🛠️ Soil and Water Conservation Structures

Soil and water conservation structures are planned interventions that reduce runoff losses, control erosion, and improve groundwater recharge in rainfed watersheds.

---

Soil and Water Conservation: Principles

Soil erosion and runoff are the two primary threats to dryland agricultural productivity. Soil and water conservation (SWC) structures are engineered interventions designed to:

1. Slow down runoff — reduce velocity and volume of surface water flow
2. Trap eroding soil — prevent on-site and off-site soil loss
3. Recharge groundwater — allow rainfall to percolate rather than drain away
4. Provide supplemental water — store runoff for critical irrigation

SWC structures are classified as mechanical (earthen or masonry structures) and vegetative (biological/agronomic measures). Both are used in combination for effective watershed treatment.

---

Earthen and Masonry Bunds

Contour Bunds

• Earthen embankments constructed along contour lines (lines of equal elevation)
• Height: 15–30 cm; base width: 2–3 m
• Intercept surface runoff before it gains erosive velocity
• Spacing depends on slope steepness: closer spacing on steeper slopes
• Suitable slope range: 1–6%
• Common in: Rajasthan, Madhya Pradesh, Maharashtra
• Low-cost; farmer-constructed with MGNREGS support

Graded Bunds

• Similar to contour bunds but built with a slight gradient (0.2–0.4%) to allow controlled drainage
• Prevents waterlogging behind the bund — critical in semi-arid black soil areas
• Appropriate where soils have slow infiltration rates
• Common in: Telangana, Andhra Pradesh

Field Bunds

• Boundary embankments around individual fields
• Traditional practice across India — integral to paddy cultivation
• Retain monsoon rainwater in terraced rice paddies
• Also reduce inter-field runoff and soil mixing

Stone Bunds

• Rock or stone embankments aligned on contour
• Built in areas with abundant local stone: Rajasthan, Karnataka, Deccan Plateau
• Advantages: highly durable; no maintenance required once constructed; permeable (allows some water to pass)
• Cost-effective where stone is locally available
• Often allow establishment of grasses and shrubs on bund top for additional stabilization

---

Check Dams

Check dams are structures constructed across stream channels to impound runoff, trap sediment, and recharge groundwater.

Purpose

• Slow and store runoff in stream beds
• Raise the water table in adjacent wells (lateral recharge)
• Reduce peak discharge during storms
• Provide water for supplemental irrigation

Types of Check Dams

Type	Material	Best Use	Key Feature
Earthen	Compacted soil	Low-runoff areas	Low cost; spillway essential
Masonry	Cement + stone	Permanent structures	Durable; high storage
Gabion	Wire mesh + stone	Flash flood areas	Flexible; self-repairing
Rock-fill	Loose stone/boulders	Temporary/quick	Minimal construction skill

• Gabion check dams are particularly effective in flash-flood-prone dryland areas — the flexible wire mesh absorbs hydraulic energy without structural failure
• Spillway design is critical for all check dams — must safely handle maximum flood discharge to prevent dam breach

Notable Programmes

• Gujarat: Sujalam Suflam water conservation programme — thousands of check dams revived groundwater in Saurashtra
• Maharashtra: Jalyukt Shivar Abhiyan — 25,000+ villages; check dams and nala deepening
• MP: Watershed Development Programme (PMKSY-WDC)

---

Percolation Tanks

• Small ponds in stream channels designed for percolation rather than storage
• Constructed at hydrogeologically favorable locations (permeable strata, fracture zones)
• Water is intentionally allowed to percolate into the aquifer — groundwater recharge purpose
• Raises dry-season well water levels in command area
• Used extensively in Karnataka, Maharashtra, Tamil Nadu

Farm Ponds

Farm ponds are on-farm surface storage structures that capture field runoff for supplemental irrigation.

