223 research outputs found
Numerical Validation of a Diurnal Streamflow-Pattern-Based Evapotranspiration Estimation Method
The evapotranspiration (ET) estimation method by Gr
ibovszki et al. (2010b) has so far
been validated only at one catchment because good q
uality discharge time series with the required
high enough temporal resolution can probably be fou
nd at only a handful of watersheds worldwide. To
fill in the gap of measured data, synthetic groundw
ater discharge values were produced by a 2D finite
element model representing a small catchment. Geome
trical and soil physical parameters of the
numerical model were changed systematically and it
was checked how well the model reproduced the
prescribed ET time series. The tests corroborated t
hat the ET-estimation method is applicable for
catchments underlain by a shallow aquifer. The slop
e of the riparian zone has a strong impact on the
accuracy of the ET results when the slope is steep,
however, the method proved to be reliable for
gentle or horizontal riparian zone surfaces, which
are more typical in reality. Likewise, errors sligh
tly
increase with the decrease of riparian zone width,
and unless this width is comparable to the width of
the stream (the case of a narrow riparian zone), th
e ET estimates stay fairly accurate. The steepness
of
the valley slope had no significant effect on the r
esults but the increase of the stream width (over 4
m)
strongly influences the ET estimation results, so t
his method can only be used for small headwater
catchments. Finally, even a magnitude change in the
prescribed ET rates had only a small effect on the
estimation accuracy. The soil physical parameters,
however, strongly influence the accuracy of the
method. The model-prescribed ET values are recovere
d exactly only for the sandy-loam aquifer,
because only in this case was the model groundwater
flow system similar to the assumed, theoretical
one. For a low hydraulic conductivity aquifer (e.g.
clay, silt), root water uptake creates a considera
bly
depressed water table under the riparian zone, ther
efore the method underestimates the ET. In a sandy,
coarser aquifer the flow lines never become vertica
l even bellow the root zone, so the method
overestimates the ET rate, thus the estimated ET va
lues need to be corrected. Luckily the prescribed
and estimated ET rates express a very high linear c
orrelation, so the correction can be obtained by th
e
application of a constant, the value of which solel
y depends on soil type
Új direkt és inverz módszerek a nehézségi erőtér szintetikus modellezésében = New forward and inverse methods for the synthetic modelling of the gravity field
A kutatás során azt vizsgáltuk, hogy mikĂ©ppen lehet olyan lokális/regionális tömegeloszlási modellt lĂ©trehozni, amely alkalmas a nehĂ©zsĂ©gi tĂ©r tömegvonzási összetevĹ‘jĂ©nek (potenciál, gradiens vektor, Eötvös tenzor) a geodĂ©ziai számĂtásokhoz elegendĹ‘ pontosságĂş meghatározására. E cĂ©l elĂ©rĂ©sĂ©hez a modellbĹ‘l számĂthatĂł Newton-fĂ©le tömegvonzási hatásnak jĂłl kell illeszkednie a rendelkezĂ©sre állĂł mĂ©rĂ©si eredmĂ©nyekhez, amely feltĂ©tel az Ăşn. inverziĂłs feladat megoldásával teljesĂthetĹ‘. Ennek során egy valamilyen norma szerint (pl. L2) optimális sűrűsĂ©g eloszlás modell jön lĂ©tre, amelynek segĂtsĂ©gĂ©vel olyan erĹ‘tĂ©r paramĂ©tereket is analitikusan meghatározhatunk (direkt feladat), amelyeknek mĂ©rĂ©se esetleg nem is lehetsĂ©ges. InverziĂłra kifejlesztett megoldásainkban a derĂ©kszögű hasáb tĂ©rfogatelemet alkalmaztuk (Ă“falu, Dunaföldvár) Ă©s teszteltĂĽnk statisztikai vizsgálatokon alapulĂł iteratĂv algoritmusokat (Yilgarn craton, Australia). Az erĹ‘tĂ©r modelltĂ©ren kĂvĂĽli szimuláciĂłjához vizsgáltuk a vĂ©konyrĂ©teg modellek alkalmazhatĂłságát. RegularizáciĂłs mĂłdszerrel javĂtottuk az inverziĂłra felĂrt egyenlet-rendszer kondicionáltságát. A Kárpát-Pannon tĂ©rsĂ©g 3D kĂ©regmodelljĂ©nek leĂrásához alternatĂv megoldáskĂ©nt alkalmaztuk a polihedron tĂ©rfogatelemeket is. Ezek használata biztosĂtja mind a sűrűsĂ©g-határfelĂĽletek mind a földgörbĂĽlet geometriailag pontosabb követĂ©sĂ©t. A kifejlesztett számĂtási algoritmus kikĂĽszöböli a számĂtási pont Ă©s a tĂ©rfogatelem relatĂv