Last reviewed 1 Oct 2026 · 7 min read
Farm ponds
A farm pond is a small water body built on a farm to collect and store runoff (or pump water) for supplementary and life-saving irrigation, livestock and domestic use, fish culture, groundwater recharge and fire fighting. They are widely promoted in rain-fed regions under state programmes and schemes (check the current scheme and subsidy details).
Types
| Type | Description | Suitable site |
|---|---|---|
| Excavated (dugout) pond | Pit excavated in the ground; spoil banked around | Flat or gently sloping land (below about 4 %), deeper soils, where runoff or a pumped supply reaches |
| Embankment (surface) pond | Earth dam across a depression or a gully; storage upstream | Sloping ground with a natural depression |
| Excavated + embankment (combined) | Dugout with an embankment on the lower side | Moderate slopes (about 4–8 %) |
| Spring-fed, dugout in groundwater | Fed by seepage | Where the water table is high |
| Lined pond | Plastic-lined pond for high-seepage soils or drip supply | Anywhere with a catchment |
Site selection
- Adequate catchment with a runoff yield (not too large — avoid heavy silt).
- Soil with enough clay and low seepage (pervious sand or gravel is unsuitable unless lined); a deep, uniform soil layer for excavation.
- Topography: a natural depression or the lowest corner, close to the area to be irrigated (so water can be applied by gravity or short pumping), and away from trees (roots, shade and leaf litter), buildings and flood-prone paths.
- A stable spillway site (non-erodible).
- Land ownership and cost.
Capacity design
Required storage water demand during the use period + seepage loss + evaporation loss + silt allowance (about 10–20 % of capacity or as estimated):
Evaporation loss (pan evaporation × pan coefficient 0.7–0.8) × average water-spread area; seepage depends on the soil and lining.
A pond must supply 600 m³ for irrigation. Evaporation losses are estimated at 12 % and seepage at 15 % of the use, and the silt allowance is 10 % of the total capacity.
- Use evaporation seepage m³.
- With silt allowance: — about 850 m³.
Volume of an excavated pond
For a pond with rectangular top and bottom and constant side slopes, the prismoidal formula gives the volume exactly:
where is the depth, and is the area at mid-depth. Bottom dimensions top dimensions for a side slope horizontal : 1 vertical.
The top of a pond is 20 m × 15 m, depth m, side slope .
- Bottom: m and m, so m².
- Mid-depth dimensions: m and m, so m². m².
- .
(A common check — the frustum formula gives the same result for the same shape. The excavation volume is also the earthwork that can build the embankment.)
Components of a pond
- Catchment and inlet channel (with a silt trap or settling basin).
- Excavated basin (with the stable side slope about 1:1 to 2:1 depending on soil — flatter in sandy soil).
- Embankment (for embankment ponds) — see below.
- Spillway (emergency overflow) — grassed/earthen or pipe, capacity to pass the design flood with freeboard.
- Outlet (pipe/siphon or pump) for withdrawal.
- Fencing, vegetation, safety steps, trash rack.
Seepage and evaporation control
| Measure | Notes |
|---|---|
| Compacted clay lining (about 30 cm) | Cheap where clay is available; requires protection from cracking |
| Bentonite (soil mixing) | Swells to seal sandy soils (about 5–10 % by mass) |
| Plastic film/geomembrane (LDPE, silpaulin ~250–300 gsm, HDPE) | Very effective; covered with soil to protect from UV and animals |
| Cement, masonry or concrete lining | Expensive; for small tanks |
| Soil sealing (sodium carbonate, chemical dispersants), asphalt | Less common |
| Evaporation reduction | Depth (reduces area-to-volume ratio), windbreaks, floating covers, monolayers, shade nets |
Typical pond depth is 3–4 m (as it reduces evaporation per unit volume).