Investigation of groundwater consumption to cope with the inadequate piped water supply in continuous and intermittent supply systems: A case study in Bangalore, India

[EN] Although the supply of piped water to the Indian cities is increasing, the demand is not always fulfilled. This gap in water demand and supply is usually bridged by using alternate sources of water, mostly groundwater. Bangalore, the capital city of Karnataka, is one of the fastest developing metropolitan cities in India is also facing piped water supply issues. The groundwater is the main source of alternate water supply in the city. In the present study, a District Metered Area (DMA) is selected in the Bangalore South-West division; this DMA has both intermittent and continuous water supply systems. The water distribution network (WDN) of study DMA contains four inlets and three supply zones. The first is a continuous water supply system whereas the second and third are the intermittent systems. The impact of inequitable supply in the study DMA is evaluated and the consumption of groundwater to cope with insufficient water supply is analyzed. The Lorenz Curve and Gini Coefficient are used to assess the inequity in groundwater extraction under intermittent and continuous supply zones. The data from the field flowmeters, consumer meter reading, and door-to-door questionnaire survey are used for the analysis. The questionnaire survey includes RR number, presence of wells/borewells, horsepower (HP) of the pumps used, building type, the number of inhabitants, and the floors in each building. In the continuous supply system, a questionnaire survey was untaken for 80% of the connections, whereas in the intermittent supply system random sampling was used. The questionnaire survey analysis showed that 53% of the consumers in the continuous supply system rely on piped water supply, whereas others used groundwater as well as piped water supply. The study illustrated the gap in groundwater consumption between supply zones within intermittent water supply systems as well as between intermittent and continuous water supply zones. Reliability on groundwater was high even in continuous supply systems indicating insufficient pressures resulting in unsatisfied demands. The study indicated that just increasing the access to the piped water supply to the consumers is not sufficient, the acceptable quality with adequate pressure of water should be delivered to reduce the use of groundwater. The inferences from the study can be used to regulate groundwater extraction.Priyanka, B.; Bharanidharan, B.; Sheetal Kumar, K.; Mohan Kumar, M.; Srinivas, V.; Nibgoor, SR.; Kishore, Y. (2024). Investigation of groundwater consumption to cope with the inadequate piped water supply in continuous and intermittent supply systems: A case study in Bangalore, India. Editorial Universitat Politècnica de València. https://doi.org/10.4995/WDSA-CCWI2022.2022.1482

Three-Dimensional Modelling of Heterogeneous Coastal Aquifer: Upscaling from Local Scale

The aquifer heterogeneity is often simplified while conceptualizing numerical model due to lack of field data. Conducting field measurements to estimate all the parameters at the aquifer scale may not be feasible. Therefore, it is essential to determine the most significant parameters which require field characterization. For this purpose, the sensitivity analysis is performed on aquifer parameters, viz., anisotropic hydraulic conductivity, effective porosity and longitudinal dispersivity. The results of the sensitivity index and root mean square deviation indicated, that the longitudinal dispersivity and anisotropic hydraulic conductivity are the sensitive aquifer parameters to evaluate seawater intrusion in the study area. The sensitive parameters are further characterized at discrete points or at local scale by using regression analysis. The longitudinal dispersivity is estimated at discrete well points based on Xu and Eckstein regression formula. The anisotropic hydraulic conductivity is estimated based on established regression relationship between hydraulic conductivity and electrical resistivity with R2 of 0.924. The estimated hydraulic conductivity in x and y-direction are upscaled by considering the heterogeneous medium as statistically homogeneous at each layer. The upscaled model output is compared with the transversely isotropic model output. The bias error and root mean square error indicated that the upscaled model performed better than the transversely isotropic model. Thus, this investigation demonstrates the necessity of considering spatial heterogeneous parameters for effective modelling of the seawater intrusion in a layered coastal aquifer

Estimating anisotropic heterogeneous hydraulic conductivity and dispersivity in a layered coastal aquifer of Dakshina Kannada District, Karnataka

•Constraining the 3D variable density numerical model with field measurements.•Estimation of anisotropic heterogeneous hydraulic conductivity.•A novel method to validate solute concentration results with ERT profile.•Verification of assigned aquifer topography and estimated geological formation. The solution for the inverse problem of seawater intrusion at an aquifer scale has not been studied as extensively as forward modeling, because of the conceptual and computational difficulties involved. A three-dimensional variable-density conceptual phreatic model is developed by constraining with real-field data such as layering, aquifer bottom topography and appropriate initial conditions. The initial aquifer parameters are layered heterogeneous and spatially homogeneous that are based on discrete field measurements. The developed conceptual model shows poor correlation with observed state variables (hydraulic head and solute concentration), signifying the importance of spatial heterogeneity in hydraulic conductivity and dispersivity of all the layers. The conceptual model is inverted to estimate the anisotropic spatially varying hydraulic conductivity and the longitudinal dispersivity at the pilot points by minimizing the least square error of state variables across the observation wells. The inverse calibrated model is validated for the hydraulic head at validation wells and the solute concentration is validated with equivalent solute concentration derived from the electrical resistivity, which shows good results against the field measurements. The verification of estimated anisotropic hydraulic conductivity with the electrical resistivity tomography image shows good agreement. This investigation gives an insight about constraining the highly parameterized inverse model with real-field data to estimate spatially varying aquifer parameters for an effective simulation of the seawater intrusion in a layered coastal aquifer