| 1. |
- Bengtsson, Lars, et al.
(author)
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Water balance for landfills of different age
- 1994
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In: Journal of Hydrology. - 0022-1694 .- 1879-2707. ; 158:3-4, s. 203-217
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Journal article (peer-reviewed)abstract
- Water-related processes in landfills are discussed with emphasis on internal processes such as field capacity, moisture variation in time and space, and macropore flow. Runoff production and evaporation from landfills in Sweden of different age are investigated. It is clarified in what ways and for how long a closed municipal landfill differs from an ordinary land area from a hydrological point of view.
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| 2. |
- Johnsson, Holger, et al.
(author)
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Surface runoff and soil water percolation as affected by snow and soil frost
- 1991
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In: Journal of Hydrology. - 0022-1694 .- 1879-2707. ; 122:1-4, s. 141-159
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Journal article (peer-reviewed)abstract
- A coupled soil water and heat model was used to study the influence of soil frost and snow on infiltration and drainage flow in an agricultural field in central Sweden. An analogy between freezing/thawing and drying/wetting was assumed for the soil frost submodel. Model simulations were evaluated against measurements of total soil water content, unfrozen water content, soil temperature and drainage water-flow. The influences of soil frost and spatial variation in snow cover were studied by simulation of possible extreme situations in the field. The model accurately described the dynamics of soil temperature and water contents; however, infiltration and field drainage flow were considerably underestimated and delayed by about three weeks under frozen conditions. A model simulation, discounting the effects of soil frost, overestimated the drain response. An attempt at simulating the field variation in snow cover by assuming possible 'sink points' for snowmelt, explained part of the deviations between simulated and measured drain flows. A basis for a new model formulation of the infiltration and percolation processes in frozen soil is proposed in which two water-flow domains are assumed, one low-flow domain in the fine pores, smaller than those filled with ice, and one high-flow domain in the large air-filled pores. This allows the simulation of rapid infiltration in large ice-free pores and drainage flow under frozen conditions as well as the resulting redistribution of ice from smaller to larger pores.
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| 3. |
- Lundberg, Angela
(author)
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Evaporation of intercepted snow : review of existing and new measurement methods
- 1993
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In: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 151:2-4, s. 267-290
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Journal article (peer-reviewed)abstract
- Knowledge of the annual water balance within a catchment is still hampered by an insufficient understanding of winter conditions. The least known term of the winter water balance is evaporation - particularly that from intercepted snow. Methods to measure interception and evaporation are reviewed. Undisturbed meteorological conditions, high time resolution and continuous measurements of intercepted mass were taken as criteria for an ideal method. The ideal method should work during periods of melt and sublimation and above rough forest surfaces. None of the existing methods fulfils all the criteria. Most traditional hydrological methods to estimate winter-time evaporation, such as runoff and snow-course studies, non-weighing lysimeters, and precipitation and throughfall measurements, produce too little information to distinguish the causes of the observed changes. Among micrometeorological methods, only the eddy-correlation technique is suitable, and should be used in combination with interception measurements. Of the methods primarily designed to quantify interception, i.e. collection of intercepted snow, visual or photographic observations, displacement transducers, weighing of branches and trees and gamma-ray attenuation, only the last two yield continuous interception records. In combination with continuous measurements of throughfall and drip, these methods can be used to study the evaporation process. The gamma-ray method can be used to measure whole-canopy losses, whereas the other two methods deal only with losses from a branch or a single tree. The weighing-lysimeter technique produces the same information as the method of weighing a cut tree but employs a more complex set-up. The weighing-tree method combined with measurement of drip is one of the current methods that is most suitable for process studies. A new device for this purpose is presented, which differs from earlier designs by allowing a continuous weighing of drip in a tray of 2m width placed around the tree. The tray was fastened to the tree with wires and was automatically raised and lowered, thus allowing continuous measurements of both intercepted mass (with the tray raised) and evaported mass (with the tray lowered). A maximum evaporation rate of 0.3 mm h-1 was recorded with this device on 22-23 March 1990 at a site close to Luleå in northern Sweden. This maximum value was measured when wet snow was present, and confirmed earlier reports of high evaporation rates. The maximum evaporated mass during 24 h was 3.3 mm.
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| 4. |
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| 5. |
- Bengtsson, Lars, et al.
(author)
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Particle movement of melt water in a subdrained agricultural basin
- 1992
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In: Journal of Hydrology. - 0022-1694. ; 135:1-4, s. 383-398
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Journal article (peer-reviewed)abstract
- The pathways of melt water from a subdrained agricultural basin in southern Finland were investigated using oxygen-18 as tracer and measuring subdrainage water and total basin runoff. The flow paths for the melt water to reach the subdrains were through cracks in the ploughed layer and through regular spaced vertical sand-gravel drains. As long as the top soil was frozen a major part of the water that reached the agricultural basin outlet was snowmelt water. The basin runoff during the melt period 27 March- 1 3 April totalled 86 mm of which 20% was overland flow.
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| 6. |
- Berndtsson, Ronny, et al.
(author)
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Some Eulerian and Lagrangian statistical properties of rainfall at small space-time scales
- 1994
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In: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 153:1-4, s. 339-355
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Journal article (peer-reviewed)abstract
- Management of urban hydrological systems requires a knowledge of short-term and small-scale rainfall properties. Small catchment areas, dense building structures, a high degree of impermeable areas, and resulting rapid runoff, mean that the properties of individual rain cells are important considerations. Accordingly, this paper characterizes mainly spatial rainfall properties on a scale suitable for urban hydrology. Because of the usually dominant advective velocity component of individual rain cells the Eulerian view (observations of the moving rain cell by a fixed rain gage network) gives a distorted picture in the direction of movement of the actual rain cell. The extent of distortion depends on the magnitude of the advective velocity. The Lagrangian approach (moving along with the same speed and direction as the cell) gives different information regarding cell characteristics (e.g. size) compared with the Eulerian approach. It is shown that the Lagrangian cell size as indicated by the spatial correlation structure on average is twice the size of the Eulerian cell size. Thus, it is argued that the Lagrangian approach provides a more realistic picture of the rainfall structures compared with the Eulerian approach. The cell properties exhibit a temporal persistence of the spatial characteristics in the direction of movement. This persistence is, however, not strong and thus a forecasting procedure using advection only does not seem appropriate.
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| 7. |
- Olsson, Jonas, et al.
(author)
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An analysis of the rainfall time structure by box counting-some practical implications
- 1992
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In: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 137:1-4, s. 261-277
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Journal article (peer-reviewed)abstract
- The scale-invariant behavior of the rainfall time structure was investigated by applying the box counting method to rainfall time series. Two years of minute observations, 90 years of daily observations and 170 years of monthly observations were analyzed and the results were interpreted and related to physical properties of the rainfall process. This paper discusses the question of whether an hypothesis of temporal scale invariance is valid for rainfall and the possibilities of using it in practical hydrology.
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