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The Discovery of Green Water
Jan 1, 2016

The populations of cities, countries – and thus, the world – are constantly increasing. During the last two centuries, due to the impact of industrialization, human welfare has improved in parallel with a major leap in production and consumption.Improved welfare and booming populations have led to a rise in water consumption. This has led to more, and bigger, problems involving water pollution, conservation, and climate change. Many parts of the world have faced severe water shortages, including regions in Africa, China, India, and the Middle East. In many regions, thoughts of water dominate human interactions.

The major source of freshwater is, of course, rain. Rain is an extraordinary blessing given to humanity. It brings nutrients to our soil, nourishing trees and plants. It provides us with the hydration we need to live. But just as some rain is necessary, too much rain can be destructive. As with most things in life, we need a balance.

Green water

Let’s think of a rainy moment. While some portion of rain water flows over the ground’s surface, some is absorbed into the soil. A certain volume of the absorbed water is stored in the soil, but an excess amount then leaks further into the earth. With the aid of the stored water, the nutritional elements in the soil are dissolved and this solution is taken up by the roots of plants, thus enabling growth and development.

During this stage, while a small ratio of water remains in the plant, much of it passes into the atmosphere via transpiration. Even more water is lost from the soil via surface evaporation. This water goes into the atmosphere, and it then forms into precipitation.The portion of rainfall which is initially passed into the atmosphere through transpiration or soil evaporation is called green water (Figure 1). This concept was first proposed at a seminar of the United Nations Food and Agriculture Organization (FAO) in 1993.

Green water is a significant source of water and has a much larger volume than the water belonging to rivers, lakes, and aquifers, which are constantly refilled and replaced. This water is very important for land ecosystems. Rainfall-dependent crops, lumber, bio-fuels, and cotton all need green water.

Blue water

All floods, streaming waters, and ground springs that are not absorbed by soil make up what we call blue water. Blue water is utilized in irrigation, industry, energy generation, and housing. Aquatic and wetland ecosystems are dependent on this water. Blue water also carries solutions and silt which are used in river deltas, which help protect ecosystems, and can also be utilized – with the aid of dams – in hydroelectric power. As a great deal of water is needed for hydroelectric power, a shortage of blue water can lead to violence, or even war.

Blue water is the only source of hydroelectric power. It is used for other sources, too, but green water is far more abundant than blue. Thus, conservation efforts should be aimed at preserving and protecting green water.

Green water management

After a rainfall, depending on the vegetative cover, the permeability of the ground, and the slope of the water basin, anywhere from 5 to 95% of the water starts to flow. This ratio is called the flow coefficient. A lower flow coefficient means that a greater portion of the rainfall is captured by the soil; therefore, precipitation is efficiently used.

On the contrary, a bigger flow coefficient means that most of the water drains away and the rain is not properly utilized. In addition, excessive soil erosion takes place in places where there is more surface flow; as a result, areas without forest and vegetation develop. Over time, the surface flow increases, until no soil is left to hold water. Once soil is unable to absorb water, evaporation decreases, thus increasing the likelihood of a drought.

In heavily forested regions, the flow coefficient is usually between 5 - 20%. This number is around 5–35% for grass covered pastures, 30-75% in residential areas, and 70-90% for roads.

Water in soil is stored for plants

Even though the everlasting exchange among water, soil, and plants may seem very simple and ordinary, it is actually a wise, calculated, and balanced process. Without air, plant roots die because of hypoxia; without water, plants die from dehydration. In exchange for these blessings, roots support the soil, as if in expression of their gratitude. Without roots, water carries soil away. As a result of the cooperation among these three main elements, plants and clean water are constantly produced.

Unfortunately, this balance is at risk. Present field management practices show that rain water is not conserved and major losses are taking place. These losses happen in two ways:

  1. With flash floods and erosion causing high surface flow volumes;
  2. or via direct evaporation of water from barren soil.

After carefully considering the situation above, it becomes obvious that rainfall water must be conserved. The following steps can be taken to improve water conservation and crop production.

● Farmers can improve the local water balance. For this to be achieved, surface flow and erosion must be slowed down, soil absorption (or infiltration) should be enhanced, inefficient evaporation must be decreased, and water in the soil must be conserved.

● The water reserves of the lower basin are related to the upper basin through field management. If the water and soil of the upper basin are managed properly, the lower basin water sources become enriched, access to water becomes easier, water investment costs drop, floods decrease, and the cost of future preventive measures are lowered.

● The most important source of freshwater or clean water (blue water) is green water; as such, with better soil and water management, blue water can be regulated proficiently.

● Farmers play the key role in water management and should be supported. To do so, farmers must be educated; cooperative, union-like organizations must be formed; equipment should be provided for; and regulatory laws must be put in place.

Food shortages are perhaps the most severe consequence resulting from climate change. One way to help alleviate this problem is through better agricultural practices, especially in developing countries. Due to many factors, agriculture is a very local undertaking; it can be developed at the community level.

The key to improved agricultural production is better use of water. We must use water carefully, especially in places suffering from water shortages. Despite less rainfall, if already-present green water is well administered and locally suitable agricultural production is practiced, food shortages can be solved, and poverty at least somewhat alleviated. This can be achieved and maintained by educating people, informing them professionally, and supporting them via new technologies and improved infrastructure.

These measures should especially be adopted and implemented in dry or semi-arid regions like Turkey. This will help to preserve the already endangered water basins in these regions.

Looking at the water shortages around the world, it’s clear that we do not fully appreciate what a blessing rainfall is. We are wasting our water sources and destroying our soil. To help fight climate change and poverty, we must start giving this blessing its proper due.