SVS vs MVS Water Supply Schemes Explained
Single Village and Multi Village Schemes solve the same problem at very different scales. Knowing which to design, and why, shapes every downstream decision.
Two answers to the same question
Every rural water supply scheme answers one question: how do we deliver a safe, adequate quantity of water to every household, every day, for the design period? The Single Village Scheme (SVS) and the Multi Village Scheme (MVS) are two structurally different answers, chosen mainly on the basis of the quality and reliability of the source available locally.
An SVS serves one habitation or village from a source within or very close to it. An MVS draws from one dependable source, often a river, reservoir or large well field, and distributes treated water to many habitations spread across a wide area through a network of mains.
When a Single Village Scheme is the right choice
An SVS is preferred where a village has its own sustainable source of acceptable quality, typically groundwater from a bore well or infiltration well with sufficient yield through the summer. Because everything is local, the scheme is simpler, cheaper and faster to commission.
The core components are a source (bore or open well), a pump set, a rising main to an overhead service reservoir (OHSR), and a gravity distribution network to public stand posts or household connections. The design effort concentrates on correctly forecasting demand, sizing the OHSR, selecting the pump, and running the distribution hydraulics.
When a Multi Village Scheme is required
An MVS becomes necessary where local sources are inadequate, unreliable or contaminated, for example by fluoride, salinity or over-extraction. Instead of many weak local sources, one strong regional source is developed and water is carried to every habitation.
The design is far more involved. It includes an intake structure, raw-water pumping, a water treatment plant or rapid sand filter, clear-water pumping, long transmission mains, balancing and summer-storage reservoirs, habitation-wise OHSRs and the distribution networks below each. Each habitation still needs its own demand forecast and OHSR sizing, but these now sit inside a much larger headworks-to-tail-end system.
How the design components compare
In an SVS the hydraulics are short and local: one rising main and one distribution network. In an MVS you additionally design pumping mains and gravity mains that may run for kilometres, each needing a hydraulic statement with the hydraulic grade line, residual head and correct pipe class worked out node by node.
Storage also differs. An SVS usually needs only the OHSR for daily balancing. An MVS commonly needs ground-level balancing reservoirs and summer-storage tanks to ride out source variation, in addition to the habitation OHSRs.
What stays the same
Whichever scheme you design, the fundamentals are identical: forecast the design-period population, convert it to a daily water demand using the prescribed per-capita norm, size storage for the balancing requirement, and prove that every point in the network receives water at an acceptable residual pressure.
This is why a good design tool lets you move from SVS to MVS without relearning the basics. The population forecast, demand calculation and OHSR sizing logic are shared; the MVS simply adds the extra headworks and transmission sheets on top of the same foundation.
What is the main factor in choosing SVS over MVS?
The adequacy and reliability of a local source of acceptable quality. If a village has its own sustainable, safe source, an SVS is preferred; if local sources are inadequate or contaminated, an MVS drawing from one dependable regional source is designed.
Does every habitation in an MVS still need its own OHSR?
Yes. Each habitation has its own demand forecast and overhead service reservoir for daily balancing, even though the source, treatment and transmission are shared across the whole scheme.
Which scheme needs summer-storage reservoirs?
Multi Village Schemes commonly need balancing and summer-storage reservoirs to absorb variation in the regional source, whereas a Single Village Scheme usually balances within its OHSR alone.