『Abstract
　A periodic sampling (85 samples) collected fortnightly along 3 annual hydrological cycles (1990-1993) in the Niger River basin, at the outlet of Bamako (Mali), allowed the calibration of an hydrochemical model based on the hydrograph separation. As a first step, 5 reservoirs are identified: Rr the rapid runoff, Rs the superficial runoff, Rh the hypodermic or differed runoff, Ns the superficial ground water, and Np the deep ground water, also called base flow. In each reservoir, the physico-chemical composition of water is supposed to be constant with time. Along the hydrograph, or total discharge curves, and during 3 hydrological cycles, the relative proportions of each of the reservoirs fluctuate continuously. The methodology, processing step by step, is first calibrated, by using concentrations of specific tracers: dissolved Na⁺, HCO3^-, and suspended sediments (TSS). Then, the proportions of Rr, Rs, Rh, Ns, and Np, contributing to the total flow measured at each instant of sampling, are calculated. As a second step, pH and the concentrations of aqueous species (K⁺, Ca²⁺, Mg²⁺, Cl^-, SO4^2-, DOC, SiO2) , are in turn calculated by regression analysis in each reservoir. Finally a test of validity of the method is presented as a very close correlation between measured and predicted fluctuating concentrations of each of the elements. From that satisfactory stage, the geochemical budget of weathering is conducted, with particular attention to SiO2 release and CO2 consumption. Parent-rock mineralogical compositions contributing to dissolved species in the total discharge as well as in the individual flow components have been reconstituted. Rates of both chemical erosion (soil profile formation by weathering), and mechanical erosion (soil profile and landscape denudation) have been evaluated. The methodology, successfully applied to the Niger basin, is proposed as a strategic tool for studying the watershed dynamics for any time and space scales. The model revealed its ability to extrapolate and predict the geochemical or the environmental behaviour of such basins, naturally submitted to large secular or annual, regular or even catastrophic climatic oscillations.』

『バマコ（マリ）の流出口で、ニジェール川盆地における3年間の水文循環（1990〜1993）に沿って2週間ごとに定期的に採取された試料（85試料）から、水文曲線の分類に基づいた水文化学モデルの検定を行うことができた。第一段階として、5つのリザーバーが確認されている：Rr　急速な流出、Rs　表面流出、Rh　表層下または別の表面流出、Ns　表面地下水、およびNp　深部地下水、これは基底流とも呼ばれる。各リザーバーにおいて、水の物理化学的組成は時間に対して一定であると推定される。水文曲線あるいは全排出曲線に沿って、3水文循環の間に、リザーバーの各々の相対的割合は連続的に変動する。方法の中身は、段階的に処理を行って、まず特定のトレーサーの濃度を用いて検定されている：溶存 Na⁺とHCO3^-および浮遊堆積物（TSS）。それから、試料採取の各場合に測定された全流量に寄与しているRr、Rs、Rh、Ns、およびNpの割合が計算されている。第二段階として、pHおよび溶存種の濃度（K⁺、Ca²⁺、Mg²⁺、Cl^-、SO4^2-、DOC、SiO2）が各リザーバーにおいて回帰分析により同様に計算されている。最後に、方法の妥当性の試験から、それぞれの元素の変動する濃度の測定値および予想値は非常に密接な関係にあることが示されている。そのような満足できる段階から、風化の化学的収支計算が、とくにSiO2 放出と CO2 消費に注目して、行われている。個々の流れの成分におけるだけでなく全排出量中の溶存種に寄与している母岩鉱物組成が復元してある。化学的浸食（風化による土壌断面形成）および機械的浸食（土壌断面および地形削剥）の両方の速度が評価してある。ニジェール盆地にうまく適用されたこの方法は、どのような時間と空間規模でも流域の動的な営みを研究するのに戦略的に役立つ手段として提案されている。このモデルは、天然の長期あるいは年間の、規則的あるいは大変動する気候変動をこうむった盆地の地球化学的あるいは環境的挙動を推定し予想することが可能であることを示した。』

1. Introduction
2. Strategy and methodology
　2.1. Previous work
　2.2. The problems
　2.3. Distinction of 5 reservoirs
　2.4. General strategy
　2.5. Clear identification of Rs, the superficial runoff
　2.6. Clear identification of Np, the deep groundwater flow
　2.7. Particular conditions for the identification of Rr, the so-called rapid runoff
　2.8. Definition of Rh, the hypodermic runoff, and Ns, the superficial groundwater flow
　2.9. Search of coherence
3. Protocol: frequency of sampling and physico-chemical analyses required
　3.1. Frequency of sampling
　3.2. Quality of physico-chemical analyses
4. Presentation of the Niger River basin
　4.1. Geographical and geological setting
　　4.1.1. Hydrological network
　　4.1.2. Parent rocks
　　4.1.3. Soils
　　4.1.4. Climate and hydrology
　4.2. Presentation of the analyses
　4.3. Characteristic features of the 5 reservoirs
　4.4. Fluctuations of concentrations of the specific tracers as a function of the discharge (Qt)
　4.5. Relationships between Na⁺ and TSS: determination of specific concentrations
　4.6. Determination of specific tracer concentrations
　4.7. Chemio-hydrographs “prograde” and “retrograde”
5. Method, results and discussions
　5.1. Method of calculation
　5.2. Chemical composition of the reservoirs
　5.3. Fluctuations of the reservoir contribution and hydrological coherence
　　5.3.1. Succession of events
　　5.3.2. Hydrological parameters of the reservoirs
　　5.3.3. Critical discussion
　5.4. Geochemical reliability of the model
　5.5. Soil profile dynamics and geochemical coherence of the model
　　5.5.1. Biological uptakes
　　5.5.2. Dynamics of the organic carbon
　　5.5.3. Dynamics of silica: overview on silicate weathering
6. Geochemical balance of weathering
　6.1. The normative parent-rock alteration
　　6.1.1. Dissolution or hydrolysis reactions
　　6.1.2. Geochemical index of weathering (Re)
　　6.1.3. The normative rock composition: protocol of calculation
　6.2. Example of calculation
　　6.2.1. Averages rock mineral compositions
　　6.2.2. Parent-rock contributions in Rt, Np and Rr
　　6.2.3. Differential leaching as a function of the hydrological regime
7. Silica released and CO2 consumed
　7.1. SiO2 released by weathering
　　7.1.1. Overall balance of chemical weathering
　　7.1.2. Seasonal variations of Re, the index of silicate weathering
　　7.1.3. Specific processes in Rs
　　7.1.4. Relationship between activity and flux of silica
　7.2. CO2 consumed by weathering
　　7.2.1. Average CO2 consumption for the overall average 1990-1993
　　7.2.2. Fluctuations of CO2 consumption through the years 1990-1993
　　7.2.3. Relationship between SiO2 released and CO2 consumed
8. Chemical and mechanical erosion
　8.1. Rates of chemical erosion (CWR)
　8.2. Rates of mechanical erosion (MER)
　8.3. Rates of soil thickening
9. Modelling through the whole century: extrapolation to wet or dry years
　9.1. Empirical relationships and distribution of Rs, Rh, Ns and Np as functions of the total discharge
　9.2. Geochemical behaviour
10. Conclusions
Acknowledgements
Appendix
References