Research Trends and Results
Construction of a Sound Water Cycle in River Basins-- Efforts for Proper Use and Conservation of Ground Water -KAWASAKI Masaki, Head; NISHIMURA Sorin, Senior Researcher
Water Cycle Division, River Department
Keywords: water cycle, ground water, ground water management, local government, flow analysis, field survey
1. Introduction
In view of the forecasted increase in draught risk due toclimate change, the rise in water demand due to theglobal increase in population, and intensifying
competition in the water business, attention is being paid
to "sound water cycles" to keep in place the roles of waterin human activities and environmental conservation.
Amongst the various factors that play into a water
cycle, concern is being raised about uncontrolled
development of ground water since it is characterized as
private rights incidental to land and not well managed as
river water. In addition, since ground water is a goodand inexpensive water resource as seen in the recent
increase in preference for mineral water, efforts arerequired to ensure proper use and conservation of groundwater.
2. Ground water management
Ground water is generally characterized by goodquality, little change in water temperature and no need forlarge storage, intake or supply facilities owing to intake
from wells. Japan has many alluvial plains and fanswhere gravel layers containing much ground water havedeveloped, so ground water has been widely used sinceancient times and supported the life of people.
Meanwhile, there has not been great progress in the
management of ground water because there are two
opposing concepts, i.e., the "concept of water as a publicresource," which would require that ground water beregulated by public law since it constitutes the foundationof the environmental function of land including
surrounding areas, and the "concept of water as a private
asset," by which ground water belongs to private property
since the land owner may construct a well to use waterfor private purposes.
In recent years, however, in view of the necessity toprevent uncontrolled development of ground water andpromote sustainable use of ground water, in themunicipalities where ground water use is advanced, suchas Kumamoto City (Kumamoto Pref.) and Ono City(Fukui Pref.), recognition of ground water as public
property is being developed through continued
environmental education and information dissemination.
And, ground water management has been strengthened
and/or upgraded.
3. Outline of the study(1) Field survey on ground water management
and systematic organization of advanced

cases
Using questionnaire surveys for prefectures andmunicipalities, we want to grasp the status of groundwater management in the country and identify issues, andexamine measures for strengthening / upgrading groundwater management for the areas where ground water
management is advanced, such as Kumamoto City andOno city. We intend to organize and summarize
methods and concepts of ground water management
systematically as reference for other local governments.
(2) Cross-sectional organization of the cases ofground water flow analysis
Ground water flow analysis is an important tool thatvisually clarifies, as shown in the table below, the groundwater flow characteristics of the relevant region based on
surface water and ground water flow models, and serves
as basic information for the governance of ground water,
including hydrologic processes such as rainfall andsurface runoff, underground penetration, flow of groundwater into rivers, leakage of river water into theunderground, and pumping. However, the accuracy of theanalysis is low due to insufficient data on the pumping
discharge of ground water, nature of the soil, etc. It is,therefore, necessary to take into account suchinaccuracies in order to properly handle analysis results.
For these reasons, we intend to collect data on the casesof ground water flow analysis conducted by MLIT acrossthe country and cross-sectionally organize the accuracyetc.
Rainfall, etc.
Undergroundpenetration

Surface runoff

Cultivation
River runoff
Equivalent roughness
coefficient etc.

Water retention in land

Spring
Surface water model
Flow of spring into the river

River runoff
Flow of ground water into the riverAchievement
model

Leakage of river water into the undergroundPumping
Ground water flow

Ground water flow model

Integrated analysis

Coefficient of permeability,etc.

Achievement
model

Figure: Conceptual Diagram of Ground Water
Flow Analysis