Estimation of actual evaporation using precipitation and soil moisture records in arid climates     

A. U. Sorman  M. J. Abdulrazzak 《水文研究》1995,9(7):729-741

There is little knowledge available about infiltration and evaporation processes in wadi channels in arid regions. This work was conducted to determine the actual evaporation from bare soils in wadi channels in the south-western region of the Kingdom of Saudi Arabia. The estimation of soil evaporation is highly dependent on the availability of moisture in the upper layers of alluvial wadis, in which the areal rainfall, flood hydrograph and soil properties play a significant part. The study was conducted by estimating the actual evaporation using soil moisture data, precipitation and runoff depths in a representative basin. The results are compared with potential rates. The actual rates were 1.5 mm/day immediately after a rainy day and then decreased to 0.42 mm/day. The minimum rate was about 0.1–0.2 mm/day during the dry season. The potential rates were about 9.5 mm/day in June and July, decreasing to 3.5 mm/day in December and January.  相似文献   

Study on changes of plasmalemma permeability and some primary inorganic ions of Antarctic ice microalgae （Chlamydomonas sp. ICE-L） in the low-temperature stress     

郑洲  缪锦来陈豪张波涛  李光友 《极地研究(英文版)》2006,17(1):20-29

The changes of plasmalemma permeability and some primary inorganic ions of Antarctic ice microalgae （ Chlamydomonas sp. ICE-L） in the low-temperature stress were examined. The plasmalemma of 1CE-L could maintain the stability at the freezing condition of -6 ℃. That signifies that it could maintain the proper function of plasmalemma and stability of the intracellular environment during sea ice formation. The function of inorganic ions on low-temperature adaptation of ICE-L was investigated by using the X-ray microanalysis method. Low temperature （0 - -6 ℃ ） induces Ca^2 ＋ concentration increment of cytoplasm, but after 24 h the content decrease quickly to normal value. As a matter of fact, Ca^2 ＋ plays an important role as the second messenger in the low temperature adaptation of ICE-L. In addition, low temperature also influences on the other primary inorganic ions transfer and the cell maintains activity by keeping ratio balance among different ions. Above all, it is necessary for Antarctic ice microalgae to survive and breed by maintaining the stability of K^ ＋ content and the balance of Na^ ＋/Cl^ -.  相似文献   

Comparative application of two mathematical models to predict sedimentation in Yermasoyia Reservoir,Cyprus     

V. Hrissanthou 《水文研究》2006,20(18):3939-3952

The Yermasoyia Reservoir is located northeast of the town of Limassol, Cyprus. The storage capacity of the reservoir is 13·6 × 10⁶ m³. The basin area of the Yermasoyia River, which feeds the reservoir, totals 122·5 km². This study aims to estimate the mean annual deposition amount in the reservoir, which originates from the corresponding basin. For the estimate of the mean annual sediment inflow into the reservoir, two mathematical models are used alternatively. Each model consists of three submodels: a rainfall‐runoff submodel, a soil erosion submodel and a sediment transport submodel for streams. In the first model, the potential evapotranspiration is estimated for the rainfall‐runoff submodel, and the soil erosion submodel of Schmidt and the sediment transport submodel of Yang are used. In the second model, the actual evapotranspiration is estimated for the rainfall‐runoff submodel, and the soil erosion submodel of Poesen and the sediment transport submodel of Van Rijn are used. The deposition amount in the reservoir is estimated by means of the diagram of Brune, which delivers the trap efficiency of the reservoir. Daily rainfall data from three rainfall stations, and daily values of air temperature, relative air humidity and sunlight hours from a meteorological station for four years (1986–89) were available. The computed annual runoff volumes and mean annual soil erosion rate are compared with the respective measurement data. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Assessing the impact of the hydraulic properties of a crusted soil on overland flow modelling at the field scale     

Nane Chahinian  Marc Voltz  Roger Moussa  Gwenn Trotoux 《水文研究》2006,20(8):1701-1722

