scholarly journals Analysing river network dynamics and active length - discharge relationship using water presence sensors

2021 ◽  
Author(s):  
Francesca Zanetti ◽  
Nicola Durighetto ◽  
Filippo Vingiani ◽  
Gianluca Botter
Keyword(s):  
Power Law ◽  
Cross Sections ◽  
Temporal Dynamics ◽  
River Network ◽  
Low Flow ◽  
Stream Network ◽  
Entire Study ◽  
Temporary Streams ◽  
Active Length ◽  
Spatio Temporal

Abstract. Despite the importance of temporary streams for the provision of key ecosystem services, their experimental monitoring remains challenging because of the practical difficulties in performing accurate high-frequency surveys of the flowing portion of river networks. In this study, about 30 electrical resistance (ER) sensors were deployed in a high relief 2.6 km2 catchment of the Italian Alps to monitor the spatio-temporal dynamics of the active river network during the fall of 2019. The set-up of the ER sensors was personalized to make them more flexible for the deployment in the field and more accurate under low flow conditions. Available ER data were analyzed, compared to field based estimates of the nodes' persistency and then used to generate a sequence of maps representing the active reaches of the stream network with a sub-daily temporal resolution. This allowed a proper estimate of the joint variations of active river network length (L) and catchment discharge (Q) during the entire study period. Our analysis revealed a high cross-correlation between the statistics of individual ER signals and the flow persistencies of the cross sections where the sensors were placed. The observed spatial and temporal dynamics of the actively flowing channels also revealed the diversity of the hydrological behaviour of distinct zones of the study catchment, which was attributed to differences in the catchment geology and stream-bed composition. The more pronounced responsiveness of the total active length to small precipitation events as compared to the catchment discharge led to important hysteresis in the L vs. Q relationship, thereby impairing the performances of a power-law model frequently used in the literature to relate these two quantities. Consequently, in our study site the adoption of a unique power-law L-Q relationship to infer flowing length variability from observed discharges would underestimate the actual variations of L by 40%. Our work emphasizes the potential of ER sensors for analysing spatio-temporal dynamics of active channels in temporary streams, discussing the major limitations of this type of technology emerging from the specific application presented herein.

scholarly journals Effects of Initial Epidemic Conditions, Sporulation Rate, and Spore Dispersal Gradient on the Spatio-Temporal Dynamics of Plant Disease Epidemics

1998 ◽  
Vol 88 (10) ◽  
pp. 1000-1012 ◽  
Author(s):  
X.-M. Xu ◽  
M. S. Ridout
Keyword(s):  
Spatial Pattern ◽  
Power Law ◽  
Temporal Dynamics ◽  
Initial Conditions ◽  
Disease Incidence ◽  
Disease Status ◽  
Spatio Temporal ◽  
Disease Epidemics ◽  
Sporulation Rate ◽  
The Relationship

A stochastic model that simulates the spread of disease over space and time was developed to study the effects of initial epidemic conditions (number of initial inocula and their spatial pattern), sporulation rate, and spore dispersal gradient on the spatio-temporal dynamics of plant disease epidemics. The spatial spread of disease was simulated using a half-Cauchy distribution with median dispersal distance μ (units of distance). The rate of temporal increase in disease incidence (βI, per day) was influenced jointly by μ and by the sporulation rate λ (spores per lesion per day). The relationship between βI and μ was nonlinear: the increase in βI with increasing μ was greatest when μ was small (i.e., when the dispersal gradient was steep). The rate of temporal increase in disease severity of diseased plants (βS) was affected mainly by λ: βS increased directly with increasing λ. Intraclass correlation (κt), the correlation of disease status of plants within quadrats, increased initially with disease incidence, reached a peak, and then declined as disease incidence approached 1.0. This relationship was well described by a power-law model that is consistent with the binary form of the variance power law. The amplitude of the model relating κt to disease incidence was affected mainly by μ: κt decreased with increasing μ. The shape of the curve was affected mainly by initial conditions, especially the spatial pattern of the initial inocula. Generally, the relationship of spatial autocorrelation (ρt,k), the correlation of disease status of plants at various distances apart, to disease incidence and distance was well described by a four-parameter power-law model. ρt,k increased with disease incidence to a maximum and then declined at higher values of disease incidence, in agreement with a power-law relationship. The amplitude of ρt,k was determined mainly by initial conditions and by μ: ρt,k decreased with increasing μ and was lower for regular patterns of initial inocula. The shape of the ρt,k curve was affected mainly by initial conditions, especially the spatial pattern of the initial inocula. At any level of disease incidence, autocorrelation declined exponentially with spatial lag; the degree of this decline was determined mainly by μ: it was steeper with decreasing μ.

