title: Controls of DSi in streams and reservoirs along the Kaveri River, South India.
abstract: There is an increasing body of evidence showing that land use may affect the concentration and flux of dissolved silica (DSi) and amorphous, biogenic Si particles (ASi/BSi) in surface waters. Here, we present a study of riverine waters collected within the Kaveri River Basin, which has a long history of land occupation with +43% population increase in the watershed during the last 30 years associated with agricultural practices including canal irrigation from reservoirs and, more recently, bore well pumping. We report total dissolved solids (TDS) and suspended material (TSM) for 15 river stations and 5 reservoirs along the Kaveri itself and its main tributaries sampled during pre-monsoon, monsoon and post-monsoon periods in 2006 and 2007. The TDS in the Kaveri River globally increases from the upper reaches (humid to sub-humid climate) to the lower reaches (semi-arid climate), and at a given station from monsoon (M) to hot season (HS). The DSi concentrations range from 129 μmol L(-1) (M) to 390 μmol L(-1) (HS) in the main Kaveri stream and reaches up to 686 μmol L(-1) in the Shimsha River (HS). Our results indicate that DSi and the main solutes of the Kaveri River have not drastically changed since the last 30 years despite the population increase. The pollution index of Van der Weijden and Pacheco (2006) ranges from 13% to 54% but DSi does not seem to be affected by domestic wastewater. ASi is mostly composed of diatoms and phytoliths that both play roles in controlling DSi. We suggest that DSi and ASi delivered to the cultivated areas through irrigation from reservoir may have two important consequences: increasing Si bioavailability for crops and limiting Si flux to the ocean.
authors.affiliation: Aix-Marseille Université, CNRS, IRD, CEREGE UM34, 13545 Aix en Provence, France.
authors.forename: J D
authors.initials: JD
authors.lastname: Meunier
authors.affiliation: GET-OMP, UMR 5563 CNRS/Univ. P. Sabatier/IRD, 14 avenue E. Belin, F-31400 Toulouse, France; Indo-French Cell for Water Sciences, IISc-IRD Joint International Laboratory, IISc, Bangalore 560012, India.
authors.forename: J
authors.initials: J
authors.lastname: Riotte
authors.affiliation: GET-OMP, UMR 5563 CNRS/Univ. P. Sabatier/IRD, 14 avenue E. Belin, F-31400 Toulouse, France; Indo-French Cell for Water Sciences, IISc-IRD Joint International Laboratory, IISc, Bangalore 560012, India.
authors.forename: J J
authors.initials: JJ
authors.lastname: Braun
authors.affiliation: Indo-French Cell for Water Sciences, IISc-IRD Joint International Laboratory, IISc, Bangalore 560012, India; Civil Engineering Department, IISc, Bangalore 560012, India.
authors.forename: M
authors.initials: M
authors.lastname: Sekhar
authors.affiliation: Aix-Marseille Université, CNRS, IRD, CEREGE UM34, 13545 Aix en Provence, France.
authors.forename: F
authors.initials: F
authors.lastname: Chalié
authors.affiliation: Aix-Marseille Université, CNRS, IRD, CEREGE UM34, 13545 Aix en Provence, France.
authors.forename: D
authors.initials: D
authors.lastname: Barboni
authors.affiliation: Aix-Marseille Université, CNRS, IRD, CEREGE UM34, 13545 Aix en Provence, France; Dpt of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S102TN, UK.
authors.forename: L
authors.initials: L
authors.lastname: Saccone
mesh_terms: D000383:Agriculture; D004784:Environmental Monitoring; D006812:Humic Substances / Q000032:analysis*; D007194:India; D045483:Rivers / Q000737:chemistry*; D012621:Seasons; D014873:Water Pollutants / Q000032:analysis*
chemical_list: D006812:Humic Substances; D014873:Water Pollutants
keywords: Dissolved solids; Kaveri Basin; Monsoon; Reservoir; Silicon; Weathering