Irrigation Methods in Nepal Compared: Surface, Drip, Sprinkler, Tubewell, Solar

Nepal cultivates roughly 2.6 million hectares of farmland, of which about 2.26 million hectares are classed as irrigable according to the Department of Water Resources and Irrigation (DWRI, 2019). Irrigation infrastructure of some kind now reaches roughly half of the cultivated area, yet much of it works only during and shortly after the monsoon: many canals draw on rivers that shrink sharply in winter and spring, so only a fraction of the equipped area is estimated to receive reliable year-round irrigation. Closing that gap is the central goal of the Irrigation Master Plan 2019 (Updated 2024), the government's guiding document for the sector.

Because Nepal spans the flat Tarai plains, the mid-hills and the high mountains, no single irrigation method fits everywhere. Gravity-fed canals dominate the Tarai and river valleys, centuries-old farmer-built kulo channels water hill terraces, tubewells tap the Tarai's rich groundwater, and pressurised micro-irrigation (drip and sprinkler) plus solar pumping are spreading fast where water is scarce or electricity and diesel are costly. The six approaches compared on this page differ enormously in water-use efficiency, cost and crop suitability.

Surface irrigation - flooding basins, borders or furrows with water conveyed by gravity canals - remains by far the most common irrigation method in Nepal, especially for paddy in the Tarai and in river valleys. Modern canal building began in the 1920s with the Chandra Canal (Chandra Nahar) in Saptari district, and the sector grew through large state projects after the 1950s. The largest is the Sunsari-Morang Irrigation Project in eastern Tarai, with a command area of about 68,000 hectares fed by a 53-kilometre main canal; it was built between 1964 and 1973 under an agreement with India and handed to Nepal in 1975. DWRI's 2019 inventory recorded about 2,254 surface irrigation systems in operation covering roughly 728,000 hectares under public management or joint management.

The appeal of canal irrigation is its low running cost: once built, gravity does the work, no fuel or electricity is needed, and it suits water-loving crops such as rice. Its weakness is water loss. The Food and Agriculture Organization (FAO) gives an indicative field application efficiency of about 60 percent for surface irrigation, and unlined earthen canals lose a further 10-20 percent or more in conveyance, so overall scheme efficiency often falls to around 50 percent or below. In Nepal the losses are compounded by monsoon-dependent rivers, silt-laden intakes, ageing structures and tail-end farmers receiving far less water than those near the canal head.

Farmer-managed irrigation systems are canal networks that communities themselves designed, built and continue to operate - digging channels (kulo), maintaining intakes and allocating water through their own rules, often for generations. Researchers estimate Nepal has on the order of 15,000 to 20,000 FMIS, the great majority in the hills, and they are credited with serving roughly 70 percent of the country's total irrigated area. Famous examples include the historic raj kulo (royal canals) of the hill towns and the Chhattis Mauja system on the Tinau River in Rupandehi, which farmers have run collectively for generations.

FMIS are internationally studied as a model of common-property water governance: water users' associations set contribution rules, mobilise labour for repairs and resolve disputes locally, which keeps costs low and accountability high. Their limitations are technical rather than institutional - temporary brushwood intakes can wash away in floods, earthen channels leak, and many systems supply only supplementary monsoon-season water. Government and donor programmes therefore focus on jointly upgrading headworks and lining canals while leaving management with the farmers, a policy direction reinforced by the Water Resources Act 2049 (1992) and the Irrigation Master Plan.

The Tarai plains sit on productive aquifers, making pumped groundwater the second pillar of Nepali irrigation. Shallow tubewells - typically bored to about 50 metres or less and fitted with small pumps - are cheap enough for individual smallholders, while deep tubewells reach lower aquifers and can serve whole farmer groups but cost far more to drill and operate. Government records compiled around 2011 counted 87,117 shallow tubewells and 863 deep tubewell systems installed in the Tarai, and CGIAR researchers estimate groundwater now supports production on roughly half a million hectares, almost entirely through shallow tubewells. The Groundwater Resources Development Board (GWRDB) maps aquifers and supports tubewell development.

Tubewells give farmers what canals often cannot: on-demand water in the dry season, enabling spring rice, wheat and vegetables. Their main constraint is energy. Most shallow tubewells still run on diesel pumps, whose fuel cost squeezes margins and discourages full use, while many deep tubewells built decades ago fell idle because of high electricity costs and weak group management. This energy problem is precisely what solar pumping (below) and grid electrification are now trying to solve, including pilot projects to solarise old deep tubewells in the Tarai.