Soil surface crusts are widely reported to favour Hortonian runoff, but are not explicitly represented in most rainfall‐runoff models. The aim of this paper is to assess the impact of soil surface crusts on infiltration and runoff modelling at two spatial scales, i.e. the local scale and the plot scale. At the local scale, two separate single ring infiltration experiments are undertaken. The first is performed on the undisturbed soil, whereas the second is done after removal of the soil surface crust. The HYDRUS 2D two‐dimensional vertical infiltration model is then used in an inverse modelling approach, first to estimate the soil hydraulic properties of the crust and the subsoil, and then the effective hydraulic properties of the soil represented as a single uniform layer. The results show that the crust hydraulic conductivity is 10 times lower than that of the subsoil, thus illustrating the limiting role the crust has on infiltration. Moving up to the plot scale, a rainfall‐runoff model coupling the Richards equation to a transfer function is used to simulate Hortonian overland flow hydrographs. The previously calculated hydraulic properties are used, and a comparison is undertaken between a single‐layer and a double‐layer representation of the crusted soil. The results of the rainfall‐runoff model show that the soil hydraulic properties calculated at the local scale give acceptable results when used to model runoff at the plot scale directly, without any numerical calibration. Also, at the plot scale, no clear improvement of the results can be seen when using a double‐layer representation of the soil in comparison with a single homogeneous layer. This is due to the hydrological characteristics of Hortonian runoff, which is triggered by a rainfall intensity exceeding the saturated hydraulic conductivity of the soil surface. Consequently, the rainfall‐runoff model is more sensitive to rainfall than to the subsoil's hydrodynamic properties. Therefore, the use of a double‐layer soil model to represent runoff on a crusted soil does not seem necessary, as the increase of precision in the soil discretization is not justified by a better performance of the model. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

固态热释法测定土壤中的痕量汞     

孟素玲  陈令娟 《山东国土资源》2006,(Z1)

根据汞的热不稳定性,采用热释法测定土壤中的汞,以NaOH和Na2O2为化学吸附剂,直接取样进行测定。方法快速、简便,检出限≤4.0ng/g。经国家一级标准物质分析验证,结果与标准值相符,20次测定的RSD均小于3%。  相似文献   

Numerical Simulation Study on the Impacts of Tropospheric O3 and CO2 Concentration Changes on Winter Wheat.Part I: Model Description          下载免费PDF全文

ZHENG Changling  WANG Chunyi 《Acta Meteorologica Sinica》2006,20(1):109-116

Ozone is well documented as the air pollutant most damaging to agricultural crops and other plants.It is reported that tropospheric O3 concentration increases rapidly in recent 20 years. Evaluating and predicting impacts of ozone concentration changes on crops are drawing great attention in the scientific community. In China, main study method about this filed is controlled experiments, for example, Open Top Chambers. But numerical simulation study about impacts of ozone on crops with crop model was developed slowly, what is more, the study about combined impacts of ozone and carbon dioxide has not been reported.The improved agroecosystem model is presented to evaluate simultaneously impacts of tropospheric O3 and CO2 concentration changes on crops in the paper by integrating algorithms about impacts of ozone on photosynthesis with an existing agroecosystem biogeochemical model (named as DNDC). The main physiological processes of crop growth (phenology, leaf area index, photosynthesis, respiration, assimilated allocation and so on) in the former DNDC are kept. The algorithms about impacts of ozone on photosynthesis and winter wheat leaf are added in the modified DNDC model in order to reveal impacts of ozone and carbon dioxide on growth, development, and yield formation of winter wheat by coupling the simulation about impacts of carbon dioxide on photosynthesis of winter wheat which exists in the former DNDC. In the paper, firstly assimilate allocation algorithms and some genetic parameters (such as daily thermal time of every development stage) were modified in order that DNDC can be applicable in North China. Secondly impacts of ozone on crops were simulated with two different methods-one was impacts of ozone on light use efficiency , and the other was direct effects of ozone on leaves photosynthesis. The latter simulated results are closer to experiment measurements through comparing their simulating results. At last the method of direct impacts of ozone on leaf growth is adopted and the coe cients about impacts of ozone on leaf growth and death are ascertained. Effects of climate changes, increasing ozone, and carbon dioxide concentration on agroecosystem are tried to be simulated numerically in the study which is considered to be advanced and credible.  相似文献   

Spatial analysis of the impact of land-use on surface runoff and soil erosion-a case study of western Jilin     

