Traditional irrigated rice terraces

Level bench terraces with risers protected by fodder grasses, used for the irrigated production of rice, potatoes and wheat

The level bench terrace is a traditional technology that makes irrigated crop production possible on steep, erosion-prone slopes. Most such terraces in Nepal were constructed by hand many generations ago; but some new land – mostly already under rainfed cultivation on forward sloping terraces – is still being converted into irrigated terraces. The initial costs for building the terraces are very high and there are high annual maintenance costs. The climate is humid subtropical, the slopes are steep (30-60%), and the soils generally have a sandy loam texture. Terraces are cropped by farmers who mostly have less than 0.5 ha of land each. Two to three annual crops are grown, with paddy rice during the monsoon followed by potatoes and/or wheat.

Terrace beds are usually 2-6m wide and are made as wide as possible to save labour without increasing the danger of slips and landslides. The terraces were originally surveyed by eye, but now a water-tube level is used to survey new terraces. Risers are 0.8-1.5m high with a small lip (20-25 cm). The slope of the riser varies from 80 to 160%, depending on the initial gradient of the hill. Stones are incorporated in the risers, if available, and grass species such as Bermuda grass (Cynodon dactylon) and Napier grass (Pennisetum purpureum) may be planted to help stabilise the terrace edges and for use as cattle fodder. The risers are compacted (with hoes) to improve ponding conditions for paddy rice. Twice a year the risers are scraped with a special tool: whilst preparing to plant paddy rice the lower parts of risers are sliced, with the upper part left protected with grasses against the monsoon rains; and at the time of planting wheat the whole riser (including the lip) is scraped and spread as green manure on the terrace.

light green: districts in 2007

WOCAT database reference: QT NEP10

Location: Sankhu Bhulbu, Manmata subwatershed, Kathmandu district

Technology area: 1 km²

SWC measure: Structural, vegetative and agronomic

Land use: Cropland

Climate: Humid subtropical Related approach: Not documented (traditional technology)

Compiled by: Ramanand Bhattarai, District Soil Conservation Office, Lalitpur, Nepal

Date: November 2003, updated August 2004

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• Traditional irrigated rice terraces