Inter-Basin Water Transfer: Hydrologic Water Balance and Link Canal Hydraulics

 Inter-basin water transfer diverts surface runoff from donor basins with surplus water to recipient basins experiencing deficit. Evaluating basin yield viability requires establishing a long-term hydrologic water balance equation: $P - E - R - \Delta S = 0$ ​Where $P$ is precipitation, $E$ is evapotranspiration, $R$ is surface/subsurface runoff, and $\Delta S$ is storage change. Surpluses are determined based on $75\%$ dependable annual yield $(Y_{75}),$ calculated from flow duration curves. Link canal hydraulic design incorporates head loss equations for long-distance open channels and lift stations: $$h_f = \frac{f \cdot L \cdot v^2}{2 \cdot g \cdot D}$$ ​Where $f$ is Darcy friction factor, $L$ is link conduit length, $v$ is flow velocity, and $D$ is equivalent hydraulic diameter. ​Managing spatial water availability mismatch across India—where the Ganga-Brahmaputra basins hold significant surface runoff while southern peninsular rivers face acute seasonal deficits—drives the Na...
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Design of Lined Canals: Hydraulic Optimization and Seepage Control

 Lining irrigation canals reduces seepage losses, prevents waterlogging, protects against weed growth, and permits higher non-scouring velocities. For maximum hydraulic efficiency, a lined canal section must yield maximum discharge $(Q)$ for a given cross-sectional area $(A)$ by minimizing wetted perimeter $(P).$

​For a rigid trapezoidal lined canal with side slope $m$ (horizontal) to 1 (vertical), the most hydraulically efficient section satisfies:

$$R = \frac{y}{2}$$

​Where $R$ is the hydraulic mean radius $(R = \frac{A}{P})$ and $y$ is depth of flow. When side slopes are set at $60^\circ (m = 1/\sqrt{3}),$ the section becomes a semi-hexagon. Discharge is computed using Manning’s equation:

$$Q = \frac{1}{n} \cdot A \cdot R^{2/3} \cdot S^{1/2}$$

​Where $n$ is Manning’s roughness coefficient and $S$ is longitudinal bed slope.

​Legacy concrete-lined canals in major command areas like the Indira Gandhi Nahar Pariyojana (IGNP) suffer from joint degradation, structural cracking, and high maintenance costs under harsh temperature cycles.

​Modern canal modernization under the Pradhan Mantri Krishi Sinchayee Yojana (PMKSY) deploys multi-layered geotextile composite linings—combining High-Density Polyethylene (HDPE) geomembranes with fiber-reinforced concrete (FRC) overlays. Mechanized slip-form pavers ensure continuous, joint-free placement, reducing seepage losses by up to $95\%$ while increasing permissible flow velocities up to $2.5\text{ m/s}.$

​Note: This technical content was curated and structured with AI assistance to support technical education.

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