『Abstract
　The Narmada River in India is the largest west-flowing river into the Arabian Sea, draining through the Deccan Traps, one of the largest flood basalt provinces in the world. The fluvial geochemical characteristics and chemical weathering rates (CWR) for the mainstream and its major tributaries were determined using a composite dataset, which includes four phases of seasonal field (spot) samples (during 2003 and 2004) and a decade-long (1880-2000) fornight time series (multiannual) data. Here, we demonstrate the influence of minor lithologies (carbonates and saline-alkaline soils) on basaltic signature, as reflected in sudden increases of Ca²⁺-Mg²⁺ and Na⁺ contents at many locations along the mainstream and in tributaries. Both spot and multiannual data corrected for non-geological contributions were used to calculate the CWR. The CWR for spot samples (CEWRspot) vary between 25 and 63 ton km^-2 year^-1, showing a reasonable correspondence with the CWR estimated for multiannual data (CWRmulti) at most study locations. The weathering rates of silicate (SilWR), carbonate (CarbWR) and evaporite (Sal-AlkWR) have contributed 〜38-58, 28-45 and 8-23％, respectively to the CWRspot at different locations. The estimated SilWR (11-36 ton km^-2 year^-1) for the Narmada basin indicates that the previous studies on the North Deccan Rivers (Narmada-Tapti-Godavari) overestimated the silicate weathering rates and associated CO2 consumption rates. The average annual CO2 drawdown via silicate weathering calculated for the Narmada basin is 〜0.032×10¹² moles year^-1, suggesting that chemical weathering of the entire Deccan Trap basalts consumes approximately 2％ (〜0.24×10¹² moles) of the annual global CO2 drawdown. The present study also evaluates the influence of meteorological parameters (runoff and temperature) and physical weathering rates (PWR) in controlling the CWR at annual scale across the basin. The CWR and the SilWR show significant correlation with runoff and PWR. On the basis of observed wide temporal variations in the CWR and their close association with runoff, temperature and physical erosion, we propose that the CWR in the Narmada basin strongly depend on meteorological variability. at most locations, the total denudation rates (TDR) are dominated by physical erosion, whereas chemical weathering constitutes only a small part (＜10％). Thus, the CWR to PWR ratio for the Narmada basin can be compared with high relief small river watersheds of Taiwan and New Zealand (1-5％) and large Himalayan Rivers such as the Brahmaputra and the Ganges (8-9％).』

1. Introduction
2. Study area and sampling locations
3. Sampling and methodology
4. Results and discussion
　4.1. Major ion chemistry
　4.2. Spatial and interannual variability
　4.3. Downstream evolution and source of major ions
　4.4. Estimation of chemical weathering rates (CWR)
　　4.4.1. Silicate weathering rates (SilWE)
　　4.4.2. Carbonate weathering rates (CarbWR)
　　4.4.3. Saline-alkaline weathering rates (Sal-AlkWR)
　　4.4.4. Uncertainties in CWR, SilWR, CarbWR and Sal-AlkWR estimations
　　4.4.5. CO2 consumption rates
　4.5. Controlling parameters
　　4.5.1. Role of climatic parameters
　　　4.5.1.1. Runoff
　　　4.5.1.2. Temperature (T)
　　4.5.2. Physical weathering
　4.6. Total denudation rate and dominance of physical weathering
5. Concluding remarks
Acknowledgements
Appendix A. Supplementary data
References