Active-distributed temperature sensing to continuously quantify vertical flow in boreholes

We show how a distributed borehole flowmeter can be created from armored Fiber Optic cables with the Active-Distributed Temperature Sensing (A-DTS) method. The principle is that in a flowing fluid, the difference in temperature between a heated and unheated cable is a function of the fluid velocity. We outline the physical basis of the methodology and report on the deployment of a prototype A-DTS flowmeter in a fractured rock aquifer. With this design, an increase in flow velocity from 0.01 to 0.3 m s−1 elicited a 2.5°C cooling effect. It is envisaged that with further development this method will have applications where point measurements of borehole vertical flow do not fully capture combined spatiotemporal dynamics

Characterizing groundwater flow and heat transport in fractured rock using Fiber-Optic Distributed Temperature Sensing

International audienceWe show how fully distributed space-time measurements with Fiber-Optic Distributed Temperature Sensing (FO-DTS) can be used to investigate groundwater flow and heat transport in fractured media. Heat injection experiments are combined with temperature measurements along fiber-optic cables installed in boreholes. Thermal dilution tests are shown to enable detection of cross-flowing fractures and quantification of the cross flow rate. A cross borehole thermal tracer test is then analyzed to identify fracture zones that are in hydraulic connection between boreholes and to estimate spatially distributed temperature breakthrough in each fracture zone. This provides a significant improvement compared to classical tracer tests, for which concentration data are usually integrated over the whole abstraction borehole. However, despite providing some complementary results, we find that the main contributive fracture for heat transport is different to that for a solute tracer

Plant growth drives soil nitrogen cycling and N-related microbial activity through changing root traits

Relationships between plants and nitrogen-related microbes may vary with plant growth. We investigated these dynamic relationships over three months by analyzing plant functional traits (PFT), arbuscular mycorrhizal fungal (AMF) colonization, potential N mineralization (PNM), potential nitrification (PNA) and denitrification activities (PDA) in Dactylis glomerata cultures. D. glomerata recruited AMF during early growth, and thereafter maintained a constant root colonization intensity. This may have permitted high enough plant nutrient acquisition over the three months as to offset reduced soil inorganic N. PFT changed with plant age and declining soil fertility, resulting in higher allocation to root biomass and higher root C:N ratio. Additional to root AMF presence, PR' changes may have favored denitrification over mineralization through changes in soil properties, particularly increasing the quality of the labile carbon soil fraction. Other PFT changes, such as N uptake, modified the plants' ability to compete with bacterial groups involved in N cycling. (C) 2020 Elsevier Ltd and British Mycological Society. All rights reserved.Peer reviewe

Thermal-plume fibre optic tracking (T-POT) test for flow velocity measurement in groundwater boreholes

We develop an approach for measuring in-well fluid velocities using point electrical heating combined with spatially and temporally continuous temperature monitoring using distributed temperature sensing (DTS). The method uses a point heater to warm a discrete volume of water. The rate of advection of this plume, once the heating is stopped, equates to the average flow velocity in the well. We conducted thermal-plume fibre optic tracking (T-POT) tests in a borehole in a fractured rock aquifer with the heater at the same depth and multiple pumping rates. Tracking of the thermal plume peak allowed the spatially varying velocity to be estimated up to 50 m downstream from the heating point, depending on the pumping rate. The T-POT technique can be used to estimate the velocity throughout long intervals provided that thermal dilution due to inflows, dispersion, or cooling by conduction does not render the thermal pulse unresolvable with DTS. A complete flow log may be obtained by deploying the heater at multiple depths, or with multiple point heaters

Active-Distributed Temperature Sensing to continuously quantify vertical flow in boreholes

We show how a distributed borehole flowmeter can be created from armored Fiber Optic cables with the Active-Distributed Temperature Sensing (A-DTS) method. The principle is that in a flowing fluid, the difference in temperature between a heated and unheated cable is a function of the fluid velocity. We outline the physical basis of the methodology and report on the deployment of a prototype A-DTS flowmeter in a fractured rock aquifer. With this design, an increase in flow velocity from 0.01 to 0.3 m s⁻¹ elicited a 2.5°C cooling effect. It is envisaged that with further development this method will have applications where point measurements of borehole vertical flow do not fully capture combined spatiotemporal dynamics.Keywords: Fiber optics, A-DTS, Flowmeter, Heated, Borehol

