摘要:

Most hydrological phenomena in a specific region are, in general, non-homogeneous processes; such is the case of rainfall in the Basque Country of northern Spain. An analysis of precipitation events occurring there permits identification of different regions according to the mean storm occurrence rate and the mean number of storms per unit volume of precipitation. In this paper, a model of regional precipitation (Todorovic, 1967; Llamas, 1986) is applied to the Basque Country using recorded daily precipitation greater than 1 mm. The precipitation parameters mentioned above reveal two distinct pluviometrie regions.

ISSN:0262-6667    

DOI:10.1080/02626669509491416

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In 1988, the US Geological Survey began a study of the effects of potential climate change on the water resources of the Gunnison River basin. The Gunnison River, in southwestern Colorado, is an important tributary of the Colorado River, contributing approximately 40% of the flow of the Colorado River at the Colorado/Utah stateline. As part of the study, the sensitivity of annual and seasonal runoff in the East River basin, a sub-basin of the Gunnison River basin, to changes in temperature and precipitation was examined. To perform the sensitivity analyses, hypothetical climate changes were used to alter current time series of temperature and precipitation. The altered time series were then used as inputs to a hydrological model that translated these inputs into estimates of runoff. Mean annual and seasonal runoff resulting from a range of hypothetical climate changes were compared and evaluated. Results indicated that in general, changes in precipitation had a larger effect on changes in runoff than did changes in temperature. Changes in precipitation had significant effects on runoff during all seasons. Changes in temperature primarily affected the temporal distribution of runoff through the year. Changes in temperature affected the timing of snowmelt and the ratio of rain to snow, and therefore the effects of temperature were particularly significant during the spring and summer seasons. On an annual basis, increases in temperature led only to slight decreases in runoff. Results also indicated that the effects of an increase in mean annual temperature of 4°C on annual runoff could be offset by an increase in annual precipitation of between 4 and 5%, and that the magnitude of natural climatic variability was large and might mask the effects of long term climate changes.

ISSN:0262-6667    

DOI:10.1080/02626669509491417

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The total pools and chemical species of Fe in soils from seven groundwater/surface water ecotones were analysed. The associated soil waters from four of the sites were analysed for Fe and SO4. The selected sites were mainly the upper reaches of streams in coniferous forests, having a size of 3–4 m2. The results showed great differences in total Fe concentrations in the soils. The high positive correlation between pyrophosphate- extractable Fe and organic matter (Spearman rank coefficient 0.700) indicated the importance of organic C for the retention of Fe. Organically-bound Fe and Fe oxides were the major species in all the soils. Moreover, soil water analyses suggested that sulphate reduction occurs, with the formation of Fe-sulphides during seasons with high microbiological activity. Comparable sulphate concentrations in groundwater and runoff waters, but much lower concentrations in peat waters, may be a result of a dynamic cycling of reduction and oxidation within the soils. Another explanation could be that most of the discharging groundwater was flowing quickly through more permeable sections of the soil.

ISSN:0262-6667    

DOI:10.1080/02626669509491418

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Many recent researchers have ventured a physical modelling of mean areal precipitation with a view to ensuring an appropriate analysis of climate change. Preliminary results of a simple, practical and dynamic integration method of incomplete daily precipitation data for a mountainous catchment are presented here. This is a combinatorial technique of the Thiessen method and precipitation gauge availability. The estimated catchment precipitation is corrected for elevation variations. This double technique preserves, to a large extent, the physical structure of precipitation information which is vital for climate change interpretation. Furthermore, the proposed method can handle successfully any change in the gauge network, the greatest limitation of the inflexible Thiessen method.

ISSN:0262-6667    

DOI:10.1080/02626669509491419

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A fracture map is an essential aid in the study of fissured aquifers even though it often includes covered areas where the fractures are not visible. Is it possible to predict fracturing or permeable zones under the cover? This problem is dealt with using a stochastic approach based on fracture density. Classical methods of fracture density assessment involve several biases and are not adapted to hydrogeology. A proposed “fracture density index” (FDI) eliminates these biases and gives weight to two important parameters influencing the hydraulic conductivity of a zone: length and proximity of long fractures. The FDI is a regionalized variable and allows one to make predictions by kriging over covered zones. The proposed method has been applied to the Campoussy site (Pyrénées Orientales, France). In contrast to previous methods, the FDI predictions were in good agreement with the apparent hydraulic transmissivity and electrical anisotropy. The results were promising but the method needs to be tested on other sites before being considered a useful and efficient hydrogeological tool.

