Yemen Arab Republic is located in the south-western corner of the Arabian Peninsula. The area lies between parallels of latitude 12°30' and 17°30'N. and meridians of longitude 42°30' and 46°30T. Yemen was known as “Arabia Felix” and had high civillization in ancient age. But since its hard natural environments, the development of this country fell behind the time. Among of them, water supply problem is the most important matter. In response to the request made by the Government of the Yemen Arab Republic, the preliminary survey of the “Rural Water Supply Projects were carried out by the Japan International Cooperation Agency (JICA). In this paper at first, we elucidate the background of water supply problems and the feature of geohydrological condition of this country. Next, we clarify the mode of occurrence and movement of groundwater which is restricted by the condition mentioned above. The summary of this paper is as follows : 1. Topographical feature. i. Yemen's main watershed runs from north to south and divides the country into two parts, western half and the eastern half. ii. The main watershed or central highland is comparatively flat and in some areas tectonic basins are pointed out. 2. Hydrological feature. i. As shown in Figure 7, the highest annual rainfall falls in the central highlands and the lowest in the eastern lowlands and the western lowlands. ii. Springs are observed in the wadi beds and support some small streams in the mountain area. 3. Hydrogeological feature. i. Geological succession is shown under. (lower to upper) Basement complex-Pre-Cambrian Wajid sandstone-Ordovician Kohlan series-Lower Jurassic Amran series-Upper Jurassic Tawilah group and Medj-Zir series--Cretaceous to Paleocene Yemen volcanics-Upper Cretaceous to Tertiary Baid formation-Miocene to Pliocene Quaternary basalts-Alluvium ii. Main aquifer in this country is Alluvium, Quaternary basalts and Yemen volcanics. On the other hand the rest can be regarded as aquitard or aquiclude, (especially basement complex as aquifuge). iii. As shown in Figure 12, aquifers are exposed in the central highlands and in the eastern and the western lowlands and aquitards or aquicludes are exposed in the mountain area. 4. Mode of occurrence and movement of groundwater. i. From mentioned above condition, the central highlands can be regarded as recharge area of groundwater. ii. For the most part, perennial streams in the mountain area are feeded by the outflow of groundwater from the central highlands. iii. In Tihama plain and the eastern lowlands alluvium underlies a thick cover of eolian deposits and for its high infiltration capacity, surface flow change into groundwater rapidly.
This study aims to discuss the method of land-type classification and ecological land evaluation especially for the landscape conservation in Izena Island located in Okinawa Islands, southwest Japan, wherein geographical distributions of plant communities (actual vegetation) were phytosociologically surveyed by the author et al. (1978). First of all methodological discussion concerning land classification, the concept of which has been reviewed by many applied geographers like MABBUTT (1968), was carried out. In this article the author proposed “potential natural vegetation (TÜXEN 1956) and landform” -oriented land classification as a sort of bio-physical land classification from genetically interpreted landscape approach. This method of classification is considered to be useful for land evaluation because of the integrated character of the two indexes and the appropriateness of forming a connection with land-use through actual vegetation which is influenced by both land potentiality and land use. In this study island land was classified into 13 bio-physical land units and their connection with other land elements such as surface geology and soils was considered. Such land units were mapped and connected with land use by using vegetational substitution. In the contemporary relationship possibility of land uses and land-use forms seem to be dependent upon the potentiality of land units. It is suggested that land evaluation can be performed through consideration of the way the relations between land units and land uses should be planned from the ecological point of view in the future. Concerning such ecological land evaluation, land units have summarized into 6 evaluated groups which present common characters for the countermeasures of land conservation. Then, in the specified area of the study island, land evaluation was tried for the purpose of protection of nature and recreation. This is an example of a landscape plan based on the results of land evaluation, which include the importance of land conservation, the value of natural or semi-natural vegetation and the desirability of land for the construction of roads, footpaths and recreational facilities. As a result of the case-study, the effectiveness of land classification and ecological land evaluation has been suggested. This study is a preliminary attempt to join the geographical and ecological method to landscape planning through land-type classification and evaluation. This sort of approach seems to get much importance under the critical circumstances for the development planning in Japan, especially in the humid subtropical islands where land potentiality for developments is relatively low and land itself is very limited.
Geoscientific papers on the Mineral Economics are reviewed and presented following 3 categories mentioned hereunder : 1) Geochemical study and discussion on the resources mainly based on the abundance of the elements in the earth-crust. 2) Geographical study on mineral production and reserve or resources such as area-mineral production relation and mineral production per square kilometer. 3) Geostatistic study forecasting cut-off grade, reserve, resource as well as future technical innovation. Limited number of geoscientific papers on the mineral economics lead the author to stress that more geoscientific contributions are needed to develop new horizon of geoscience as well as to forecast the mineral industries in the future.