摘要:

AbstractInterception loss, I, was determined by continuous concurrent measurements of the canopy precipitation balances of a mature seed orchard tree ofPinus radiata, and a dominant tree ofEucalyptus viminalisat a mountainous high rainfall site (900 m a.s.l.) in Tallaganda State Forest of the Upper Shoalhaven Catchment. Approximate canopy storage capacity (Sc) of the pine was 54 l, and that of the eucalypt was 11·3 l. Gross pineIwas 26·5 per cent and eucalyptIwas 8·3 per cent of total incident rainfall over a period of 18 months, from June 1975 to December 1976. The exponential model that provided the best fit to overall data relatingIto gross rainfall (Pg) was of good precision for the pine (r2= 0·73) but rather poor precision for the eucalypt (r2= 0·27). A consistent pattern in interception data of the two canopy types suggested that variation inIwas related to change in pervasive conditions influencing rates of evaporation from wet canopies during rainfall. Multiple regression analyses confirmed that factors such as rainfall intensity and windspeed explained some of the variation in eucalyptIbut little in pineI.Negative eucalyptIand corresponding low values of pineIover a wide range ofPg(up to 20 mm) suggest that capture of wind‐borne precipitation (cloud, mist, or fog) had also complicated the canopy precipitation ba

ISSN:0885-6087    

DOI:10.1002/hyp.3360050202

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractAnalyses were made of the concurrent canopy precipitation balances of a seed orchard pine and a mature forest eucalypt during protracted rainfalls selected for their representativeness of the range of variation encountered in the two canopy types at Tallanganda State Forest (ca.990 m a.s.l.) in the Upper Shoalhaven Valley of southeastern New South Wales. Although their canopy storage capacities were widely different there was consistent interception behaviour in the pine and the eucalypt in all events. Detailed weather data and the time courses of interception loss provided circumstantial evidence for a varying and, at times, substantial influence of cloud or mist deposition on the canopy precipitation balances during rainfall that made a significant contribution to the variation in rainfall interception data. Mean evaporation rates from the saturated canopies during rainfall varied from −0·02 mm hr−1up to 0·68 mm hr−1in the pine; and from −0·04 mm hr−1up to 0·13 mm hr−1in the eucalypt. The implications of cloud‐capture during rainfall for studies of rainfall interception in forests of southeastern Austra

ISSN:0885-6087    

DOI:10.1002/hyp.3360050203

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractSoil water regimes and water balances are presented for a series of drained and undrained experimental grassland plots, intended to examine the agronomic consequences of drainage. Although drainage has lowered the watertables and reduced the duration of waterlogging in the drained plots, its effects in terms either of the total water quantities leaving the site or of peak flows is quite small. The major effect of drainage is to alter the route of water loss from the site. In its undrained state, the soil is waterlogged for the majority of the winter, incident rainfall cannot infiltrate, and water leaves as surface runoff or near‐surface flow. The introduction of fissures by mole drainage both provides an outlet and enhances the macroporosity, so that the rain moves rapidly through the soil and appears as drainflow. Consequently, the additional delay in generating peak runoff through the drainage system is only of the order of 30 minutes on this sit

ISSN:0885-6087    

DOI:10.1002/hyp.3360050204

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractPrevious discussions of the catastrophic drainage of ice‐dammed lakes have centred on mechanisms where characteristics of the lake are crucial to drainage initiation, for example dam flotation or tunnel formation at a critical lake depth. This paper describes a mechanism for lake drainage where drainage initiation depends on the characteristics of the glacier and is independent of the characteristics of the lake. Prediction of this mechanism must be based on glacier dynamics, whereas the mechanisms most commonly discussed previously are best predicted primarily on the basis of lake evolution.An ice‐dammed lake at the margin of the glacier Solheimajokull, in southern Iceland, was observed to drain rapidly into the sub‐ or englacial drainage system, supplying water and debris to the bed or interior of the glacier. Geomorphological evidence suggests that the lake drains and refills periodically, discharging up to 13300 m3of water into the glacier‐hydrological system. The depth of the maximum lake is insufficient to cause either flotation of the ice margin or tunnel opening by plastic deformation of the ice, and we suggest that sudden drainage is related to ice‐bed separations associated with specific glacier flow states rather than to a critical lake depth threshold. This mechanism of lake drainage has implications for conditions at the glacier bed, for the development of basal ice and for the entrainment of debris into the glacier, as well as for the prediction of potentially hazardous catastrophic drainage events and jokulhlaups from ice‐d

ISSN:0885-6087    

DOI:10.1002/hyp.3360050205

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractCurrent conceptual runoff models hypothesize that stormflow generation on the Canadian Shield is a combination of subsurface stormflow and saturation overland flow. This concept was tested during spring runoff in a small (3.3 ha) headwater basin using: (1) isotopic and chemical hydrograph separation and (2) field mapping and direct tracing of saturated areas. Isotopic and chemical hydrograph separation indicated three runoff components: (1) pre‐melt subsurface flow; (2) subsurface flow of new (event) water; and (3) direct precipitation on to saturated areas (DPS). During early thaw‐freeze cycles, their relative contributions to total flow remained constant (65 per cent, 30 per cent, and 5 per cent respectively). It is hypothesized that lateral flow along the bedrock/mineral soil interface, possibly through macropores, supplied large volumes of subsurface flow (of both old and new water) rapidly to the stream channel. Much higher contributions of DPS were observed during an intensive rain‐on‐snow event (15 per cent of total flow). Mapping and direct tracing of saturated areas using lithium bromide, suggested that saturated area size was positively correlated to stream discharge but its response lagged behind that of discharge. These observations suggest that the runoff mechanisms, and hence the sources of stream flow, will vary depending on storm characte

ISSN:0885-6087    

DOI:10.1002/hyp.3360050206

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe use of a single‐bowl continuous‐flow centrifuge (CFC, Sharples‐Pennwalt Model AS‐12) for dewatering suspended sediment from large volumes of river water is evaluated. Sediment‐recovery efficiency of 86‐91 per cent is comparable to that of other types of CFC units. The recovery efficiency is limited by the particle‐size distribution of the feed water and by the limiting particle diameter that is retained in the centrifuge bowl. The limiting particle diameter, using the parameters for this study (bowl radius = 10.5cm; bowl length = 71.1 cm; rotational velocity = 16000 r min−1; flow rate = 2 L min−1, and an assumed hydrated particle density = 1.7 gm cm−3), is 370 nm. There seems to be no particle‐size fractionation within the centrifuge bowl—the median particle size was the same at the top as at the bottom. Particle electrophoretic mobility plays some role in fractionation of particles within the centrifuge. The mobility ranged from −1.19 to −2.01 × 10−8m2V−1s−1, which is typical of clays coated with organic matter, the charge of which is partially neutralized by divalent cations and iron. Contamination by trace metals and organics is minimized by coating all surfaces that come in contact with the sample with either FEP or PFA Teflon and using a removable FEP Teflon liner in the centrifuge bowl. Because of the physical and chemical factors affecting particle fractionation within the centrifuge, care must be exercised in interpreting the environmental consequences of particles collected

ISSN:0885-6087    

DOI:10.1002/hyp.3360050207

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe137Cs radioactivity of soils was used as a tracer of soil erosion in a catchment in the Netherlands: 143 samples were analysed to map the137Cs redistribution using geostatistical interpolation methods. Caesium‐137 activities on grassland are significantly higher than on arable land. Also,137Cs activities on waning slopes are higher and activities on steep slopes are lower. The soil erosion estimates, derived from the137Cs data, are used to validate the USLE erosion model. The recent Chernobyl nuclear accident also contributed to the137Cs activity. However, the Chernobyl input of137Cs, with a constant ratio of 1.765:1 to134Cs, cannot be used as a tracer of soil erosion. Because of the rapid decay of134Cs, we will not be possible to separate the sources of137Cs in the near future in areas significantly influenced by Chernobyl fallout and in these areas137Cs can no longer be used as a soil erosion trace

ISSN:0885-6087    

DOI:10.1002/hyp.3360050208

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

ISSN:0885-6087    

DOI:10.1002/hyp.3360050201

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY