Impact of land use, land cover and morphometry on stream hydrochemistry and fine sediment geochemistry along the transect of Alaknanda basin, Garhwal Himalaya, India: an integrated study

Hydrochemistry and bed sediment geochemistry are two key components for understanding the dynamics of earth's processes. The present study examines the impact of land use/land cover and morphometric characteristics of the watersheds on streams water hydrochemistry and geochemistry of fine fraction of bed sediment. To achieve our objectives, we collected and analyzed 21 stream water and bed sediment samples. We found that the geochemistry of the fine fraction and stream hydrochemistry did not exhibit a strong relationship, likely because of non-equilibrium with fast-moving stream water. Glacier cover in watersheds influences the total dissolved solids (TDS), chloride, and nitrate in stream water. Dark minerals in bed sediment influence K+ and Mg+2 ions and the bed sediment characteristics exert control over the K+ concentration in streams water. The concentration of dissolved silica in stream water exhibits a high dependency on elevation, gradient, circulatory ratio, and form factor. The geochemistry of bed sediments reveals that fine sediments have undergone little or no chemical weathering and, hence, have a low Chemical Index of Alteration (CIA). The lack of a relationship between the geochemistry of fine sediments and bed sediment mineralogy highlights the complex origin of fine sediments other than bed sediment weathering. The morphometric parameters of the watersheds reasonably control the Na2O, K2O, and Al2O3 concentrations in the fine fraction of bed sediments. Agricultural activity influences the Fe2O3 and P2O5 concentrations in fine sediments. Barren land and forest exhibited positive and negative relationships, respectively, with mobile oxides in the fine sediment.