Rôles,impacts et services issus des élevages en Europe. Synthèse du rapport d’expertise scientifique collective

L’élevage, secteur majeur pour l’économie de nombreux territoires et structurant beaucoup de paysages ruraux européens, fait l’objet de controverses, depuis au moins une décennie, notamment du fait des dommages environnementaux qu’il engendre. Dans un tel contexte, il est apparu nécessaire d’étayer les débats en faisant le point sur l’état des connaissances scientifiques relatives aux rôles, impacts et services environnementaux, économiques et sociaux issus des élevages européens et leurs produits. Pour ce faire, les ministères français en charge de l’Environnement et de l’Agriculture ainsi que l’Agence de l’environnement et de la maîtrise de l’énergie (Ademe) ont sollicité l’Inra pour réaliser une expertise scientifique collective (ESCo) abordant conjointement les multiples conséquences sur les milieux et le climat, l’emploi et le travail, les marchés et certains enjeux sociaux et culturels, de la production et de la consommation humaine de produits d’origine animale (bovins, ovins, caprins, porcins et avicoles). L’analyse de ces diverses dimensions s’appuie sur les démarches d’évaluation rapportées dans la littérature scientifique internationale. Abordées, dans un premier temps, de manière analytique et globale, les connaissances ont ensuite été mobilisées par « bouquet de services » au sein de territoires contrastés. Les relations entre les différents impacts ou services permettent d’identifier des compromis et des leviers d’action envisageables pour les systèmes d’élevage. Livestock production is a sector of major economic importance that defines many European rural areas. It has become the focus of controversy over the past decade or more, particularly with regard to the environmental impacts it causes. In this context, it seemed useful to support this debate with a critical review of the state of scientific knowledge on the role, impacts, and services – environmental, economic, and social – associated with European livestock production. Accordingly, the French ministries responsible for Agriculture and the Environment, in cooperation with the French Environment and Energy Management Agency (ADEME), requested INRA to undertake a collective scientific assessment addressing the many consequences – for the environment and the climate, for employment and labor, for markets, and for a variety of social and cultural issues – related to the production and human consumption of animal products (cattle, sheep, goats, pigs, and poultry). Analysis of these diverse dimensions was based on assessment methods utilized and described in the international scientific literature. Using a broad, analytical overview as a starting point, the review proceeded by identifying the "service bundles" associated with livestock production in contrasting areas

SelkerJohnBioEcoEngineeringActive-DistributedTemperature_AuxiliaryMaterial.zip

We show how a distributed borehole flowmeter can be created from armored Fiber Optic cables with the Active-Distributed Temperature Sensing (A-DTS) method. The principle is that in a flowing fluid, the difference in temperature between a heated and unheated cable is a function of the fluid velocity. We outline the physical basis of the methodology and report on the deployment of a prototype A-DTS flowmeter in a fractured rock aquifer. With this design, an increase in flow velocity from 0.01 to 0.3 m s⁻¹ elicited a 2.5°C cooling effect. It is envisaged that with further development this method will have applications where point measurements of borehole vertical flow do not fully capture combined spatiotemporal dynamics.Keywords: Flowmeter, Fiber optics, Heated, A-DTS, BoreholeKeywords: Flowmeter, Fiber optics, Heated, A-DTS, Borehol

SelkerJohnBioEcoEngineeringActive-DistributedTemperature.pdf

We show how a distributed borehole flowmeter can be created from armored Fiber Optic cables with the Active-Distributed Temperature Sensing (A-DTS) method. The principle is that in a flowing fluid, the difference in temperature between a heated and unheated cable is a function of the fluid velocity. We outline the physical basis of the methodology and report on the deployment of a prototype A-DTS flowmeter in a fractured rock aquifer. With this design, an increase in flow velocity from 0.01 to 0.3 m s⁻¹ elicited a 2.5°C cooling effect. It is envisaged that with further development this method will have applications where point measurements of borehole vertical flow do not fully capture combined spatiotemporal dynamics.Keywords: Heated, Fiber optics, Borehole, Flowmeter, A-DTSKeywords: Heated, Fiber optics, Borehole, Flowmeter, A-DT