How an Irrigation Project Delivers Sustainable Outcomes amid Climate Change

Making irrigation systems more climate-resilient increased season-to-season water supply and more than doubled the cultivated area and productivity of upland farms. Photo credit: ADB.

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Climate-smart remodeling and operation of irrigation systems help improve water availability and upland farm productivity in two provinces of Cambodia.


Until recently, the farms of Kampong Thom and Battambang provinces mirrored the sorry state of irrigated agriculture in Cambodia.  Not enough water was reaching these farms, leaving an overwhelming portion uncultivated, particularly during the dry season.

The Uplands Irrigation and Water Resources Management Sector Project has started to reverse this situation.  By remodeling and modernizing three irrigation systems and making them more climate-resilient, the project has increased season-to-season water supply and more than doubled the cultivated area and productivity of upland farms.  Through on-time completion and government and community co-management of the rehabilitated systems, it has also provided farmers with immediate and sustained socio-economic benefits.

To achieve target outcomes, the Asian Development Bank-supported project introduced irrigation scheduling based on the actual crop-water requirements in Cambodia. It also put in place a unique tripartite agreement between private growers, the Ministry of Water Resources and Meteorology (MOWRAM), and farmer water user communities that made private growers provide annual fees for the operation and maintenance of the main canal they were using to irrigate their farms. This would be a model for the application of the users-pay principle for irrigation water use by the private sector and could pave the way for commercial agriculture in the country.

Project Snapshot

  • 20 September 2015 : Date Approved
  • 30 September 2021 : Date Completed

  • SDR43.121 million (~$60 million) : Financing

  • Financing :
  • Executing agency :
    • Ministry of Water Resources and Meteorology (MOWRAM)
  • Implementing agency :
    • Department of Farmer Water User Communities (DFWUC)

Despite becoming nationally self-sufficient in rice and a net exporter of the commodity, nearly one-fourth of Cambodia’s provinces were experiencing food deficits, and 16.1% of its population was undernourished, as of project preparation in 2014.  Underlying this phenomenon is the difficulty of sustaining year-round production because of the highly variable and seasonal rainfall and river flows. Climate change, now heightening this variability and battering the country with more severe weather extremes including long dry spells and more intense floods, is expected to exacerbate the agricultural constraints and vulnerability of farmers’ livelihoods and the rural economy. Without remodeling and climate adaptation, the existing irrigation systems will be unable to cope and assist the country in addressing these mounting challenges.


According to the latest data, Cambodia has a total of 2,730 irrigation systems, with a command area aggregating about a third of its total 3.98 million hectares (ha) of agricultural land.  However, most of these systems were either dysfunctional or underperforming because of aging infrastructure, lack of resources for rehabilitation, and inadequate operation and maintenance (O&M).  They were increasingly incapable of meeting the irrigation requirements of their command areas, impacting both the amount and productivity of the lands that could be tilled as well as the crops that could be grown.

As a case in point, the two core irrigation systems improved by this project have a total command area of 20,301 ha.  But of this, only 11,935 ha was being cultivated before the project—1,015 ha in the dry season and 10,920 ha in the wet season. 

In response, the government has prioritized irrigation under phases 3 and 4 of its Rectangular Strategy on Growth, Employment, Equity, and Efficiency.  ADB, in partnership with other development agencies, has extensively supported this priority through standalone and sector projects, including some that incorporated policy development.  


Solutions provided by the project focused on (i) enhancing the efficiency and climate resilience of irrigation systems, (ii) improving water and crop productivity, and (iii) improving water resource management through stakeholder capacity building.  These solutions drew on accomplishments and lessons from completed and ongoing initiatives in agriculture, water, and related sectors in Cambodia and other countries. Those that are directly associated with this project are the Water Resources Management Sector Development Program, Climate-Resilient Rice Commercialization Sector Development Program, and Greater Mekong Subregion Flood and Drought Risk Management and Mitigation Project.

Climate-resilient infrastructure and technologies. Undersluices, spillways, and headworks were rehabilitated. Pumping systems and drainage and flood protection facilities were improved.  Canal flow measurement and control systems were installed.  These infrastructural improvements enhanced the climate resiliency and conveyance and distribution capacity of the irrigation systems and were supported by the establishment of hydrometeorological stations in the watersheds, laser land leveling of the project farms, and the grassing of the main canal banks made mandatory in the works contracts.

Climate-smart operations. Modern canal operation techniques were disseminated by (i) introducing irrigation scheduling to make the irrigation water supplies demand-driven (ii) installing water gauges in the three canal systems to support demand-driven supplies, and (iii) installing hydrological and meteorological (hydromet) stations in the watersheds and on rivers for real-time data collection to support informed decision making for integrated water management, particularly during droughts.  Joint reservoir operations were designed to support equitable water distribution and improve water-sharing arrangements during droughts.

Government and community co-management of facilities and O&M cost-sharing. Farmer water user communities were formed and involved in the design and implementation of the subprojects.  They have subsequently taken charge and met the costs of O&M of the distribution canals, while MOWRAM has remained responsible for the main canals. 

Stakeholder capacity building.  Technical and project and water resource management training provided to the water user communities and government project agencies improved knowledge and skills, enabling them to better operate and manage the irrigation systems and achieve the intended project results mostly beyond targets.  The communities were also trained in organizational development and management, and this helped them to grow strong organizations and community leaders.

Users-pay innovation with the private sector. Under the agreement, private commercial growers benefitting from one of the main canals rehabilitated by the project will be paying annual fees to support O&M of the main canal.  The agreement was made between the farmer water user communities, MOWRAM, and the private growers.