Juana P Moiwo 《东北亚地学研究》2006,9(1):80-93

IntroductionNever before hasit beensotrue than now,thatlandis ali mitedresource.Population growth and as-sociated human activities,especially agricultureacross the world have not only led to land degrada-tion,but soil loss at rates that have pushed arablesoils to frontier thresholds.In the absence of arablesoil,the human environment would cease to groworeven demise(Ramet al.,2006).Studies haveshownthat in many regions of the world,runoff andsoil erosion differ withland-use type.Judson(1965)re…  相似文献   

土层随机地震反应的动力可靠度计算     

门玉明  黄义 《地球科学与环境学报》2002,24(1):43-45

研究了土层的随机地震反应分析方法 ,建立了基岩输入地震动加速度功率谱函数为白噪声和过滤白噪声时土层的动力可靠度计算理论  相似文献   

Variations in dissolved CO2 and CH4 in a first‐order stream and catchment: an investigation of soil–stream linkages     

Diane Hope  Sheila M. Palmer  Michael F. Billett  Julian J. C. Dawson 《水文研究》2004,18(17):3255-3275

Spatial and seasonal variations in CO₂ and CH₄ concentrations in streamwater and adjacent soils were studied at three sites on Brocky Burn, a headwater stream draining a peatland catchment in upland Britain. Concentrations of both gases in the soil atmosphere were significantly higher in peat and riparian soils than in mineral soils. Peat and riparian soil CO₂ concentrations varied seasonally, showing a positive correlation with air and soil temperature. Streamwater CO₂ concentrations at the upper sampling site, which mostly drained deep peats, varied from 2·8 to 9·8 mg l^?1 (2·5 to 11·9 times atmospheric saturation) and decreased markedly downstream. Temperature‐related seasonal variations in peat and riparian soil CO₂ were reflected in the stream at the upper site, where 77% of biweekly variation was explained by an autoregressive model based on: (i) a negative log‐linear relationship with stream flow; (ii) a positive linear relationship with soil CO₂ concentrations in the shallow riparian wells; and (iii) a negative linear relationship with soil CO₂ concentrations in the shallow peat wells, with a significant 2‐week lag term. These relationships changed markedly downstream, with an apparent decrease in the soil–stream linkage and a switch to a positive relationship between stream flow and stream CO₂. Streamwater CH₄ concentrations also declined sharply downstream, but were much lower (<0·01 to 0·12 mg l^?1) than those of CO₂ and showed no seasonal variation, nor any relationship with soil atmospheric CH₄ concentrations. However, stream CH₄ was significantly correlated with stream flow at the upper site, which explained 57% of biweekly variations in dissolved concentrations. We conclude that stream CO₂ can be a useful integrative measure of whole catchment respiration, but only at sites where the soil–stream linkage is strong. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

The birth of the Paratethys during the Early Oligocene: From Tethys to an ancient Black Sea analogue?     

H.-M. Schulz  A. Bechtel  R.F. Sachsenhofer   《Global and Planetary Change》2005,49(3-4):163-176

Deeper water black shales, overlain by coccolith-bearing marlstones representing the incipient Paratethys (example: Early Oligocene; Austrian Molasse Basin), have sedimentary characteristics similar to those of the Holocene Black Sea since 7500 years bp. Framboid pyrite size, biomarker and C–N-isotope data additionally indicate that isolation of the Paratethys resulted in Black Sea-type characteristics during nannoplankton zone NP 23.In contrast to the estuarine circulation across the Bosphorus since 7500 years bp, marine conditions prevailed in the incipient Paratethys during NP 21/22. Nitrogen was fixed and low organic carbon accumulation rates prevailed. In both settings a vertical density water-column stratification was accompanied by photic zone anoxia, and by anaerobic methane oxidation in the Paratethys. In the Paratethys increased run off, starting in NP 22, led to estuarine circulation during NP 23. During this period cyclic blooms of calcareous nannoplankton resulted in high calcite accumulation rates which diluted the coeval clay sedimentation. Similar sedimentary features in the Black Sea and the Paratethys during the earliest Oligocene are result from opposite paleoceanographic developments, both leading to estuarine circulation patterns. In the Black Sea, permanent photic zone anoxic conditions were established 7500 years bp in response to the first invasion of saline Mediterranean waters into the former freshwater lake. In contrast, brackish surface water in the Paratethys resulted from nutrient-rich freshwater diluting the marine water body.  相似文献