Irrigation dates back to roughly 6000 BC, when the waters of the Nile and Tigris-Euphrates were first diverted to feed farmers’ fields. Today, agriculture consumes 70 percent of the world’s freshwater resources, and irrigation is essential for 40 percent of the world’s food production. Because pumping and distributing water requires large quantities of energy, irrigation is a source of carbon emissions.
Irrigation technologies have evolved to help farmers use water more precisely and efficiently. Both drip and sprinkler methods make water application more exact, delivering as precisely as possible the amount crops need to thrive. With 70 to 90 percent application efficiency, they reduce overall water and energy consumption.
The benefits of drip and sprinkler irrigation are numerous: crop yields improve, costs drop, and soil erosion declines. Lower humidity curtails pests. Surface and groundwater resources are better protected, and conflicts among various stakeholders for water resources may ease. However, both systems require infrastructure and upkeep, which can be expensive, sometimes prohibitively so.
Other practices and technologies can also be effective. Irrigation scheduling and deficit irrigation are two methods of variable application. Sensors can monitor soil moisture and control irrigation systems automatically. Rainwater and runoff can also be captured and put to use.
6000 BC… Egyptians and Mesopotamians: Stewart, B. A., and Terry A. Howell. Encyclopedia of Water Science. New York: Marcel Dekker, 2003.
agriculture and irrigation consume…freshwater: World Water Assessment Programme. The United Nations World Water Development Report 4: Managing Water under Uncertainty and Risk. Paris: United Nations Educational, Scientific, and Cultural Organization, 2012.
irrigation is essential for…food production: World Water Assessment Programme, Managing Water.
[water] application efficiency: Phocaides, Andreas. Handbook on Pressurized Irrigation Techniques. Rome: Food and Agriculture Organization of the United Nations, 2007; Sauer, T., P. Havlík, U. A. Schneider, E. Schmid, G. Kindermann, and M. Obersteiner. “Agriculture and Resource Availability in a Changing World: The role of Irrigation.” Water Resources Research, 46 (2010).
farmland under drip…irrigation: Starke, Linda, Erik Assadourian, and Tom Prugh. State of the World 2013: Is Sustainability Still Possible? Washington, D.C.: Island Press, 2013.
4 percent of…irrigated land: Starke et al, State.
Asia [has] significant opportunity: Aquastat. “Irrigation and Drainage.” Food and Agriculture Organization of the United Nations. http://www.fao.org/nr/water/aquastat/irrigationdrainage/index.stm#reg.
Project Drawdown defines farmland irrigation as: a set of energy-efficient irrigation practices that increase crop yields while reducing emissions. This solution replaces conventional irrigation on irrigated cropland.
Pumping and transporting water accounts for 70-80 percent of global water use, and is a major use of energy. Much of this irrigation is delivered using inefficient methods such as flood irrigation. Employing improved farmland irrigation practices across the agricultural system can bring about water and greenhouse gas savings as high as 25 percent and 40 percent under sprinkler and drip methods, respectively, compared with conventional irrigation methods.
Of course, irrigation is critical to crop production, particularly in the era of climate change with increasingly unpredictable rains. For this reason, efficient irrigation is highly rated as a climate change adaptation strategy.
Total Land Area 
The total land area for this solution is irrigated cropland, totaling 246 million hectares.  Current adoption  of efficient farmland irrigation is 44 million hectares, based on the country-level figures from the International Commission on Irrigation and Drainage (ICID, 2015). The country-level figures were aggregated at the regional level. Maximum current adoption of the solution was found in the Organization for Economic Cooperation and Development (OECD) region (24.3 million hectares), while Asia, the largest consumer of irrigation water, has the lowest adoption (6 million hectares.
Adoption Scenarios 
Five custom adoption scenarios were developed based on the aggregated region-level data. Some of the custom adoption scenarios assume higher growth rates for all regions except the OECD, which has a much higher current adoption than other regions. Considering global water scarcity, two of the aggressive adoption scenarios assume a 100 percent conversion of the conventional irrigation system to micro-irrigation systems, with one scenario assuming an early peak adoption by 2030.
