Rivers, chemical weathering and Earth's climate

We detail the results of recent studies describing and quantifying the large-scale chemical weathering of the main types of continental silicate rocks: granites and basalts. These studies aim at establishing chemical weathering laws for these two lithologies, describing the dependence of chemical weathering on environmental parameters, such as climate and mechanical erosion. As shown within this contribution, such mathematical laws are of primary importance for numerical models calculating the evolution of the partial pressure of atmospheric CO₂ and the Earth climate at geological timescales. The major results can be summarized as follow: (1) weathering of continental basaltic lithologies accounts for about 30% of the total consumption of atmospheric CO₂ through weathering of continental silicate rocks. This is related to their high weatherability (about eight times greater than the granite weatherability); (2) a simple weathering law has been established for basaltic lithologies, giving the consumption of atmospheric CO₂ as a function of regional continental runoff, and mean annual regional temperature; (3) no such simple weathering law can be proposed for granitic lithologies, since the effect of temperature can only be identified for regions displaying high continental runoff; (4) a general law relating mechanical erosion and chemical weathering has been validated on small and large catchments. The consequences of these major advances on the climatic evolution of the Earth are discussed. Particularly, the impacts of the onset of the Deccan trapps and the Himalayan orogeny on the global carbon cycle are reinvestigated. To cite this article: B. Dupré et al., C. R. Geoscience 335 (2003).     

黄河流域夏季分区面雨量预报研究

介绍黄河流域分区夏季面雨量预报的研究成果，精心挑选51个具有较好代表性的测站对黄河流域夏季降水的时空演变特征进行分析，使用K均值动态聚类对黄河流域的夏季降水进行了客观分区，并计算出各流域夏季面雨量。通过对黄河流域夏季雨量与500hPa环流，海温、OLR、中纬阻高，高原积雪，欧亚积雪等重要影响因子的关系分析，结合黄河流域夏季面雨量年降和年代际演变特征的分析，研究出黄河流域分区夏季面雨量预测的基本方法和模型，并通过客观化的数学方法建立黄河流域夏季面雨量预测系统，预测系统十年回报的结果显示出具有较的预测技巧。     

2002年7～8月海河流域面雨量预报的误差分析

对天津市气象台和河北省气象台在2002年7—8月的海河流域面雨量24h、48h预报进行了误差对比分析，列举了几种预报误差，并利用模糊数学中的综合评判法，计算了它们的模糊评分。结果表明：海河流域的面雨量预报有一定的可信度，把其作为水文模式的初值，有较高的利用价值；对于各气象台各自辖区内的预报，范围越小，预报越准确；在对面雨量预报效果的评估上，80％(或80)这一数值是客观、可信的。     

三峡工程大江截流的水文技术

鉴于三峡工程大江截流水深大，流量大，工期紧，特别是截流过程中要考虑不断航因素，因此，在大江截流和二期围堰阶段的施工进程中，应充分考虑到各方面的因素，尽可能采取一切减少大江截流和二期围堰施工难度的手段和措施，其中水文测验，水文气象预报，河道观测，水文分析与计算和水力学计算等水文工作则是为顺利实施高质量大江截流的重要条件。     

STUDIES ON TERRACES AND RIVER SYSTEM CHANGES OF THE UPPER YELLOW RIVER

Ｉ.ＴｈｅＴｅｒｒａｃｅｓｏｆｔｈｅＵｐｐｅｒＹｅｌｌｏｗＲｉｖｅｒＴｈｅｔｅｒｒａｃｅｓｏｆｔｈｅｕｐｐｅｒＹｅｌｌｏｗＲｉｖｅｒａｒｅｍｏｓｔｌｙｄｉｓｐｅｒｓｅｄａｌｏｎｇｔｈｅｗｉｄｅｒｃｏｕｒｓｅｓｉｎｓｅｖｅｒａｌＭｅｓｏｚｏｉｃＣｅｎｏｚｏｉｃｂａｓｉｎｓ(Ｆｉｇｕｒｅ1).1.ＴｅｒｒａｃｅｓｂｅｔｗｅｅｎＮｇｏｒｉｎｇＬａｋｅａｎｄＧｙａｒｉｎｇＬａｋｅＴｈｅｓｕｒｆａｃｅｌａｙｅｒｓｏｆｔｈｅｓｅｄｉｍｅｎｔｉｎｔｈｅｗｉｄｅａｎｄｓｈａｌｌｏｗｂａｓｉｎｓｗｈｅｒｅｔｈｅＹｅｌｌ…     

天山北坡降水对河流水沙情势影响

以天山北坡头屯河流域为例，在对山区不同海拔的降水特征、侵蚀产沙情势以及河流水沙运移特点分析的基础上，详尽就山区降水对河流水沙情势的年际变化、年内变化以及月变化的影响进行了分析研究，并就降水对不同海拔的河流水沙情势的影响强度及相互关系作了探讨．     

内陆待开发地区产业发展模式探讨——以内蒙古为例

以内蒙古为例，探讨了内陆待开发地区的产业发展模式，内陆待开发地区经济发展的主要制约因素是缺乏资金，缺乏技术，缺乏人才，因此，其经济发展必须有选择，有重点地优先发展部分行业。一般说来，待开发的内陆地区其经济发展必须以资源优势为依托，以市场为导向，开发优质名牌产品，发展优势产业，建设主导产业，带动地区经济的起飞。     

Effects of geology and human activity on the dynamics of salt-water intrusion in three coastal aquifers in southern Spain

 Mathematical modelling of salt-water intrusion processes in three aquifers on the southern coast of Spain (Río Verde, Río Vélez and Castell de Ferro) reveals that, although all three systems are subject to the same climate and seasonal over-exploitation, geological and human factors have very different effects on the dynamics of contamination. In the Río Verde aquifer, the most important influence is the high volume of extractions occurring during the dry season; in Río Vélez, the intrusion is strongly controlled by infiltration of water from the river to the aquifer, and, in the Castell de Ferro system, an intensely karstified carbonate massif lying in contact with both the sea water and the detrital aquifer represents the main entrance point for influx of sea water and subsequent washing of the aquifer. We have undertaken a mathematical simulation of various possible measures to counteract intrusion, according to the specific characteristics of the process in each aquifer. These measures include artificial recharge, use of natural recharge from the river as a hydraulic barrier, and the construction of a low-permeability barrier. Received: 5 December 1995 · Accepted: 12 April 1996     

Methodical approach to distribution of epilithic and drifting algae communities in a French subalpine river: Inferences on water quality assessment

In a sub-alpine river, the Asse, with an unpredictable discharge regime, chlorophyll, density and taxonomic diversity of both drifting and periphytic communities were studied from a methodical approach. The investigations based on stamping two close cross-sections to know their spatial distributions in a heterogeneous bed substrate showed a heterogeneous pattern of colonization mainly influenced by hydrological variables as the current velocity, the size of the substrata (gravel-pebble-boulder). For the drifting algae, mainly composed with benthic species temporarily unhooked to the substrata, the heterogeneity of the distribution was reduced in fast flow which induced a mixing of the whole mass of water. For the periphyton, some results indicated that the greatest diversity and the highest chlorophyll concentration were found on pebble substratum where the current velocity was moderate. These results have also shown that the classical methods used to day for investigations were inadequate for most Mediterranean rivers. It was really difficult to estimate the water quality from classical index created for use in regular large plain rivers.