水文環境の地図化とその問題点 水文環境地図特集号に寄せて

抄録

A great number of hydrological studies have recently been done and presented in various fields. If these achievements can be represented in the form of maps, their use will be of a remarkably wide range. The research group of hydrological map was organized in October, 1976 (replaced by the working group in April, 1979) as one of the commissions in the Association of Japanese Geographers to discuss how to map the hydrological environment. The summary of the commission activities is as follows.
The regular meeting for research was held 23 times; the annual report, Researches on Hydrological Map was published twice (No. 1, 1977 and No. 2, 1978). Seven papers were presented for IGU-IHP Commission Symposium, 1980 IGC. The group also set up such subjects for study as “The definition of the map of hydrological environment and methods of mapping hydrological elements”, “Mapping of hydrological environment on a middle scale”, and “Mapping of hydrological environment on a large scale” and has been making researches in concrete work. The results of the study were presented in Studies on Mapping Hydrological Environment (Grant-in-aid for co-operative research (A), The Ministry of Education, Science and Culture, Japan 1980).
The purpose of the present study is to attempt to decide methods of mapping hydrological environment. Before entering into the main subject, the author refers to the definition of the map of hydrological environment: the map reflects all kinds of hydrological phenomena around earth's surface presented by complex actions of natural factors and human impacts in relation to the earth's hydrological cycle.
It is the most important work in mapping to select carefully proper factors for representing on a map from a large amount of information and to develop a method of representation as rational as possible. In other words, the legible representation of carefully selected elements of hydrological phenomena is the key to mapping hydrological environment.
Hydrological phenomena are classified into three groups according to the situation in which the phenomena occur: one in the atmosphere, the second on the earth's surface and the last in the underground. The principal hydrological elements in the first group are precipitation, probable precipitation, rainfall intensity, evapotranspiration, potential evapotrans iration temperature, etc.; in the second, topography, river, lake, soil, vegetation, land use, etc.; in the last, hydro-geology, groundwater, etc. As it is impossible both in quality and in quantity to map the hydrological environment embracing all those phenomena. The description of the elements should be confined to the irreducible minimum and the most proper method of representation should be decided according to the object of the map. However, there still remain some problems such as, which scale to use in drawing base map, how to represent the distribution of groundwater use, and how many ranks to use in showing the different elements on the same map.