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.
When making a hydrological map, it is necessary to evaluate the accuracy of the obtained map and specify it on the map. The author has studied the spatial correlation of monthly precipitation and proposed a method of expressing the accuracy of monthly precipitation map by using spatial correlations. The calculation of spatial correlation is done among all the stations over the area. The accuracy is measured by the maximum value which is smaller than any actual correlation coefficients between all the neighboring observation stations. The data used in the analysis are the monthly precipitations observed in the northern and the middle parts of the Kanto District from January 1961 to December 1970. Iso-lines of spatial correlations of monthly precipitation are shown in Figs. 1_??_5. There are some distinctive features in the patterns of iso-lines. The iso-lines of 0.90 and 0.95 are not always circular but slender except the case of iso-line map for Tokyo. The area of the closed iso-lines of spatial correlations is large in the middle part of the Kanto Plain, and small in the area adjacent to the mountainous area. It is important to arrange the observation stations by the synthetic consideration of spatial correlations of the precipitation.
In this paper, the authors propose a method of standardizing a number of first-order streams and a drainage density for different map scales. Measurements of channel network are done at 8 drainage basins in the Kanto District, using topographic maps with the scales of 1:25, 000 and 1:50, 000 in order to analyze effects of map scale on characteristics of channel network. There are some differences between channel network drawn from 1:25, 000 and 1:50, 000 as shown in Figs. 1 and 2. Results of measurement at 8 drainage basins are shown in Table 1. The ratio of the number of first-order streams between 1:25, 000 and 1:50, 000 maps is about 2.0, and the ratio of the drainage density is about 1.4. The number of the first-order streams and the drainage density are smaller in the smaller scale map. On the contrary, the ratio of the average length of the first-order streams is about 0.7 and the ratio of the average drainage area of the first-order streams is about 0.5. The average length and the average drainage area of the first-order streams are larger in the smaller scale map. In general, however, the parameters of Horton's law are not affected by map scale (Fig. 3). The ratios of the average length of the first-order streams, the average drainage area of the first-order streams and the drainage density between different map scales are derived as a function of the ratio of the number of the first-order streams (Eqs. (9), (10) and (12)). The calculated ratios and the measured ones are summarized in Table 3. For analyzing the channel networks, it is important to indicate the map scale used in the analysis, and if one needs the comparisons between the values from the different map scales, the conversion by Eq. (14) could be possible.
A hydrological map is one of the most effective tools to express hydrological phenomena, especially spatial distribution of hydrological variables. Since different expressing or processing procedures for one statistic or variable might give different information, we have to consider how to express concerned hydrological elements. In this paper, the author tries to show differences of information in three different expressions for one statistic and to analyze them from a statistical point of view. As a statistic, taken are the minimum values of annual precipitation at 85 stations over Japan (in Fig. 1); the minimum values are expressed by three different ways, that is, observed values xmin, normalized values zmin, and modular coefficients kmin. The observed values are minimums during observation periods, which are different but longer than 40 years as shown in Table 1. The normalized values are defined by Eq. (1). As long as annual precipitation is normally distributed, these values can be compared under the absolutely common standard. The third values, modular coefficients are defined by Eq. (2). These three values are generally used to express hydrological variables. Distribution maps of minimum values of annual precipitation by the three ways are shown in Fig. 2, which shows different distribution patterns. This means that these three values for one statistic might not be equivalent in information content. Relationships between z and k, which are function of coefficient of variation (Eq. (3)), are discussed statistically. Under normal distributions, z and k are statistically equivalent only when mi=mj and si=sj, or si/mi=sj/mi, where i and j denote stations. For the former case, xi=xj, but for the latter, xi≠xj. Otherwise, they are not in one-to-one correspondence as shown in Fig. 3. This means that isolines of modular coefficients are not always significant statistically. Therefore, distribution map by modular coefficients in Fig. 2 has many closed areas, which notifies spatial discontinuity among individual values. Under non-normal distributions, when si/mi=sj/mj, z and k are just equivalent in one-to-one correspondence. However, they are not compared under the absolutely common standard. As a conclusion, we have to consider well whether or not isolines are meaningful for the concerned variables as well as extreme values, because even equal values are not always equivalent in statistical means.