Drip irrigation delivers water slowly and directly to each plant's root zone through pipes and emitters. It is the most water-efficient method available: FAO's indicative field application efficiency is about 90 percent, against about 75 percent for sprinkler and 60 percent for surface methods, and conveyance losses are near zero because water moves in closed pipes. In Nepal, drip suits widely spaced, high-value crops - tomatoes, cauliflower and other vegetables, strawberries, citrus and banana orchards - and works well on hill terraces, where a tank placed a few metres above the field provides enough gravity pressure without any pump. Low-cost drip kits promoted by the NGO iDE (International Development Enterprises) and partners have reached well over a hundred thousand Nepali smallholder plots, mainly for off-season vegetables in the mid-hills. The trade-offs are upfront cost, the need for filtered water to prevent emitter clogging, and regular maintenance.

Sprinkler irrigation sprays water over the field like artificial rain from rotating nozzles. At roughly 75 percent application efficiency it saves substantially over flooding, and unlike surface irrigation it needs no field levelling, so it fits uneven or sloping land and light soils that drain too fast for basins. In Nepal it is used for closely spaced crops such as wheat, pulses, potatoes, tea, coffee and vegetable nurseries, and hill farmers can again exploit natural elevation to create pressure by gravity. Its drawbacks are wind drift and evaporation losses on hot, windy days, unsuitability for water-loving paddy, and higher equipment costs than open channels. As a rule of thumb for 'drip vs sprinkler' decisions: drip wins for row and orchard crops and where every litre counts; sprinkler wins for dense field crops, nurseries and rough terrain.

Solar irrigation pumps (SIPs) use photovoltaic panels to run electric pumps that lift water from tubewells, rivers or ponds. The Alternative Energy Promotion Centre (AEPC) began systematically promoting SIPs in 2016 under the Renewable Energy Subsidy Policy 2016, officially covering 60 percent of the system cost, with many local governments topping up the subsidy further. According to the International Water Management Institute (IWMI), which studied the sector in its report 'Solar Irrigation in Nepal - A Situation Analysis' and through the SoLAR (Solar Irrigation for Agricultural Resilience) project, more than 3,000 SIPs had been installed by 2023, concentrated in the Tarai districts of Koshi and Madhesh provinces. Demand far outstrips supply: AEPC received around 13,000 applications in fiscal year 2019/20 alone.

The attraction is obvious. Once installed, a solar pump has essentially zero fuel cost, freeing Tarai farmers from diesel price shocks and enabling cheap dry-season pumping; it also cuts emissions and can be paired with drip or sprinkler systems for very high overall efficiency. The caveats are the high upfront cost without subsidy, reduced output in cloudy monsoon months (when it is least needed), and a longer-term policy concern flagged by IWMI: because solar water is nearly free to pump, unregulated expansion could over-extract groundwater, so metering, grid-connection schemes that let farmers sell surplus power to the Nepal Electricity Authority, and aquifer monitoring are being piloted.

The right method depends on three questions: what water source is available, what crop is being grown, and what the farmer can invest. The comparison below combines FAO's indicative efficiency figures with typical Nepali use cases; actual performance varies with design and management.

In practice, methods are increasingly combined. A Tarai farmer may use a solar pump on a shallow tubewell to feed sprinklers for wheat; a hill vegetable grower may fill a plastic pond from a spring and run gravity drip lines; a canal-fed village may line its kulo and add storage to stretch winter flows. The Irrigation Master Plan explicitly encourages such conjunctive use of surface water, groundwater and renewable energy.

Nepal's sector roadmap is the Irrigation Master Plan 2019, whose updated edition was approved at ministerial level on 30 May 2024 (17 Jestha 2081 BS). The plan aims to extend irrigation to essentially all irrigable land - including about 1.5 million hectares in the Tarai and over half a million hectares identified in the hills and mountains - and to raise national cropping intensity to about 230 percent by 2045 through reliable year-round water supply. Key strategies include modernising and lining existing canals, expanding groundwater use where aquifers allow, inter-basin transfer projects such as Bheri-Babai and Sunkoshi-Marin that divert water to Tarai commands, and mainstreaming micro-irrigation and solar pumping.

For students and farmers comparing irrigation methods, the direction of travel is clear: Nepal is moving from extensive, low-efficiency flood irrigation towards a mixed portfolio in which canals are rehabilitated, groundwater is energised by solar power, and drip and sprinkler systems capture more crop per drop on high-value land. Which method 'wins' depends on the farm - but on efficiency alone, the ranking is consistent worldwide and in Nepal: drip first, sprinkler second, surface flooding last.