stylistic:tone
Modern history

The scale of irrigation increased dramatically over the 20th century. In 1800, 8 million hectares globally were irrigated, in 1950, 94 million hectares, and in 1990, 235 million hectares. By 1990, 30% of the global food production came from irrigated land. Irrigation techniques across the globe included canals redirecting surface water, groundwater pumping, and diverting water from dams. National governments led most irrigation schemes within their borders, but private investors and other nations, especially the United States, China, and European countries like the United Kingdom, funded and organized some schemes within other nations. Irrigation enabled the production of more crops, especially commodity crops in areas which otherwise could not support them. Countries frequently invested in irrigation to increase wheat, rice, or cotton production, often with the overarching goal of increasing self-sufficiency. In the 20th century, global anxiety specifically about the American cotton monopoly fueled many empirical irrigation projects: Britain began developing irrigation in India, the Ottomans in Egypt, the French in Algeria, the Portuguese in Angola, the Germans in Togo, and Soviets in Central Asia.

Negative impacts frequently accompanied extensive irrigation. Some projects which diverted surface water for irrigation dried up the water sources, which led to a more extreme regional climate. Projects that relied on groundwater and pumped too much from underground aquifers created subsidence and salinization. Salinization of irrigation water in turn damaged the crops and seeped into drinking water. Pests and pathogens also thrived in the irrigation canals or ponds full of still water, which created regional outbreaks of diseases like malaria and schistosomiasis. Governments also used irrigation schemes to encourage migration, especially of more desirable populations into an area. Additionally, some of these large nationwide schemes failed to pay off at all, costing more than any benefit gained from increased crop yields.