Vegetation influences on water yields from grassland and shrubland ecosystems in the Chihuahuan Desert

This study examines runoff generated under simulated rainfall on Summerford bajada in the Jornada Basin, New Mexico, USA. Forty‐five simulation experiments were conducted on 1 m² and 2 m² runoff plots on grassland, degraded grassland, shrub and intershrub environments located in grassland and shrubland communities. Average hydrographs generated for each environment show that runoff originates earlier on the vegetated plots than on the unvegetated plots. This early generation of runoff is attributed to soil infiltration rates being overwhelmed by the rapid concentration of water at the base of plants by stemflow. Hydrographs from the degraded grassland and intershrub plots rise continuously throughout the 30 min simulation events indicating that these plots do not achieve equilibrium runoff. This continuously rising form is attributed to the progressive development of raindrop‐induced surface seals. Most grassland and shrub plots level out after the initial early rise indicating equilibrium runoff is achieved. Some shrub plots, however, display a decline in discharge after the early rise. The delayed infiltration of water into macropores beneath shrubs with vegetation in their understories is proposed to explain this declining form. Water yields predicted at the community level indicate that the shrubland sheds 150 per cent more water for a given storm event than the grassland. Copyright © 2002 John Wiley & Sons, Ltd.     

Stable isotope values of Costa Rican surface waters

Stable isotope data of surface waters from the humid tropics in general, and Costa Rica in particular, are scarce. To improve our understanding of the spatial distribution of stable isotopes in surface waters, we measured δ¹⁸O and δD in river and lake (n=63) and precipitation (n=3) samples from Costa Rica. We also present data from the IAEA/WMO isotopes in precipitation network as context for our study. Surface water isotope values do not strongly correlate with elevation, stream head elevation, stream length, distance from Caribbean Sea, or estimated mean annual precipitation for the country as a whole. However, the data show distinct regional trends. The δ¹⁸O and δD values downwind of mountain ranges are inversely related to the altitude of the ranges the air masses traverse. In the lee of the high Talamanca Range, δ¹⁸O values are 6–8‰ lower, while in the lee of the lower Tilarán Range δ¹⁸O values are 2–3‰ lower than upwind sites along the Caribbean Slope. An altitude effect of −1.4‰ δ¹⁸O/km is present on the Pacific slope of southern Costa Rica, equivalent to a temperature effect of −0.3‰/°C. The Nicoya and Osa Peninsulas have higher values than upwind sites, suggesting input of Pacific-sourced moisture, evaporative enrichment, or decreased condensation temperatures. Elevated and increasing d-excess values inland along the Nicaragua Trough suggest a recycled component may be an important contributor to the water budget. These data provide preliminary stable isotope information for Costa Rica, and will benefit paleoclimatic research in the region. More detailed studies would be beneficial to our understanding of the controls on stable isotope composition of tropical waters.     

Water availability for the greening of Kuwait

Water resources for agricultural development and landscape enhancement in Kuwait are very scarce; the quality is saline (brackish), and the soil texture is sandy, incapable of holding nutrients and moisture. Most of the rainfall in Kuwait either evaporates due to the high temperatures or percolates through the soil. The rainfall is not sufficient to recharge the underground water supply. A variety of alternative water sources have been studied, including seawater desalination and wastewater treatment. Wastewater treatment proved to be convenient due to the relatively low salinity detected in the treated water. Furthermore, the amount of wastewater is expected to increase as more residential areas are connected to the sewage system as the population increases.

The development of a greenery plan for Kuwait requires intensive water management. This goal can be achieved through manpower training in landscape development, selection of plants tolerant to arid environments, usage of appropriate irrigation and drainage systems, promotion of greenery programs within public and the governmental agencies for their direct participation in urban area beautification, and extension of wastewater treatment techniques.     

