wetland (SE Spain)

2001

The annual cycle of physical and chemical variables and plankton dynamics was studied in two shallow ponds (East and West Ponds) of the El Hondo wetland, an ecosystem of international importance. Water conductivity increased up to 31-49 mS cm -1 as water level decreased due to high evaporation and minimal water inputs. Initially considered mesohaline, the waters were reclassified as polyhaline during the hot season. EP was subject to successive desiccation-flooding cycles, and flooding of the dried sediment caused the release of high concentrations of nitrogen and phosphorus compounds, which quickly depleted. The algal species composition was typical of eutrophic ecosystems, and the chlorop…

A multi-gene approach reveals a complex evolutionary history in the Cyanistes species group

2011

Quaternary climatic oscillations have been considered decisive in shaping much of the phylogeographic structure around the Mediterranean Basin. Within this paradigm, peripheral islands are usually considered as the endpoints of the colonization processes. Here, we use nuclear and mitochondrial markers to investigate the phylogeography of the blue tit complex (blue tit Cyanistes caeruleus, Canary blue tit C. teneriffae and azure tit C. cyanus), and assess the role of the Canary Islands for the geographic structuring of genetic variation. The Canary blue tit exhibits strong genetic differentiation within the Canary Islands and, in combination with other related continental species, provides a…