Page 91 - AJWEP-22-5

Evaluation of riverbank water suitability

scalability dimensions are assigned a score of 1, propagation of infiltrated river water and thus has an
whereas those with significant limitations in these indirect impact on both river water quality (K6) and
aspects are scored as 0. These indicators ensure the groundwater quality (K7) by mediating transport
overall feasibility and long-term sustainability of and mixing processes.
the water source site. (iv) Aquifer thickness (K4): The thickness of the
unconfined aquifer defines the available cross-
3.1.2. Quantitative indicators sectional area for subsurface flow and controls
In this study, the quantitative evaluation system the static storage capacity of the system. A thicker
comprises eight indicators that reflect key hydrological, aquifer facilitates greater recharge volumes under
geological, and environmental factors influencing the a given hydraulic gradient and increases buffering
suitability of riverside groundwater source development. capacity during periods of high demand or drought.
These indicators are not entirely independent in While largely independent in formulation, K4
practice, as they exhibit varying degrees of internal interacts with K3 in determining total transmissivity
correlation and mutual influence. Understanding such and modulates the influence of groundwater depth
interrelationships is crucial for enhancing the accuracy (K8) on pumping feasibility and long-term aquifer
and robustness of the overall evaluation framework. drawdown behavior.
The following are the quantitative indicators (v) Presence of continuous impermeable layers (K5):
employed in this study: Impermeable or semi-permeable interlayers
(i) Minimum river discharge during the dry season significantly affect vertical recharge and may
(K1): Low-flow river discharge directly constrains compartmentalize the aquifer, reducing connectivity
the potential for induced recharge and the between the river and extraction zones. This spatial
sustainable yield of riverside sources. During dry heterogeneity complicates conceptual models and
periods, river flow is predominantly maintained may result in over- or underestimation of induced
by baseflow contributions from regional aquifers, recharge. K5 is closely related to K2 and K3, as
creating a bidirectional interaction between surface riverbed clogging and vertical flow resistance both
and subsurface systems. Moreover, insufficient contribute to reduced effective permeability. It
discharge may reduce the hydraulic gradient also has a potential masking effect on the apparent
necessary for lateral infiltration, thereby indirectly relationship between K6 (river water quality) and
influencing aquifer hydraulic conductivity (K3) and K7 (groundwater quality), by acting as a selective
riverbed permeability (K2). barrier or hydraulic filter.
(ii) Riverbed permeability (K2): Sediment deposition (vi) River water quality (K6): As riverside water sources
on the riverbed alters the permeability and rely substantially on induced infiltration, river water
transmissivity of the hyporheic zone, serving as a quality is a critical determinant of overall source
critical control on the efficiency of river–aquifer suitability. However, its impact does not operate
interactions. Excessive siltation can form semi- in isolation. Infiltrated river water undergoes
permeable or impermeable layers, thereby limiting natural attenuation processes within the vadose and
infiltration. Notably, this indicator is correlated with saturated zones, where its quality is modified by
K3, as fine particles may migrate into upper aquifer aquifer-specific physical and chemical properties.
layers, leading to clogging and a reduction in effective Therefore, the interaction between K6 and K7 must
porosity and overall hydraulic performance. Hence, be carefully interpreted: high-quality river water
K2 and K3 should be considered in conjunction may improve local groundwater conditions, while
when assessing recharge potential. low-quality surface water may result in cumulative
(iii) Aquifer hydraulic conductivity (K3): Hydraulic contamination, especially in shallow or highly
conductivity determines the capacity of the aquifer permeable aquifers.
to transmit water both horizontally and vertically. (vii) Groundwater quality (K7): Groundwater quality
In anisotropic or compositionally heterogeneous reflects both the native geochemical background
media, conductivity may vary by direction and and anthropogenic influences, as well as the
depth. Together with K2, the presence of silt layers cumulative effects of river-induced recharge. Its
or interbeds can alter the vertical-to-horizontal interpretation should therefore consider upstream
conductivity ratio, affecting induced recharge indicators, particularly K6 and K3. In certain
dynamics. Furthermore, K3 influences the spatial settings, elevated pollutant concentrations in

Volume 22 Issue 5 (2025) 85 doi: 10.36922/AJWEP025260208