helyzetĂ©bĹ‘l adĂłdĂł esetleges szingularitást. | During the present research the possibilities of the generation of local/regional mass models and their use for the simulation of gravity field parameters (potential, gradient vector, Eötvös tensor) to be applied in geodetic computations, were investigated. The required high precision needs good fit between the observed parameters and the Newtonian mass attraction response of the model. It can be provided by the solution of an inverse problem which results in an optimal density distribution according to a specific norm (e.g. L2). The model obtained by inversion can be used for the analytical forward computation of gravity field related parameters among them some are immeasurable. In the one-step solutions of the inversion problem rectangular volume elements (prisms) were applied on two areas (Ă“falu, Dunaföldvár) and iterative algorithms based on statistical analysis were also tested (Yilgarn craton, Australia). For the simulation of the gravitational field in the exterior of the source space discrete thin layer models were introduced. A regularization method was developed for the improvement of the condition of the equation system set up for thin layer inversion. Polyhedrons were applied in the modeling of the 3D crustal structure of the Carpathian-Pannonian region. Their use leads to better geometrical representation of density interfaces and the Earth's curvature than what is provided by prisms. The formal singularities of the polyhedron formulae are properly handled
ErdĹ‘sĂĽlt kisvĂzgyűjtĹ‘k hidrolĂłgiai Ă©s vĂzminĹ‘sĂ©gi jellemzĹ‘i = Hydrological and water quality charasteristics of forest covered catchments
A projekt a közel 20 Ă©ve folyamatosan működĹ‘ erdőállományok vĂzháztartásával kapcsolatos kutatásokat támogatta a Sopron melletti HidegvĂz-völgyben. A projekt keretĂ©ben a hidegvĂz-völgyi kĂsĂ©rleti vĂzgyűjtĹ‘ folyamatos működtetĂ©se mellett egyes meglĂ©vĹ‘ mĂ©rĂ©sek tĂ©rbeli Ă©s idĹ‘beli kiterjesztĂ©se törtĂ©nt meg, ill. Ăşj jellemzĹ‘k mĂ©rĂ©sĂ©t is beállĂtottuk. Az eddigi állományklĂma, intercepciĂł Ă©s lefolyásmĂ©rĂ©sek mellett vizsgáltuk az avarintercepciĂłt, a patakmenti talajvĂz Ă©s talajnedvessĂ©g változását, a növĂ©nyállományok folyamatos fenolĂłgiai Ă©s növekedĂ©svizsgálatával kiegĂ©szĂtve. Az eddigi mennyisĂ©gi mĂ©rĂ©sek mellett egyes fiziko-kĂ©miai alapmĂ©rĂ©seket rendszeresĂtettĂĽnk 1-2 automata adatgyűjtĹ‘vel idĹ‘ben is kiterjesztve a mĂ©rĂ©seket. A projekt egyik legnagyobb eredmĂ©nye az erdĂ©szeti hidrolĂłgia Ă©s az erdĂ©szeti vĂzgazdálkodás terĂ©n az erdĹ‘k evapotranszspiráciĂłjának számĂtására kidolgozott Ăşj mĂłdszer. A projektben rĂ©sztvevĹ‘ fiatal kutatĂłk a terepi, benti laboratĂłriumi Ă©s modellezĂ©si munkák során Ă©rtĂ©kes gyakorlati tapasztalatokat szereztek Ă©s kĂ©pessĂ© váltak a tudományterĂĽleten komoly tudományos eredmĂ©nyek elĂ©rĂ©sĂ©re Ă©s nemzetközi projektekben valĂł rĂ©szvĂ©telre. | This project contributed to the operation of the long term forest hydrological research in HidegvĂz Valley in the neighbourhood of Sopron. In the frame of this project in addition to the regular continuous working of earlier settled research activities (stand climate and interception measuring, runoff measurements) new attributes of forest hydrological cycle (forest litter interception, groundwater level and soil moisture, phenological state) has been started to measure. The earlier examined attributes measurements extended in spatial and in temporal scale also. In addition to the quantitative measurements, some basic water quality parameter has been started to measure with settling of some automatic sensors. New method is elaborated in the frame of this project, which will presumably widely used (because of its low cost demands and easy to use features). Moreover vegetation water use can be calculated with help of this novelty method more accurate than before. Young scientists, who took part of this project, gained a lot of experiences in field work, laboratory analysis and modelling. They became qualified experts in the theme of eco-hydrology and got ability to take part in international projects
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