| 1. |
- Berndtsson, Ronny, et al.
(författare)
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Soil water, soil chemical and crop variations in a clay soil
- 1996
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 41:2, s. 171-178
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Tidskriftsartikel (refereegranskat)abstract
- Spatial properties of field soils vary in a complex manner. Especially in arid and semiarid areas, this variability affects plant quality and crop production. An experimental field plot was extensively sampled regarding soil water (378 gravimetrical samples), soil chemical content (314 samples), and crop yield and chemical content (26 samples) at the Cherfech agricultural field research station in Tunisia. Geostatistical analyses were made to gain a better understanding of the in situ variability of soil water, soil chemical and crop properties. Ranges of correlation were found to vary over distances between 5 and over 40 m. Nugget and sill values for semivariograms were almost an order of magnitude larger for crop samples compared to soil samples. The crop yield components appeared to have larger variability as compared to crop chemical components.
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| 2. |
- Semadeni Davies, Annette, et al.
(författare)
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Snowmelt sensitivity to radiation in the urban environment
- 1998
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 43:1, s. 67-89
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Tidskriftsartikel (refereegranskat)abstract
- Despite having the same snowmelt processes, snowpacks in urban environments experience a range of conditions different from those of rural areas. Melt is intensified at some sites due to greater radiative energy. Shading, however, can reduce radiation and melt at other sites. Changes to the radiation balance and snowpack processes have been investigated. A physical snowpack model was developed and tested against data from an impervious study plot in Sweden. Estimated surface runoff compared favourably with that measured. An urban radiation scheme captured the observed net allwave radiation well. Series of sensitivity analyses were made by perturbing the scheme to represent three urban locations: open ground and the southern (sunny) and north (shaded) sides of a hypothetical building. Cloudiness, albedo, wall temperature and sky view were altered to reproduce common urban conditions. Even without perturbation, the shaded and sunny sides of the building had different radiation fluxes-the south side experienced a daily average net radiation enhancement of 15 W m-2 and the north a decrease of 35 W m-2. This pattern was reflected in melt, perturbation exaggerated the disparity.
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| 3. |
- Uhlenbrook, Stefan, et al.
(författare)
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Prediction uncertainty of conceptual rainfall-runoff models caused by problems in identifying model parameters and structure
- 1999
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Ingår i: Hydrological Sciences Journal. - 0262-6667 .- 2150-3435. ; 44:5, s. 779-797
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Tidskriftsartikel (refereegranskat)abstract
- The uncertainties arising from the problem of identifying a representative model structure and model parameters in a conceptual rainfall-runoff model were investigated. A conceptual model, the HBV model; was applied to the mountainous Brugga basin (39.9 km(2)) in the Black Forest, southwestern Germany. In a first step, a Monte Carlo procedure with randomly generated parameter sets was used for calibration. For a ten-year calibration period, different parameter sets resulted in an equally good correspondence between observed and simulated runoff. A few parameters were well defined (i.e, best parameter values were within small ranges), but for most parameters good simulations were found with values varying over wide ranges. In a second step, model variants with different numbers of elevation and landuse zones and various runoff generation conceptualizations were tested. In some cases, representation of more spatial variability gave better simulations in term of discharge. However, good results could be obtained with different and even unrealistic concepts. The computation of design floods and low flow predictions illustrated that the parameter uncertainty and the uncertainty of identifying a unique best model variant have implications for model predictions. The flow predictions varied considerably. The peak discharge of a flood with a probability of 0.01 year(-1), for instance, varied from 40 to almost 60 mm day(-1). It was concluded that model predictions, particularly in applied studies, should be given as ranges rather than as single values.
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| 4. |
- Krasovskaia, I, et al.
(författare)
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Dimensionality of Scandinavian river flow regimes
- 1999
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Ingår i: HYDROLOGICAL SCIENCES JOURNAL-JOURNAL DES SCIENCES HYDROLOGIQUES. - : IAHS PRESS, INST HYDROLOGY. - 0262-6667. ; 44:5, s. 705-723
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A river flow regime describes an average seasonal behaviour of river flow, usually representing a set of long-term monthly mean values. Seasonal patterns of flow can be regular, repeating in principle the same pattern from year to year, or irregular, i.e.
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