scholarly journals Dynamique spatio-temporelle de l’occupation des sols des communes de Torodi, Gothèye et Tagazar de la région de Tillabéry au Niger

2020 ◽  
Vol 14 (3) ◽  
pp. 949-965
Author(s):  
Ibrahim Biga ◽  
Abdou Amani ◽  
Idrissa Soumana ◽  
Mourtala Bachir ◽  
Ali Mahamane
Keyword(s):  
Land Use ◽  
Temporal Dynamics ◽  
Landsat Images ◽  
Entire Study ◽  
Energy Wood ◽  
Spatio Temporal ◽  
Sentinel 2A ◽  
Bodies Of Water ◽  
Entire Study Area ◽  
Land Use Maps

L’homme à travers ses actions dénature fortement l’occupation des sols engendrant une modification du milieu naturel. Cet impact rend la nécessité de fournir aux autorités communales les cartes d’occupations des sols et des informations relatives à leurs état et dynamique. C’est dans cette optique qu’une étude de l’occupation des sols a été conduite dans trois communes de l’Ouest Nigérien. Elle a pour objectif de cartographier et d’analyser la dynamique de l’occupation des sols de ces communes à partir des images Landsat de 1984 et 2000 et celles de sentinelle 2A de 2017. La classification supervisée par maximum de vraisemblance a été appliquée et la dynamique a été analysée à partir des courbes et des calculs de superficies. Les résultats cartographiques ont permis l’établissement des cartes d’occupation des sols par commune. L’analyse de la dynamique de l’occupation des sols montre que les superficies des formations végétales et les jachères régressent sur l’ensemble de la zone d’étude. Les cultures et bâtis progressent respectivement de 180,96% et 119, 81% à Torodi, 65,69% et 205,42% à Tagazar et 98,82% et 143,15% à Gothèye. IL en est de même pour les zones dégradées et les plans d’eau qui connaissent des progressions et des régressions sur l’ensemble de la zone d’étude. Les L’agriculture, l’exploitation du bois d’énergie et la démographie sont les principaux facteurs de dégradation et de mutation du paysage. Ces résultats peuvent servir de base pour définir les zones prioritaires en vue de la restauration des zones dégradées et l’aménagement des formations naturelles.Mots clés : Télédétection, SIG, Cartographie, dégradation.   English Title: Spatio-temporal dynamics of the land use of Torodi, Gothèye and Tagazar township in the Tillabery region of NigerMan through his actions strongly distorts the use of land, causing a change in the natural environment. This impact makes it necessary to provide municipalities with land use maps and information relating to their condition and dynamics. It is with this in mind that a study of land use was carried out in three communes in western Niger. Its objective is to map and analyze the dynamics of the land use of these municipalities from the Landsat images of 1984 and 2000 and those of sentinel 2A from 2017. The supervised classification by maximum likelihood was applied and the dynamics was analyzed from curves and area calculations. The cartographic results made it possible to draw up land use maps by municipality. Analysis of the dynamics of land use shows that the areas of plant formations and fallows are declining over the entire study area. Crops and buildings rose respectively by 180.96% and 119, 81% in Torodi, 65.69% and 205.42% in Tagazar and 98.82% and 143.15% in Gothèye. The same is true for degraded areas and bodies of water which are experiencing increases and regressions over the entire study area. Agriculture, the exploitation of energy wood and demography are the main factors of degradation and mutation of the landscape. These results could serve as a basis for defining priority intervention areas for the restoration of degraded areas and the management of agroforestry forests and parks. Keywords: Remote sensing, GIS, Cartography, degradation.  

scholarly journals Technical Note: Cost-efficient approaches to measure carbon dioxide (CO<sub>2</sub>) fluxes and concentrations in terrestrial and aquatic environments using mini loggers

2015 ◽  
Vol 12 (3) ◽  
pp. 2357-2380 ◽  
Author(s):  
D. Bastviken ◽  
I. Sundgren ◽  
S. Natchimuthu ◽  
H. Reyier ◽  
M. Gålfalk
Keyword(s):  
Temporal Dynamics ◽  
Co2 Flux ◽  
Technical Note ◽  
Aquatic Environments ◽  
Co2 Fluxes ◽  
Stream Network ◽  
Co2 Concentrations ◽  
Direct Measurements ◽  
Spatio Temporal ◽  
Global Carbon