Impacts of increased adoption of farmland irrigation from 2020-2050 were generated based on three growth scenarios, which were assessed in comparison to a Reference Scenario where the solution’s market share was fixed at the current levels.
- Plausible Scenario: Analysis of these five custom scenarios results in the adoption of 181.5 million hectares for farmland irrigation under this scenario.
- Drawdown Scenario: This scenario results in 100 percent adoption – i.e., of 246 million hectares – by 2047.
- Optimum Scenario: This scenario results in 100 percent adoption by 2043.
Climate impacts of farmland irrigation are based on the difference between the electricity required per hectare for conventional and improved irrigation systems. Meta-analysis of Food and Agriculture Organization (FAO) data found that conventional irrigation requires 2.3 terawatt-hours per million hectares per year, while improved irrigation uses 1.5 terawatt-hours per million hectares per year.
Conventional first cost for irrigation is US$671.37 per hectare,  based on 13 data points from 10 sources. First cost for the farmland irrigation solution is US$1,575.86 per hectare, based on meta-analysis of 37 data points from 22 sources. Conventional net profit margin is US$407.46 per hectare, based on 38 data points from 22 sources. Net profit margin per hectare for farmland irrigation is US$152.02, calculated by adding the net profit margin of the conventional practice to the difference between conventional irrigation costs and the weighted average cost of micro-irrigation.
Unlike most Drawdown solutions, the farmland irrigation solution can be applied to units of land where other solutions are taking place, as it was determined that the emissions reduction from improved irrigation is independent from, for example, biosequestration from conservation agriculture or tree intercropping.
Total adoption of farmland irrigation in the Plausible Scenario is 181.5 million hectares in 2050, representing 40.8 percent of the total available land. Of this, 100.5 million hectares are adopted from 2020-2050. The emissions impact of this scenario is 1.3 gigatons of carbon dioxide-equivalent reduced by 2050. Net cost is US$216.2 billion. Net savings is US$429.7 billion. This solution also reduces water use by 340.6 billion liters from 2015-2050.
Total adoption in the Drawdown Scenario is 246.0 million hectares in 2050, representing 100.0 percent of the total available land. Of this, 202.0 million hectares are adopted from 2020-2050. The impact of this scenario is 2.3 gigatons of carbon dioxide-equivalent reduced by 2050.
Total adoption in the Optimum Scenario is 246.0 million hectares in 2050, representing 100.0 percent of the total available land. Of this, 202.0 million hectares are adopted from 2020-2050. The impact of this scenario is 2.3 gigatons of carbon dioxide-equivalent reduced by 2050.
Few benchmarks are available to provide comparisons for this study. The FAO noted in 2011 that no published figures were available on greenhouse gas emissions from irrigation (Turral et al., 2011).
Additional data points on the emissions and irrigation costs of farmland irrigation would improve this study. It would also be worthwhile to model extending improved irrigation to currently rainfed areas to increase yields as a form of agricultural intensification.
Irrigation efficiency is a win-win solution. It increases food security in a world with increasingly unpredictable weather, reduces water use, and reduces emissions.
 To learn more about the Total Land Area for the Food Sector, click the Sector Summary: Food link below.
 Determining the total available land for a solution is a two-part process. The technical potential is based on the suitability of climate, soils, and slopes, and on degraded or non-degraded status. In the second stage, land is allocated using the Drawdown Agro-Ecological Zone model, based on priorities for each class of land. The total land allocated for each solution is capped at the solution’s maximum adoption in the Optimum Scenario. Thus, in most cases the total available land is less than the technical potential.
 Current adoption is defined as the amount of functional demand supplied by the solution in the base year of study. This study uses 2014 as the base year due to the availability of global adoption data for all Project Drawdown solutions evaluated.
 To learn more about Project Drawdown’s three growth scenarios, click the Scenarios link below. For information on Food Sector-specific scenarios, click the Sector Summary: Food link.
 All monetary values are presented in US2014$.
 For more on Project Drawdown’s Food Sector integration model, click the Sector Summary: Food link below.
Full models and technical reports coming in late 2017.