The Tone river system has long been utilized as one of the major water resources for Kanto district, but the situation becomes serious due to human impact on the river system. Recently. the utility value of the river system is enhanced with the demands of water supply which have an increasing tendency year by year. In order to estimate the utility value at present and in future, the changes of river regime of the Tone river system should be clarified. The purpose of this paper is to show the changes of the river regime and to delineate a hydrological map. The data used in this paper are the annual total discharge, the annual mean discharge, the minimum discharge, the maximum discharge, the monthly discharge, the annual rainfall, and the monthly rainfall from 1938 to 1977; these data were obtained by the River Bureau, the Ministry of Construction (The Civil Engineering Bureau, the Ministry of Interior was in charge before the World War II). The mean values of these data were calculated in every ten years and during forty years since 1938 (Tables 1 and 2). The time variations of run-off, run-off percentage, coefficient of river regime, and loss were calculated (Table 3). The thirty-two discharge and thirteen rainfall gauging stations were selected to present the river regime. The changes of river flows of the major rivers were shown in Figures 1 through 7. Figure 8 shows the hydrological map of the regime with the annual total discharge, the non-dimensional hydrograph, the run-off percentage, and coefficient of river regime. The results of this work are summarized as follows: 1. The Tone river system can be hydrologically divided into two groups except the Katashina River and the upper reach of the Tone River which are rather unique in their flow regime. The one group embraces the Kokai, the Kinu and the Omoi Rivers and the other includes the Watarase, the Agatsuma, the Karasu, the Usui, and the Kabura Rivers. 2. Although the main stream of the Tone River has presented the various changes during the last forty years, the others have fairly constant values. 3. The hydrological map cannot perfectly have a function as a general one because of the difficulties of making techniques. 4. It is recommended that we had better use various kinds of colors in expressing the variations of river flows.
Recently many kinds of water quality data have been collected by the Environmental Agency, the Ministry of Construction and so on, but these data are not necessarily systematic. As the first step, authors rearrange these water quality data, especially BOD and COD data collected by the Environmental Agency, for the analysis and mapping. Through this process, the characteristics of the water quality data, the structure of the data, and difficulties of the standardization of the data were discussed. A necessity of water quality maps was mentioned for a rational design of the countermeasures against water pollution. An importance of compilation of related data such as river discharge, geomorphological factors and pollutant sources besides water quality data was also pointed out. As an example of a hydrological map of water quality, authors tried to draw up two distribution maps: BOD concentration over the rivers of Kanto District as shown in Fig. 2 and temporal changes of BOD and COD at the major water bodies over Japan in Fig. 3. Figure 2 shows annual mean concentrations of BOD given by the arithmatic mean of measuring points where more than 9 daily mean values were recorded in 1978. This figure shows that the large rivers such as the Ara, the Tama, and the Sagami Rivers in the metropolitan area have BOD concentration of 3_??_8ppm, which indicates recent improvement of water quality. However, at the midium and small rivers in the area BOD concentration shows terrible conditions with values of above 10ppm. On the other hand, the upper parts of the Tone and the Naka Rivers are still keeping a good water quality of about 1_??_2 ppm. These facts reflect the history of water pollution control policy in Japan and also imply what kinds of measures or controls are needed. However, in order to clearly understand circumstances of water quality or water pollution, more information such as water use, hydrological conditions and geomorphological factors should be included in the map. In Figure 3, the annual mean concentrations of BOD and COD of rivers, lakes and coastal seas in Japan during 1971 and 1974 are compared with those during 1975 and 1978. Water quality of most rivers where high concentrations were recorded during the first period was improved very well at the second period. However, improvements at lakes and coastal seas could not seen. These regional characteristics and differences among different water bodies of water pollution and its control suggest the necessity of a new policy and countermeasures against water pollution. As a concluding remark, systematic arrangements of water quality data collected by many different organizations and their expression as hydrological maps give a great help to water quality control.
Using satellite remote sensing data, the system for predicting soil moisture contents and mapping of its distribution was investigated in this paper. It was necessary to observe environments and to collect the data in the field for the numerical analysis of remote sensing technique. Since a collection period of ground truth data (landuse and soil samples) was desirable to coinside with satellite (LANDSAT-3) overpass (Jan. 1980), the collection was carried out for 4 days (Jan. 17_??_20, 1980) in the Kujukuri coastal plain. Procedures of this system were based on multivariate statistical analysis and computer mapping techniques. The data were processed by means of a multiple discriminant analysis for classification of landuse and a multiple regression analysis for estimation of soil moisture contents, where the soil moisture contents is a dependent variable and the remote sensing parameters are independent variables. Above mentioned processes and automatical mapping with LANDSAT data brought the following conclusions. 1. Some problems (e. g. performance of classification and efficiency of modelling) to be solved in the processing of the future data were indicated. 2. Distribution of soil moisture contents showed NNE-SSW linear pattern subjected to the developments of the micro-topographies such as emerged bar, sand spit and dunes in the Kujukuri coastal plain. 3. The region such as Hasunuma, Naruto, Ohamishirasato-Honno and Shirako were under higher soil moisture contents. In particular, at Shirako and its vicinity on the lower Nabaki which was major subsiding area, submerged paddy field and exposed ground were observed. 4. Soil moisture contents reduced from Shirako and its vicinity to Kujukuri. 5. On the other hand, the soil with higher moisture contents were originated with shade behind the valley wall or restricted drainage with barrier, whichever artificial or not, in the valley plain and the rear of the coastal plain. 6. It is expected that these soil moisture contents models had to be revised in the future analysis and satellite remote sensing might offer practical potential for the thematic mapping and the monitoring of the environments.