4. Invisible water: Green water

What is the invisible water that saves food production in Africa?

When we think of water, we think of rivers and the water that comes from the faucets in our homes. The Falkenmark indicator is used to show the scarcity of the water we use; however, Prof. Falkenmark's interest gradually shifted to less obvious water. What type of water is this?
We use water for all sorts of things. It is necessary for our daily lives, industry and especially food production.

Prof. Falkenmark has been actively involved in the study of water issues in developing countries, especially those in Africa. It was there that she started looking at the influence of water scarcity on food production.
Since the 1960s, population has been growing rapidly in Africa. Africa is a very dry continent and does not have enough rivers to supply sufficient water to support the population. Even if they want to cultivate agricultural products, it is impossible for the regions that are away from rivers because irrigation is impractical. What can they do to produce more food in Africa?

When Prof. Falkenmark was checking data, she noticed certain characteristics of water scarcity in Africa. It occurred not in tropical rainforests like the Congo, but in the surrounding savannas.
Here are five maps that Prof. Falkenmark created. Each map shows these characteristics by country and region.






Click to enlarge

Looking at these five maps, we realize that they are very similar. While creating these maps, Prof. Falkenmark discovered that areas with one serious issue usually have other serious problems as well.

She also suspected that the key to solving these problems may be the water contained in soil. Rainwater runs along the surface of the ground. Some drains into rivers and some is absorbed into the soil. Prof. Falkenmark focused on the fact that the water used by agricultural products and other plants is water absorbed by the soil.
Agricultural crops are not grown in rivers. Plants absorb water contained in the soil through their roots. Water travels up to the leaves through the stems. When leaves absorb CO2 through their pores for photosynthesis, the water is discharged into the air (transpiration). As described above, water contained in soil is essential for plants.

Prof. Falkenmark decided to call the water contained in soil and used by plants "Green Water," and the water in rivers and underground used for irrigation "Blue Water."

Blue and Green Water

Blue and Green Water

Prof. Falkenmark divided water used in food production in Africa and other dry regions into blue and green water. She saw green water as more important and felt the need to change our existing ideas about water. She felt blue water should be used for living and industrial use while green water should be used for agricultural, which means food production.
Prof. Falkenmark advocated the concept of green water at the Food and Agriculture Organization (FAO) meeting, and the concept was highly regarded. She thinks that green water should be the priority. It goes without saying that fertile soil is important for plant growth; however, the focus has always been on the nutrients in soil rather than on the water required for roots to take in those nutrients. This focus has not changed much.

Only about 30% of the rainwater that falls during the rainy season in Africa ends up being used. If we can collect and store the remaining 70% for use during the dry season, food production may increase. In order to achieve this, it is necessary for us to develop water supply methods and storage technologies.

At Victoria Falls (in 1990s)

At Victoria Falls (in 1990s)

SDGs and green water

Sustainable Development Goals (SDGs) was adopted by the United Nations General Assembly in 2015. Among the 17 SDGs, Goal number 2, "Zero Hunger," is the stable supply of food and the promotion of sustainable agriculture.

In 2017, the United Nations published its SDGs wedding cake model, which classified the 17 goals into three layers. This model has four natural capital SDGs, "clean water and sanitation," "climate action," life on land," and "life below water." All other SDGs are to be achieved with natural capital as the base.

SDGs Wedding Cake Model

SDGs Wedding Cake Model
Click to enlarge

Stockholm International Water Institute (SIWI), where Prof. Falkenmark works holds World Water Week in August of each year. One event held during the week is the Falkenmark Symposium, which is named after the professor.
Through the symposium, she has asked for support from around the world to help people understand that the biggest SDG, "No Hunger," can be achieved by crop production, and that the use of green water for this is essential.

Water is the origin of everything on the Earth

Prof. Falkenmark has been actively engaged in research on the role of water in ecosystems. The role of water in trees and plants in ecosystems has not been sufficiently understood and appreciated.
Prof. Falkenmark has worked on implementing the green water concept into SDG number 6 "clean water and sanitation." This promotes activities to preserve and restore water in ecosystems in mountains, forests, and wetlands. She has continued working passionately on this.

She enjoys spending time on weekends with her grandchildren. She hopes young children will have an opportunity to learn about global water issues at school.
Young children like to play in the water, but adults tend to forget the feeling. Because young children are very interested in water, Prof. Falkenmark wants them to learn that it is the origin of all life on the Earth.

Winners Memorial Lecture


Prof. Malin Falkenmark