Nepal has abundant solar energy potential, with an annual capacity of 50,000 terawatt-hours and an average of 300 sunny days per year. The largely untapped solar power in the country has the potential to transform its agriculture system as energy use in agriculture is very low compared to the South Asian average. However, its agricultural expansion is challenged by the country’s low per-capita land availability and fragmented nature of land distribution, which significantly impacts its costs and feasibility. Diesel continues to be a prominent energy source used in the country, especially in the Terai region. Improving access to solar energy can transform irrigation systems, ensuring a consistent water supply, which is the first prerequisite of commercial agriculture. Solar power opens avenues to enhance the agriculture value chain and deepen market penetration by establishing processing and cold storage facilities.

One of the primary challenges for solar expansion is the scarcity of suitable land for large-scale solar installations. Nepal’s rugged terrain and limited flat spaces pose significant constraints for traditional solar expansion methods. The 2021 Agriculture Census reveals that over 85 percent of farming households possess less than one hectare of land, with an average of 2.8 parcels per farmer, each averaging 0.19 hectares in size. As a result, acquiring private land for solar energy is difficult in Nepal. Additionally, allocating more land for solar power directly competes with the food and nutritional security of small-scale farmers. Meanwhile, using public land for solar panels has its own challenges due to various policy hurdles. Installing solar panels along an extensive network of irrigation canals can be a unique solution to these land constraints.

Nearly 80 percent of our total irrigated land depends on surface irrigation, with a vast network spanning over 1,000 km (command area). The Sikta Irrigation System in Nepalgunj, Banke has two main canals—Sikta East Canal and Sikta West Canal—totalling 98.7 kilometres, along with eight branch canals, each about 20 kilometres long, making a total of 160 kilometres excluding tertiary canals. Assuming an average canal width of 100 meters, the combined surface area covered by all these canals is approximately 16 square kilometres, 1,600 hectares of land within this irrigation network. This land can accommodate a solar plant with an 800 megawatts (MW) capacity, based on an estimated one MW per two hectares. Such a plant could generate approximately 2,800 megawatt hours per day, with an estimated value of around Rs16.6 million per year based on the current tariff of Rs5.94 per unit.

The most pressing challenge faced by farmers relying on canal irrigation systems is water scarcity during the dry season, which is further exacerbated by unpredictable climate patterns. Ensuring a consistent water supply for irrigation is crucial to maintaining agricultural productivity, as water shortages during critical crop growth stages lead to reduced yields and food insecurity. This issue is more pronounced in the tail regions. Considering these interrupted irrigation facilities, there is a diminishing number of labour and cash contributors, leading to a reduction in the surface irrigation system’s command area. These canals are not mere water channels; they serve as arteries that sustain our food production, rural livelihoods, social capital and economic stability and ameliorate the local ecosystems and groundwater recharge.

Opportunities and challenges

Solar panels, when strategically placed above irrigation canals, offer multiple benefits. The primary benefit is improving the system’s irrigation reliability by augmenting water in the dry season through groundwater pumping. The tail users of the system, who typically face water scarcity, benefit more from this arrangement. This improved water supply encourages farmers to shift towards market-oriented agriculture. Additionally, the energy generated can be used for value-added agricultural activities like processing, grinding, milling and cold storage, increasing the market value of products. Surplus energy can be fed back to the grid through net metering, supporting Nepal’s clean energy mission. As a result, income is generated for the irrigation system that can be spent for its repair and maintenance, which is vital for its sustainability.

Furthermore, canal-mounted solar panels create a cooler microclimate, shown to boost the efficiency of photovoltaic panels at temperatures between 25-35 degrees Celsius, leading to increased energy production. Moreover, the shade these panels provide significantly reduces water evaporation from canal surfaces. A similar approach in California is estimated to save 39,000 cubic metres of water annually per kilometre of the canal. Reduced evaporation not only conserves water but also benefits local ecosystems.

The proposed innovative approach hasn’t been piloted in Nepal. However, certain challenges are anticipated during implementation. First, there is no policy or regulatory framework for using canal areas for renewable energy-related infrastructure development, hindering the initiation and completion of solar projects on these canals. Transparent guidelines and legal frameworks are essential to facilitate canal land allocation for solar installations. Second, a cost-benefit analysis is vital to assess the economic viability of solarising irrigation canals, weighing upfront investment against long-term benefits like energy generation, water conservation, yield improvement and income generation.

Finally, blanketing Nepal’s extensive irrigation canals with solar panels offers huge advantages. It enhances energy access and availability in agriculture by improving irrigation reliability, higher crop production, greater farm income and improved food and nutritional security. It also ensures water access during dry spells, benefiting the often-affected tail users in the canals. This approach empowers water users by harnessing surplus energy through net metering, reducing water evaporation in the canals and optimising energy generation efficiency through cooling effect. Moreover, it simplifies land ownership complexities for installing solar panels on private land using canal land, which is predominantly public property. This is a win-win solution for Nepal’s transition to cleaner energy sources and an opportunity to address the challenges of the water-energy-food-ecosystem nexus.