地下水潮汐现象的物理机制和统一数学方程

用新的分层承压含水层模式 ,不但考虑含水层的力学压缩性质 ,而且考虑含水层的渗流特性 ,并结合扰动信息源的频率特性 ,分别研究扰动源地球固体潮、大气潮和地表负荷潮对承压井水位和流量的影响机理 ,给出相应的偏微分方程。从方程的解释或数值解讨论扰动源与承压井含水层的力学压缩参数、渗流特性参数及与频率特性频数的关系 ,进而给出承压井水位和流量对地球固体潮、大气潮和地表负荷潮汐响应的统一数学方程及其潮汐响应函数 ,并揭示了上述几类潮汐扰动信息源对承压井水位和流量影响的物理机理     

水对断层摩擦滑动稳定性的影响

在不同含水条件下研究了光面、含脆性物质夹层和含延性物质夹层 3类断层的摩擦滑动行为 ,认为水对断层滑动稳定性和摩擦滑动的速度依赖性有重要影响。建立了含有岩性、围压 (深度 )和含水量 3因素的断层活动稳定性的模式 ,认为脆性断层更多地表现为速度弱化 ,少量水的存在易于出现黏滑 ,高孔隙压时会表现为稳滑 ;半脆性或半延性的断层在少量水或较低孔隙压的情况下会表现出速度弱化 ,也就可能出现黏滑 ,但孔隙压较高后 ,会表现出速度强化 ,滑动也就会是稳定的 ;延性断层多为速度强化 ,不出现黏滑。提出水的进入降低了系统的稳定性 ,水的存在增加了系统的稳定性。这是考虑水或一般流体对岩体或断层活动稳定性影响时需要考虑的两个方面     

A discussion on the records of water level ‘precursors’ in Well Shuozhou, Shanxi Province

A lot of slow fluctuations of water level have been observed in the original recording maps of subsurface fluid in Well Shuozhou, Shanxi Province. Some typical recording maps of the “precursors” are introduced in the paper and the features of the “precursors” recorded by the well are analyzed. The results show that 38% strong earthquakes possess this kind of record, which has a fluctuation period arranging from several to tens of minutes and appear mostly two days before the earthquakes. Moreover, the mechanism, transmission and responding conditions of well water level are discussed, as well as the scientific meaning and practical value of the “precursor” of the well water level in earthquake predictions. Foundation item: State Natural Science Foundation of China (19973011).     

Do the Austrian blackfly fauna (Diptera: Simuliidae) support the typological approach of the EU water framework directive?

The Austrian blackfly fauna were analysed with regard to spatial (ecoregions, bioregions), vertical (altitude classes) and longitudinal zonation characteristics [stream order, biocoenotic (= fish) regions] on the basis of 2600 investigation sites. Of a total of 45 species recorded, Simulium ornatum, S. variegatum, S. argyreatum and S. reptans are the most common and most frequently distributed species, occurring in 60% of the investigated sites. Although the Austrian blackfly fauna seem to be quite well documented (on average one investigation site per 32 km²) the jackknife analyses indicates that there are still some fauna deficits. Whereas the species diversity of the main ecoregions is quite similar, the number of species differs clearly between the bioregions. Within the typological context of the Water Framework Directive, the Austrian Simuliidae confirm the bioregions as the most useful spatial units for river typology. A further optimisation in predicting a target list of blackfly species of a site can be achieved by subdividing the bioregions into either catchment area and altitude classes or into longitudinal zonation types (biocoenotic regions).     

野外简易脱气装置简介

根据水力学原理结合水氡在实验室分析中水样鼓泡脱气的方法 ,进行了大量的野外试验 ,研制开发了野外简易脱气装置。通过几个月的试观测 ,脱气装置气流稳定 ,脱气效率高 ,完全可以满足自动化观测仪器对气量的需求。该装置解决了地下水化学在野外冷水泉无法进行气体观测的难题 ,而且制作简单、费用低廉 ,非常便于推广。     

DETECTION OF MULTILAYER CIRRUS CLOUD USING FY-1C DATA

There are ten channels in the FY-1C polar-orbiting meteorological satellite of China.Thesechannels cover visible,near-infrared and infrared spectral bands.Based on simulating analysis ofsingle layer and multilayer clouds that cirrus clouds possibly overlap low water clouds,the casestudy using FY-1C data is performed.Results show that FY-1C data can be used to analyzemultilayer clouds,especially for the ease of low water cloud overlaid by cirrus.