Design

• Catchment area: 0.5–5 ha per pond
• Typical size: 30 m × 30 m × 3 m (depth)
• Lined ponds: polythene lining or RCC — prevent seepage losses; costlier but store water longer
• Unlined ponds: lower cost; natural soils; some percolation loss; also serves as recharge

Use

• Store 1–3 lifts of supplemental irrigation (each lift = 5–7 cm water/ha)
• Critical irrigation at flowering/grain filling stage can save crop during dry spell
• Can also be used for fish culture (integrated farming)

Funding

• MGNREGS (Mahatma Gandhi National Rural Employment Guarantee Scheme) provides labor cost for farm pond construction
• PMKSY (Pradhan Mantri Krishi Sinchai Yojana) provides material cost support

---

Gully Control Structures

Gullies are channels cut by concentrated runoff — once formed, they expand rapidly and cannot be tilled. Control is essential.

• Gully check dams: small earthen or masonry structures across the gully channel; slow flow; allow sediment deposition and revegetation
• Silt retention structures: trap eroding soil; combined with vegetative stabilization of gully walls
• Gully plugging: fill small gullies with locally available material (stones, brush) + plant stabilizing grasses

Gully reclamation is slow — requires 3–5 years of combined structural and vegetative treatment.

---

Terracing

Appropriate for slopes >6% where standard bunds are insufficient.

• Bench terraces: horizontal step-like fields cut into hillside; highest water retention; common in Northeast India, hill states
• Broad-based terraces: gentler modification; sloped terrace with drainage channel at inner edge
• Hillside ditches / trench terraces: interceptor channels across slope; drain excess runoff safely

Terracing is labor-intensive but converts otherwise uncultivable slopes into productive land.

Trench Systems

• Staggered trenches: 0.3 × 0.3 × 3 m trenches alternated across slope; intercept sheet runoff; high percolation; common in forest and agroforestry lands
• Continuous trenches: across-slope interceptor channels; drain runoff to stable outlets

Vegetative Measures

Contour Grass Strips

• Vetiver grass (Chrysopogon zizanioides / Khus): planted in rows along contour
• Deep, dense root system stabilizes soil; above-ground biomass slows runoff
• Bioengineering approach: living barrier that improves with time
• Also useful: Napier grass, Stylosanthes, Lemongrass

Cover Crops

• Protect soil surface from raindrop splash (primary cause of soil detachment)
• Reduce runoff velocity through soil surface roughness
• Leguminous cover crops add nitrogen while protecting soil

Windbreaks and Shelterbelts

• Rows of trees/shrubs perpendicular to prevailing wind direction
• Reduce wind velocity → reduce wind erosion in arid/semi-arid zones (Rajasthan, Gujarat)
• Additional benefits: microclimate improvement, wood/fruit production

---

Government Programme: PMKSY-WDC

Pradhan Mantri Krishi Sinchai Yojana — Watershed Development Component (formerly IWMP):

• Nodal ministry: Ministry of Rural Development (DOLR)
• Target: 1678+ projects; 49 million ha treatment
• Cost: Rs 12,000/ha (general areas); Rs 15,000/ha (hilly areas)
• Duration: 4–5 years per project; 1000 ha minimum batch size
• Funding: 60% Central + 40% State

Summary Cheat Sheet

Structure	Slope Range	Primary Purpose	Typical Cost	States
Contour bund	1–6%	Runoff interception; in-situ moisture	Low	Rajasthan, MP, MH
Graded bund	1–4%	Runoff drainage (black soils)	Low	Telangana, AP
Stone bund	1–8%	Runoff interception; durable	Low-medium	Rajasthan, Karnataka
Check dam (masonry)	Stream bed	Groundwater recharge; storage	Medium-high	Nationwide
Gabion check dam	Stream bed	Flash flood areas; recharge	Medium	Semi-arid zones
Farm pond	Field scale	Supplemental irrigation storage	Medium	All rainfed states
Bench terrace	>6%	Cultivable land from slopes	High	NE India, hills
Vetiver grass strips	1–10%	Bioengineering; runoff slowing	Very low	Nationwide
Percolation tank	Stream bed	Aquifer recharge	Medium	Karnataka, MH, TN

---

References

2 sources • [1] [2]

[1]

Department of Land Resources: Watershed Guidelines

Official

[2]

Indian Council of Agricultural Research (ICAR)

Official