Irrigated agriculture is responsible for 70% of the world’s freshwater withdrawal, largely due to the highly wasteful method of flood irrigation. It is the key sector to be addressed by policy makers to enable a change if it is supposed to be truly effective.
The key term is water use inefficiency, which means the techniques of irrigation are characterized by a loss of water by far exceeding the water reaching the plant. The water which is pumped from a river or aquifer (groundwater) is wasted by more than 50%, often 80 to 90%.
Water use inefficiency is the outcome of water management guided by the paradigm that the adequate response to rising water demands is the augmentation of water supplies through engineering measures. That happens in most countries in the world. It is called water supply management. Water supply management 'generally means that governments make available freshwater at the lowest cost possible to people, farmers and industries, usually exploiting freshwater sources to the fullest.'
It implies the total neglect of the demand side. In the supply driven approach the capital, operation and maintenance costs of the supply system (from the source to the user) are the only parameter taken into account in the cost calculation. The water itself is not given an economic value, contrarily it is even subsidized. System costs cannot be recovered as revenues are nil or very low, maintenance is neglected, the systems deteriorate and as explained above water losses often exceed the delivered water by far. Water is regarded an infinite resource which does not need to be saved or regulated in quantity. At the point where the water is consumed (crop production) it is then applied without considerations of efficiency.
The water user (land manager, farmer) plays a passive role. They are made exempt of any responsibility for the sustainability of their production system which is provided with high fuel and water subsidies and other financial favors and supportive state measures. 'A system based on securing supply creates excess demand' says the World Bank.
Contrarily water demand management is based on the principle that water has an economic value and should be recognized as an economic as well as social good. It is key to attaining a sustainable water allocation where water is scarce and it is the fourth of the Dublin Guiding Principles formulated in preparation for the World Summit in Rio 1992: 'Water has an economic value in all its competing uses and should be recognized as an economic good - Past failure to recognize the economic value of water has led to wasteful and environmentally damaging uses of the resource. Managing water as an economic good is an important way of achieving efficient and equitable use, and of encouraging conservation and protection of water resources.'
Water demand management encourages water saving, water efficient production and water allocation which is most beneficial and profitable to society. Water for any kind of human activity is a social or economic good, as human health, ecosystem health, marketable goods. Water should ideally be allocated to high-value uses as otherwise it constitutes a loss to the well-being of society.
Agriculture is necessary as it is the sector producing our food. There are two groups of crops to be distinguished: Staple crops and cash crops. Staple crops form the base of a country's and culture's diet as rice in South East Asia and Latin America, wheat for bread and pasta etc., potatoes, corn, soy. Cash crops are cultivated on significantly smaller proportions of land, in that group you find coffee and tea, all tropical fruits and cocoa, tomatoes as well as all other vegetables, also sugar cane, tobacco and cotton.
The following figures are derived from the FAO's Aquastat. Only 20% of the global surface used for crop production is irrigated, thus 80% of crops are grown under the natural conditions of rainfall. On the 20% irrigated land 40% of our food is produced. Irrigation takes place where the climate is dry or longer dry periods exist, but also in temperate climates as an addition. On a global scale 86% of all irrigation is flood irrigation, also called surface irrigation (2012 figure). The remaining 14% apply techniques of micro irrigation, such as drip irrigation which is highly efficient as the water actually reaches the plant and losses are low.
Thus, 20% of the total agriculture area worldwide require 70% of the total water used by humanity, under the current scenario of 86% surface irrigation.
Referring back to the two crop groups of staple and cash crops, I want to point to the high complexity of agricultural planning and thus water planning. Countries grow staple crops to gain independence of food imports at least for the basic necessity of providing food to their population, whereas cash crops mostly but not always provide larger revenues due to higher market prices and they are by nature less important for basic human nutrition. A country is only in the position of dedicating land to growing cash crops when they are fully able to provide full plates to their population, as food imports of the basics as rice, wheat etc. always constitute a weakness in the economic and social system. However, regional food imports are from the view point of improved water planning a crucial mechanism to manage water more sustainably. However, the regional players (countries) have to have developed a large trust among one another to allow for that regional exchange of basic human necessities to occur.
Micro irrigation technology is usually installed on cash crop plantations. To globally reduce water waste it is the production of staple crops which has to become more efficient in its water use.