Previous concepts for groundwater yield have been studied to define its proper scope and purpose of utilization. A total of nine terms were identified by the review. They are two types of optimal yield, appropriate utilizable yield, optimal critical discharge, safe yield, perennial yield, sustained yield, mining yield and permissible yield. These terms are categorized into five groups of 1) critical pumpage capacity for individual well, 2) appropriate utilizable quantity for multiple wells, 3) withdrawable amount for groundwater use from a basin, 4) extractable yield on nonrenewable groundwater basin and 5) permissible level in groundwater development and preservation. Moreover, in order to evaluate the characteristics of each term, a total of four parameters, namely area, economic aspect, harmonious of water balance and socio economic (environmental scientific) aspect were examined. As a result, the concept of permissible yield is ascertained as the only one term that satisfies all the parameters. The precise definitions of each concept of groundwater yield were given by this study. Under the proper use of these definitions, determination of groundwater yield in accordance with the plan could be made, which would be helpful for the formulation of groundwater development plan, especially in the developing countries where the groundwater is extensively utilized.

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Four rows of the longshore bar (Ist-bar to 4th-bar) were emerged during the maximum shortage water at the Shingai-hama coast in Lake Biwa, central Japan on 15 September 1994. The lake water level recorded -123cm from the average without precedent during the recent time. Based on the facies analysis of the 4th-bar deposit exposing at the most offshore side, it can be classified into the five sedimentary units of A, B, C, D and E, and each unit is bounded by the erosional surface of b, c, d, e and f. The individual unit is characterized by offshore lateral accretion (progradation), but the berm crest deposits indicate also vertical accretion (agradation) as stepping upto the higher topographic position. The 4th bar deposits were formed mainly by swash waves during storm weather. The unit B overlies on the unit A vertically and offshoreward. The boundary b between unit A and B is erosional surface, and can be interpreted as a reactivation surface. After the formation of the boundary, the prominent wind built another sedimentary units from B to E of the 4th-bar deposit. Facies analysis of the 3rd-bar deposit indicates the features of onshore lateral accretion which can be interpreted as ridge and runnel. These evidences show the different forming processes between the 3rd- and 4th-bar deposits.

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Six units of sedimentary complexes are discriminated in the Tsujido area, west of Omine Range, namely the Daifugendake, Wasabidani, Takahara, Obadanigawa, Ui and Akataki Formations in structurally desending order. The first three units belong to the Chichibu Terrane, while the rest belongs to the Shimanto Terrane. All the units are stacked up to form a low-angle piled nappe structure showing generally downward-younging polarity from the Daifugendake Formation to the Akataki Formation except for the Ui Formation. The sole thrusts of the Akataki and Obadanigawa Formations may be regarded as out-of-sequence thrusts. The nappe structure is modified by later high-angled faulting such as the E-W trending Shimotakogawa Fault and the N-S trending Kitozumi Fault which were newly recognized here. The Daifugendake Formation (Upper Jurassic) is composed of chert-clastic sequences. The Wasabidani Formation (Upper Jurassic melange) is characterized by containing huge blocks of limestone, greenstones and chert. The Takahara Formation (lower to middle of Lower Cretaceous) is a melange containing blocks of chert, limestone and greenstones. The Obadanigawa Formation (Albian〜Cenomanian) consists mainly of sandstone-rich clastic sequences. The Ui Formation is newly introduced here, and is characterized by repetition of sandstone-rich clastic sequences (mainly Cenomanian) and melange facies (Turonian〜Santonian). The Akataki Formation (Coniacian〜Campanian?) is composed of a melange with blocks of red chert, red mudstone and greenstones. It has been well-known that the Chichibu Terrane is missing in the central part of the Kii Mountains. Our research has revealed that the Obadanigawa Formation which occupies the uppermost part of the Shimanto Terrane structurally is also missing in the same area.

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The Pliocene widespread tephra in central Japan is newly detected. It is distributed in Japan Sea coast area as the Itayama-Nym ash layer in Niigata region and the YT3 ash layer in Toyama region. It is also found in the Pacific Ocean side as the Souri ash layer around Ise Bay. The thickness of each layer ranges from 20cm to 15m. These ash layers occur as sediment-gravity flow deposits in subaqueous environments, accompaning fallout deposits. These ashes mainly consist of glass shards. Chemical composition of glass shards is almost coincident, and characterized as SiO_2 is 80-81%, FeO is 0.9-1.3% and CaO is 0.47-0.60% on water-free basis. In heavy mineral associaion, biotite and hornblende are predominant, accompaning variable minerals such as allanite, orthopyroxene, oxyhornblende, clinopyroxene, zircon, garnet, muscovite and apatite. The source volcano can be assumed at northern Gifu Prefecture, and these deposit represents one of the intensive Pliocene volcanic eruptions in central Japan.

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Pliocene Bando 1 Volcanic Ash Bed is intercalated in the fluvio-lacustrine Tokai Group in central Japan. The depositional processes of this ash bed is clarified based on facies analysis. Five sedimentary facies are recognized, indicating pyroclastic fall and reworked (mudflow, flood flow, channel fill, and swamp or back swamp) deposits. According to the successions of volcaniclastic sedimentary facies, deposition of this ash bed can be divided into 4 stages which relate to volcanic eruptive activity. Stages I and II are the eruption stages, during which fallout volcanic dust and ash covered over all this study area (the northern Mie Prefecture). Mud flow stage in Stage III is characterized by the first appearance of cm-order pumice grains. During Stage IV, volcaniclastics were deposited in the fluvial systems. Depositional mechanisms of poorly sorted trough cross stratification, autofluidization, and hyperconcentrated (flood) flow deposits are discussed based on grain-size distribution, grain shape, grain settling velocity, and facies successions. Trough cross stratified ash with many pebble- to cobblesized pumice grains can be explained by the peculiar grain settling velocity formula which indicated more varied grains in diameter can be deposited under a small range of settling velocity, comparing with the spherical particles. Autofluidized flow deposits is recognized as the dish structured deposits. Autofluidization is quantitatively supported by the combination of superficial fluid velocity at minimum fluidization, and superficial fluid escape velocity from the liquefied part. Hyperconcentrated (flood) flow is rheologically characterized as the flow between mudflow and fluidized flow. This flow can be considered as en masse fashion, not grain-by-grain fashion.

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