Abstract. Fluxes of CO2 are important for our understanding of the global carbon cycle and greenhouse gas balances. Several significant CO2 fluxes in nature may still be neglected as illustrated by recent findings of high CO2 emissions from aquatic environments, previously not recognized in global carbon balances. Therefore it is important to develop convenient and affordable ways to measure CO2 in many types of environments. At present, direct measurements of CO2 fluxes from soils or waters, or CO2 concentrations in surface water, are typically labour intensive or require costly equipment. We here present an approach with measurement units based on small inexpensive CO2 loggers, originally made for indoor air quality monitoring, that were tested and adapted for field use. Measurements of soil–atmosphere and lake–atmosphere fluxes, as well as of spatio-temporal dynamics of water CO2 concentrations (expressed as the equivalent partial pressure, pCO2aq) in lakes and a stream network are provided as examples. Results from all these examples indicate that this approach can provide a cost- and labor efficient alternative for direct measurements and monitoring of CO2 flux and pCO2aq in terrestrial and aquatic environments.

scholarly journals Connectivity of Ephemeral and Intermittent Streams in a Subtropical Atlantic Forest Headwater Catchment

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1526
Author(s):  
Alondra B. A. Perez ◽  
Camyla Innocente dos Santos ◽  
João H. M. Sá ◽  
Pedro F. Arienti ◽  
Pedro L. B. Chaffe
Keyword(s):  
Overland Flow ◽  
Soil Depth ◽  
Low Cost ◽  
Intermittent Flow ◽  
Runoff Generation ◽  
Stream Network ◽  
Temporary Streams ◽  
Active Length ◽  
The Impact ◽  
Headwater Catchment

Stream network extension and contraction depend on landscape features and the characteristics of precipitation events. Although this dependency is widely recognized, the interaction among overland-flow generation processes, drainage active length, and frequency in temporary streams remains less understood. We studied a forest headwater catchment with wide variation in soil depth to investigate the runoff generation processes that lead to the occurrence of ephemeral and intermittent flow and connectivity between hillslope and outlet. We used low-cost equipment to monitor the variation in the length of the active drainage network and to measure the water table development. The flow in the channels can develop even under light rainfall conditions, while the connectivity is controlled by antecedent wetness, total precipitation, and active contribution area thresholds. Runoff permanence and fragmentation were related to soil depth variation; flow being usually more disconnected due to deeper water tables in deeper soil locations. Our findings emphasized the impact of soil structure on runoff generation in hillslopes and can be useful in the management of the most active areas and their impact on the quality of available water.

Spatial and temporal dynamics of Pacific capelin Mallotus catervarius in the Gulf of Alaska: implications for ecosystem-based fisheries management

2020 ◽  
Vol 637 ◽  
pp. 117-140 ◽  
Author(s):  
DW McGowan ◽  
ED Goldstein ◽  
ML Arimitsu ◽  
AL Deary ◽  
O Ormseth ◽  
...  
Keyword(s):  
Temporal Dynamics ◽  
Marine Ecosystem ◽  
Gulf Of Alaska ◽  
Data Series ◽  
Limited Information ◽  
Important Species ◽  
Multiple Data ◽  
Spatial And Temporal Dynamics ◽  
Spawning Areas ◽  
Spatio Temporal

Pacific capelin Mallotus catervarius are planktivorous small pelagic fish that serve an intermediate trophic role in marine food webs. Due to the lack of a directed fishery or monitoring of capelin in the Northeast Pacific, limited information is available on their distribution and abundance, and how spatio-temporal fluctuations in capelin density affect their availability as prey. To provide information on life history, spatial patterns, and population dynamics of capelin in the Gulf of Alaska (GOA), we modeled distributions of spawning habitat and larval dispersal, and synthesized spatially indexed data from multiple independent sources from 1996 to 2016. Potential capelin spawning areas were broadly distributed across the GOA. Models of larval drift show the GOA’s advective circulation patterns disperse capelin larvae over the continental shelf and upper slope, indicating potential connections between spawning areas and observed offshore distributions that are influenced by the location and timing of spawning. Spatial overlap in composite distributions of larval and age-1+ fish was used to identify core areas where capelin consistently occur and concentrate. Capelin primarily occupy shelf waters near the Kodiak Archipelago, and are patchily distributed across the GOA shelf and inshore waters. Interannual variations in abundance along with spatio-temporal differences in density indicate that the availability of capelin to predators and monitoring surveys is highly variable in the GOA. We demonstrate that the limitations of individual data series can be compensated for by integrating multiple data sources to monitor fluctuations in distributions and abundance trends of an ecologically important species across a large marine ecosystem.

Sign in / Sign up

Export Citation Format

Share Document