Assessment of irrigation water quality for groundwater in Semi-Arid Region, Bangalore, Karnataka

Abstract

Anthropogenic activities-related degradation of groundwater quality has emerged as a major concern. The variation in geomorphological, geological, and hydrogeological factors are assessed for the thirty groundwater samples, collected from Bangalore North, Bangalore Rural district, Karnataka, during the pre-monsoon season. The study’s goal is to evaluate major ion chemistry and several physicochemical parameters viz. salinity hazard (EC), sodium adsorption ratio (SAR), residual sodium carbonate (RSC), chloride hazard (CH), total hardness (TH), magnesium hazard (MH), permeability index (PI), percent sodium (%Na), kelly’s ratio/index (KR/KI), soluble sodium percent (SSP), chloro-alkaline index (CAI), and ion balance. The Principal Component Analysis (PCA) in performed to evaluate the Irrigation Water Quality Index (IWQI) considering and water quality parameters like EC, Na+ (sodium), HCO3− (bicarbonates), Cl− (chlorides), SAR content of groundwater. To determine the overall water quality suitable for irrigation use, the irrigation water quality index ratings were computed. Along with this, Gibbs diagrams and Wilcox plots were created based on analytical results, and groundwater quality. The Gibbs diagram reveals that more than 83% of samples were evaporation dominates and regulate the mechanism for the chemistry of groundwater except few samples (R7, R8, T7, T8, U3) which accounts for nearly 17% , and have high sodium content. Whereas the Wilcox plot represents, most of the samples are within the permissible limits for irrigation use. Ten percent of the transition sample (T6) and almost 60% of the rural samples (R1, R2, R4, R5, R6, R10) had no irrigation restrictions. Low irrigation restriction was present in 20% of urban samples (U4, U7), 80% of transition samples (T1, T2, T4, T5, T7, T8, T9, T10), and 30% of rural samples (R3, R7, R9). Moderate restrictions on irrigation use were present in 10% of rural samples (R8), 10% of transition sample (T3), and 80% of urban samples (U1, U2, U3, U5, U6, U8, U9, U10). The natural resources of water bodies have been impacted by unplanned economic and industrial activities that have sped up urbanization, industrialization, infrastructural development, and population growth. Most of the rural samples had no toxicity risk for most of the crops, while transition samples had limited restriction and proper monitoring & judicious application for irrigation will be better for most of the crops except salt-sensitive crops. More than 80% of urban samples had moderate restriction only plants with moderate tolerance to salts may be grown.

Keywords

• Gibbs diagram
• kelly’s ratio
• Wilcox plot
• permeability index
• ion balance