Except for one, the project achieved or overachieved its targets.  Project success was also marked by on-time completion, which is uncommon in foreign-funded projects in Cambodia and most other ADB developing member countries.  Project completion could have been 9 months ahead of schedule had it not been for the breaching of a dam in Battambang province by flash floods in October 2020.   The damage on the dam, previously not included in the project scope but immediately repaired with the use of loan proceeds, did not affect the attainment of the project results as shown in the summary below.

Results Chain

Targets and Indicators with Baselines




Enhanced water and agriculture productivity in the project areas

By 2022:

Average annual crop production increased to 4.25 tons per ha

(2015 baseline: 1.65 tons/ha)


  • 4.42 tons per ha (July 2021 estimate)


  1. Efficiency and climate resilience of irrigation systems enhanced

By 2021:

1a. Dry and wet season cultivated area increased to 29,500 ha. (2015 baseline: 13,500 ha)


  • 31,140 ha


1b. Irrigation efficiency of three irrigation systems increased by 100%. (2015 baseline: 20%)

  • More than 300%


1c. Drainage facilities for 1,800 ha improved. (2015 baseline: 0 ha)

  • 1,780 ha


1d. 200 haa of land leveled by laser leveling. (2015 baseline: 0 ha)

  • 200.6 ha


1e. 21,000 ha land improved through irrigation, drainage, and/or flood protection.

  • 21,026 ha


1f. 25% of unskilled laborers in civil works are women.

  • 26.2%  


  1. Water resources management improved

By 2021:

2a. Three FWUCs formed and trained (2015 baseline: 0)


  • Three FWUCs formed and trained


2b. 30% of FWUC members are women (2015 baseline: 0)

  •  48% women


2c. 30% of FWUC management committee members are women (2015 baseline: 0)

  •  36% women


2d. Annual O&M plan prepared during design of each irrigation system.

  • Yes


2e. O&M funds allocated by the government for main canals and reservoirs.

  • 2021 and 2022 O&M budget proposals submitted to the Ministry of Economy and Finance


2f. Eight hydromet stations installed in the watersheds (2015 baseline:0)

  • 30 stations installed
aAdjusted during the midterm review from 2,000 ha at appraisal in view of the finding that most farmlands were already leveled and did not need laser leveling.

FWUC = farmer water user community, O&M = operation and maintenance


Building on an earlier case study, which identified several factors for this project’s success, the following key lessons emerge:

Enhancing the climate resilience of irrigation systems requires the audit and calibration of all associated structures.  While highlighting the growing unpredictability of flash floods under climate change, the unanticipated breaching of the Bassac dam was also instructive of the need to assess and ensure the sturdiness of all structures linked to the irrigation systems being rehabilitated.  This need should be addressed in all future ADB-financed irrigation rehabilitation projects.   

Adjustments in engineering designs should be explored to avoid safeguards issues that can compromise project performance.   Because this project expressly prohibited activities that would require resettlement, the engineering designs of irrigation channels were modified at a few locations.  This allowed the project to proceed without safeguard compliance issues, which could have caused delays or reductions in the project scope.

Project impacts are maximized by synergizing existing initiatives.  The project tapped the gains from and resources of other ADB-financed sector initiatives to maximize results.  It capitalized on the government sub-decree of March 2015, mandating farmers’ participation in the O&M of irrigation systems, to form farmer water use communities. This sub-decree came about with support from the Water Resources Management Sector Development Program.  It collaborated with the Climate-Resilient Rice Commercialization Sector Development Program to increase farmers’ access to improved seed supplies, land leveling, and agriculture value chain facilities being established in the project area.  It also collaborated with the Greater Mekong Subregion Flood and Drought Risk Management and Mitigation Project for the installation of hydromet stations. The synergy was beneficial for all the projects and created impacts far greater than they would have individually achieved.

Strong government commitment and community participation play a pivotal role in the success of projects. The project management office was fully staffed, and the project was included in the government budget even before loan approval. Consultant recruitment and procurement of works for the core subprojects were completed before loan effectiveness.  The resulting high degree of project readiness enabled timely startup and provided the impetus for efficient and effective implementation, which was also highlighted by prompt government responses to implementation issues and challenges.  Along with vigorous community participation reinforced by the government mandate on farmer water user communities, strong ownership and commitment by the government to the project played a pivotal role in its success. 

In addition to the above, the earlier case study also cited the importance of smart contract packaging and quality contract management, a smart implementation arrangement, a well-thought-out design and monitoring framework, early establishment of performance monitoring systems, and clear project administration guidelines in the successful implementation of ADB-financed projects.

Piseth Long
Senior Project Officer, Cambodia Resident Mission, Asian Development Bank

Piseth Long has been primarily responsible for managing projects in the agriculture and water management sector of Cambodia since he joined ADB in July 2008.  He has also worked in the Lao People’s Democratic Republic, Myanmar, and the Philippines. Before joining ADB, he was a senior program officer at DANIDA.  He holds a master’s degree in Economics from the School of Oriental and African Studies, University of London, and a bachelor’s degree in Economics from the Institute of Economics, Cambodia.

Raza M. Farrukh
Project Administration Unit Head, Azerbaijan Resident Mission, Asian Development Bank

Raza Farrukh is primarily responsible for supervising and managing the ADB portfolio in Azerbaijan.  He has been with ADB for 19 years, working in the Philippines, Indonesia, Pakistan, Cambodia, the Lao People’s Democratic Republic, Viet Nam, and Tajikistan.  He has a Master of Engineering degree in Water Resources Engineering from the Asian Institute of Technology, Thailand, and a bachelor’s degree in Civil Engineering from the University of Engineering and Technology, Pakistan.

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