{"title":"Chemical Weathering Rates, C-Q Relationships, Fluxes, Dam Impact and pCO2 Potential in the Ganga Headwaters: Insights From Weekly Time-Series Data","authors":"Shaifullah, Indra S. Sen","doi":"10.1029/2024GB008320","DOIUrl":null,"url":null,"abstract":"<p>Predicted alterations to the hydrological cycle due to higher temperatures at the end of this century will impact riverine processes such as weathering, erosion, and sediment transport. The Himalayan River basins, with their steep slopes, heavy rainfall, and increasing river engineering projects, are excellent sentinels for monitoring climate change and human impacts on rivers. However, few attempts have been made to capture the river mountainous catchment interaction over shorter time scales (weeks to months) to capture pulses of enhanced chemical weathering rates and other riverine processes. Here, we present a weekly time-series record of dissolved inorganic constituents near the mouth of the Alaknanda and Bhagirathi rivers—the two headwater rivers of the Ganga River—with a weekly resolution during 2018–2019. We report new estimates of discharge-weighted concentrations and fluxes. We found chemical weathering rates of 98.2 ± 54.0 and 32.2 ± 20.4 t/km<sup>2</sup>/year and CO<sub>2</sub> consumption yields by silicate weathering of 3.7 ± 1.5 × 10<sup>5</sup> and 1.8 ± 1.2 × 10<sup>5</sup> mol CO<sub>2</sub>/km<sup>2</sup>/year for the Alaknanda and Bhagirathi basins, respectively, which are significantly higher compared to the global chemical weathering rate and CO<sub>2</sub> consumption yield of ∼24 t/km<sup>2</sup>/year and ∼1 × 10<sup>5</sup> mol CO<sub>2</sub>/km<sup>2</sup>/year, respectively. We find that the concentration-discharge relationship shows both chemostatic and dilution trends, with the Tehri dam strongly influencing the hydrology of the Bhagirathi River. The alkalinity-DIC framework reveals that the Himalayan weathering acts as a net source of atmospheric pCO<sub>2</sub> over a timescale of 10<sup>5</sup>–10<sup>7</sup> years. Further, we show that a sampling campaign spreaded well throughout the year is imperative in reducing uncertainties in flux estimation.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 3","pages":""},"PeriodicalIF":5.4000,"publicationDate":"2025-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Global Biogeochemical Cycles","FirstCategoryId":"89","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1029/2024GB008320","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENVIRONMENTAL SCIENCES","Score":null,"Total":0}
引用次数: 0
Abstract
Predicted alterations to the hydrological cycle due to higher temperatures at the end of this century will impact riverine processes such as weathering, erosion, and sediment transport. The Himalayan River basins, with their steep slopes, heavy rainfall, and increasing river engineering projects, are excellent sentinels for monitoring climate change and human impacts on rivers. However, few attempts have been made to capture the river mountainous catchment interaction over shorter time scales (weeks to months) to capture pulses of enhanced chemical weathering rates and other riverine processes. Here, we present a weekly time-series record of dissolved inorganic constituents near the mouth of the Alaknanda and Bhagirathi rivers—the two headwater rivers of the Ganga River—with a weekly resolution during 2018–2019. We report new estimates of discharge-weighted concentrations and fluxes. We found chemical weathering rates of 98.2 ± 54.0 and 32.2 ± 20.4 t/km2/year and CO2 consumption yields by silicate weathering of 3.7 ± 1.5 × 105 and 1.8 ± 1.2 × 105 mol CO2/km2/year for the Alaknanda and Bhagirathi basins, respectively, which are significantly higher compared to the global chemical weathering rate and CO2 consumption yield of ∼24 t/km2/year and ∼1 × 105 mol CO2/km2/year, respectively. We find that the concentration-discharge relationship shows both chemostatic and dilution trends, with the Tehri dam strongly influencing the hydrology of the Bhagirathi River. The alkalinity-DIC framework reveals that the Himalayan weathering acts as a net source of atmospheric pCO2 over a timescale of 105–107 years. Further, we show that a sampling campaign spreaded well throughout the year is imperative in reducing uncertainties in flux estimation.
期刊介绍:
Global Biogeochemical Cycles (GBC) features research on regional to global biogeochemical interactions, as well as more local studies that demonstrate fundamental implications for biogeochemical processing at regional or global scales. Published papers draw on a wide array of methods and knowledge and extend in time from the deep geologic past to recent historical and potential future interactions. This broad scope includes studies that elucidate human activities as interactive components of biogeochemical cycles and physical Earth Systems including climate. Authors are required to make their work accessible to a broad interdisciplinary range of scientists.