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Towards an Ensured and Sound Hydrological Cycle

By Seiji IKKATAI, Director
Water Quality Management Division, Water Quality Bureau
Environment Agency, Government of Japan

Introduction

The policy concept of an ensured and sound hydrological cycle was established in 1994 by Japan’s Basic Environment Plan. The national policy to ensure sound water cycles is very important, but realization of the policy is complicated by the fact that it is not easy to coordinate the relevant policies of each Ministry and Agency in charge of various water management issues.

In March 1999, after one and a half years of intensive discussions that included public comments, the Central Environment Council, an advisory board of the national government, published a report titled “The Basic Concept and Policy Measures for Ensuring a Sound Hydrological Cycle” and submitted it to the Director General of the Environment Agency. The Environment Agency is currently formulating policy measures in response to this report. In addition, the Environment Agency and five other Ministries and Agencies have established an inter-Ministerial working group in order to form a common approach for better management that leads towards ensured and sound hydrological cycles.

This paper presents an outline of the March 1999 report and also describes the progress of the ongoing discussion among the Ministries and Agencies concerned.

I. Outline of the March 1999 Report

1. Basic Background

A sound natural hydrological system maintains a vast variety of ecosystems; it purifies water and tempers extreme meteorological conditions because of the specific heat capacity of water and evaporation from vegetation and water surfaces. The natural water cycle transports heat and substances and is available to support many of humankind’s uses. We know that such healthy hydrological cycles are necessary to ensure human survival, both physically and spiritually.

Japan’s actual hydrological cycle of today has been created by adding human-made, artificial hydrological processes to the natural hydrological system. These artificial systems were created to secure effective societal water use and to protect against floods. For example, rice paddies, the most traditional form of agriculture in Japan, use the water from rivers. The water feeds not only the rice but also beautiful local ecosystems; then the water reenters the river once again. This is a case where the artificial hydrological cycle is in harmony with the natural hydrological cycle. But of course, not all cases of artificial water cycles reflect such harmony.

2. Background of Deterioration

The concentration of the Japanese population in urban areas and the resulting rapid development of these areas since the mid-century have resulted in many changes to the hydrological cycle. The size of the area where rain cannot permeate the ground has increased, and the area for forests and rice paddy fields has decreased. This has caused destruction to part of the natural water cycle, which has in turn resulted in unstable water flow rates, depletion of the water in wells and springs, deterioration of ecosystems, and various other problems.

In other words, rapid urbanization and improvements in living conditions produced huge water demands for use in peoples’ daily lives, industry, hydro-electric power plants, etc. It also produced the need for public works designed to prevent floods. During this time, the government concentrated its efforts on the solution of sectorial issues by separate agencies, not on the development of comprehensive measures that would help ensure sound hydrological cycles. The result of this rapid urbanization and segmented government approach is that there are now many artificial hydrological systems that do not function in harmony with the natural water cycle.

3. Examples of Various Kinds of Deterioration

Forest Areas

The decrease in the size of virgin forests and poor forest management have lessened the previous natural capacity of forests to contribute to healthy water cycles in such ways as replenishing and maintaining ground water levels.

Agricultural Areas

Decreasing the area for farmland, especially rice paddies, has resulted in a decline in filtering functions that previously enhanced water purification, as well as the replenishment and storage of groundwater. In addition, the excessive use of fertilizer and pesticides has caused ground water pollution.

Urban Areas

Permeation of water into the ground is currently hampered by the asphalt pavement and storm water drainage systems associated with urbanization. Consequently, there are such problems as intensified fluctuation in the flow of rivers (i.e. floods during heavy rains and unnaturally reduced flows during periods of normal precipitation), dried up springs, and a lowered capacity to purify water. The quality of river waters in urban areas remains degraded, and the health of aquatic ecosystems has deteriorated. In addition, heat island phenomenon has been recorded in major urban areas.

Coastal Areas

Seaweed beds and shallow water areas have decreased because of development. The natural supply of sand and soil from rivers has been changed by the construction of dams and other water projects.

4. Basic Concept for an Ensured and Sound Hydrological Cycle

A “sound hydrological cycle” exists when the benefits derived from the natural hydrological cycle have basically not been diminished.
To ensure such a state, efforts should be made to minimize the impacts of human activities and to maximize the sustainable functions of the natural hydrological cycle.
Important issues which should be considered simultaneously are:

1. The scope of a “sound hydrological cycle” includes not only surface water but also ground water. We should understand the watershed as a dimensional structure.
2. Increases in water demand and water contamination created conditions that led to the deterioration of the natural hydrological cycle. Thus, technology development that makes the goals of water use and water conservation compatible must be stressed. At the same time, activities the result in the reuse and saving of water should also be emphasized.
3. Public works to address flood control are inevitable, but environmental considerations that make flood control and sound hydrological cycles compatible must be integrated more and more into these public works.
4. Policies regarding sound hydrological cycles should not increase the consumption of fossil fuel or natural resources, rather, they should result in the use of more renewable energy sources.

Table of Contents

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• International Year of Forests
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