ISSN:0262-6667    

DOI:10.1080/02626669509491420

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Estimation of direct runoff volume and peak runoff rates for small rural catchments in Kenya, East Africa, poses a problem in view of the limited gauged data available. The problem can be circumvented by adopting a modelling approach. This, however, does require some base data for model calibration and validation. A highly reliable data base for two small catchments, Sambret (7.02 km2) and Lagan (5.44 km2), for nearly 22 years (1958–1980) is used in the present study. These catchments lie in the headwaters of the Lake Victoria drainage basin in Kenya and were intensively instrumented by the former East African Agricultural and Forestry Research Organisation (EAAFRO). In the Sambret catchment, 41 rainfall-runoff events were available, out of which 25 were used for model calibration while the other 16 were used for validation. To further verify the applicability of the models to different catchments, 18 events from the neighbouring Lagan catchment were also used. The SCS curve number procedure proposed by the United States Soil Conservation Service was used to estimate the direct runoff volumes. The curve numbers were derived from storm rainfall-runoff relationships and the results obtained were satisfactory. Peak runoff rates were derived by both Nash and kinematic wave models for the estimated runoff volumes. The Nash model gave acceptable results in both Sambret and Lagan. The kinematic wave model performed well in Sambret only; in Lagan, it under-predicted the peak runoff rates.

ISSN:0262-6667    

DOI:10.1080/02626669509491421

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Models are proposed to extend the monthly streamflow data at a site where the available historic rainfall and streamflow data are too short for adequate systems study, subject to the condition that there are no gauging sites in the basin or adjacent basins with a longer period of streamflow data. Hence rainfall data of a nearby raingauge station are used. Five regression models, namely, runoff coefficient model, single linear regression, monthly linear regression, monthly linear regression with stochastic description for residuals, and a double regressed model are used. The results show that the monthly linear regression model with stochastic description for the residuals is best suited for the purpose when applied to a case study.

ISSN:0262-6667    

DOI:10.1080/02626669509491422

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The effects of different land uses,vizagriculture, grassland and afforestation, were evaluated in comparison with untreated ravine waste land in ustifluvent soil susceptible to gully erosion under a semiarid climate. The infiltration was measured with constant head double ring infiltrometers. Saturated hydraulic conductivities for the study sites were computed with a clay based equation and a texture based equation. The difference between the final infiltration rate (after 180 min) and the saturated hydraulic conductivity was taken to be the effect of different land uses on the infiltration characteristics of the sites. The saturated hydraulic conductivities (Ks) calculated by the two methods were comparable for loamy sand soil. The twoKsvalues were different for sandy loam soil. The ravine proper and farming up and down cultivation practice under grazing and trampling etc. were found to have suppressed the infiltration rate. Agricultural land use on terraces showed a marginal increase. Thus, the study demonstrated a way of isolating the effect of different land uses using a simple method for the estimation of saturated hydraulic conductivity for ustifluvent soils. For structure-dominated soils a more precise determination of saturated hydraulic conductivity will be necessary.

ISSN:0262-6667    

DOI:10.1080/02626669509491423

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A heat transport model that incorporates the effect of decreases in hydraulic head due to pumping of groundwater has been developed to explain the decrease in groundwater temperature during the last three decades in the Nara basin, Japan. Vertical two-dimensional temperature analyses have been made based on a theory of simultaneous transfer of heat and water in porous media. The calculated relationships between the depth and the groundwater temperature in the discharge area agree well with the observed temperature-depth relationships. The model used suggests that the decrease in groundwater temperature is caused by the decrease in the hydraulic head due to pumping.

ISSN:0262-6667    

DOI:10.1080/02626669509491424

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626669509491425

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor