摘要:

Two topographically similar adjacent catchments near Johannesburg, South Africa, one suburban, the other natural grassland, were monitored over a five year period to detect differences in runoff and hydrological balance. A network of raingauges, boreholes, flow gauges and water meters was installed. Evapotranspiration was modelled using observed weather data. Groundwater was estimated from tracer and other borehole tests. Surface runoff from the undeveloped and suburban catchments was 4% and 15% of rainfall respectively. Evapotranspiration was 63% of rainfall for both catchments. Sewage outflow was 83% of water consumption for the suburban catchment. Little change in water table level occurred in the suburban catchment, and garden watering probably balanced the high evaporation. Piped water supply was 16% of the precipitation on the catchment.

ISSN:0262-6667    

DOI:10.1080/02626669409492751

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A brief review of research in remote sensing of water resources indicates that there are many positive results, and some techniques have been applied operationally. Currently, remote sensing data are being used operationally in precipitation estimates, soil moisture measurements for irrigation scheduling, snow water equivalent and snow cover extent assessments, seasonal and short term snowmelt runoff forecasts, and surface water inventories. In the next decade other operational applications are likely using remote measurements of land cover, sediment loads, erosion, groundwater, and areal inputs to hydrological models. Many research challenges remain, and significant progress is expected in areas like albedo measurements, energy budgets, and evapotranspiration estimation. The research in remote sensing and water resources also has much relevance for related studies of climate change and global habitability.

ISSN:0262-6667    

DOI:10.1080/02626669409492752

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Rainfall and runoff depths were analysed for 47 storms recorded on three urban drainage basins in Canberra, Australia. Three runoff mechanisms have been identified: runoff generated on effective impervious surfaces in all storms; runoff from pervious areas of small storage capacity during both large and small storms; and runoff from pervious areas of large storage capacity for larger storms. The data indicate that pervious surface runoff is generated on only a small part of the total basin area.

ISSN:0262-6667    

DOI:10.1080/02626669409492753

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Evapotranspiration of irrigated crops on two irrigation service areas along the lower Colorado River was estimated using a normalized difference vegetation index of satellite data. A procedure was developed which equated the index to crop coefficients. Evapotranspiration estimates for fields for three dates of thematic mapper data were highly correlated with ground estimates. Service area estimates using thematic mapper and Advanced Very High Resolution Radiometer data agreed well with estimates based on US Geological Survey gauging station data.

ISSN:0262-6667    

DOI:10.1080/02626669409492754

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In the absence of long-term records of sediment transport by UK rivers, sediment deposits in lakes and reservoirs offer considerable potential for estimating sediment yields and reconstructing changing patterns of sediment yield and sediment sources during the past century in response to environmental change. An investigation of the sediment deposits within the Old Mill Reservoir, located in the East Hams region of South Devon, UK, has shown that suspended sediment yields from the 1.58 km2catchment have averagedca.54 t km−2year−1over the period 1942 to 1991. Bedload transport from the catchment during the same period averaged 15 t km−2year−1. The sediment record also provided evidence of increasing productivity in the reservoir during recent years and of the impact of a single extreme event. The availability of several dateable horizons within the sediment cores made it possible to subdivide further the reconstructed record of sediment yield into four periods. This subdivision indicated that suspended sediment yields have increased more than fourfold since the Second World War from about 20 t km−2year−1toca.90 t km−2year−1. A variety of sediment properties, including mineral magnetic characteristics and caesium-137 activity, was used to fingerprint the dominant source of the deposited sediment. This fingerprint analysis indicated that, with the exception of the extreme event, the sediment sources have remained essentially constant throughout the period of record and that surface material from pasture areas represented the dominant source. The increase of suspended sediment yields during the postwar period was attributed to increased livestock numbers and grazing intensity in the catchment of the reservoir.

ISSN:0262-6667    

DOI:10.1080/02626669409492755

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The object of this paper is to discuss, using the example of the upper basin of the Garonne river, the conditions of use of radar for the measurement of precipitation in order to forecast floods in areas with substantial relief and a cold season, which is the case for most French basins. The principle of radar measurement of precipitation fields is summarily expounded and the factors influencing the quality of these measurements are presented, notably those in relation to the relief and climatology of precipitation and to the 0°C isotherm (precipitation melting level). The main difficulty is that, at mid-latitudes, the precipitation melting layer (i.e. the 0°C isotherm) is located at low altitude, which implies that, except in summer, radar does not observe a homogeneous scattering environmentviz.rain or snow. Most of the time, the radar beam reaches, at a short distance, the altitude of the upper limit of the rain. This problem is made worse in mountainous areas because, for the azimuthal sweeping of the radar beam, significant elevation angles need to be used in order to avoid ground echoes.

ISSN:0262-6667    

DOI:10.1080/02626669409492756

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

An improved parameter estimation procedure has been developed by using optimization techniques and applied to estimate the parameters of the log-Pearson type 3 (LP3) distribution. As a result, an improved estimation method was found. The new methods estimates the mean and the standard deviation of the log-transformed data by the method of moments and estimates the coefficient of skewness by minimizing both the relative root average square error (RRASE) and the relative average bias (RAB). Monte Carlo simulation was conducted for four selected LP3 populations. As compared with the method of moments, larger reductions in standard root mean square error (SRMSE) and standard bias (SBIAS) for quantile prediction can be achieved by the new method for small sample sizes and large return periods of quantiles. In addition, the new method can always fit the observed data better than the method of moments.

ISSN:0262-6667    

DOI:10.1080/02626669409492757

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626669409492758

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626669409492759

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626669409492760

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor