The first part of two-series paper deals with the groundwater resources and uses in Australia, and the organization of the groundwater studies.
Groundwater in Australia occurs in surficial aquifers which cover 25 percent of the continent, and in the underlying sedimentary basins which cover about 65 percent and fractured rock provinces about 35 percent. Groundwater abstraction from the aquifers is roughly in the proportions: surficial aquifers,60 percent; deeper aquifers in sedimentary basins,30 percent; and fractured rock aquifers,10 percent.
The total potential yield of groundwater is about 70×10⁹m³ per year. The total groundwater withdrawal is about 2.5×10⁹m³ per year, equivalent to about 14 percent of the total amount of water used in Australia, from about 500,000 bores. About 60 percent of Australia is totally depend on groundwater, and in another 20 percent of the country more groundwater than surface water is used.
The organization of the groundwater studies in Australia divides into three types which are Commonwealth Government Laboratories, Universities and State Government Organization. Two hundred staffs research the hydrology in the Division of Water Resources, Commonwealth Scientific and Industrial Research Organization (CSIRO). Water Authority in each state has the responsibility for planning and managing water resources and water services. They have done joint studies on groundwater with CSIRO and Universities.

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The second part of two-series paper deals with each groundwater problem in Australia. The studies on salinity, clearing land, groundwater recharge and Great Artesian Basin are discussed.
The salinity problem divides into two types which are the natural salinity and the salinity by human activities. The salinity problems and examples of the measurement in Moora, Western Australia and in River Murray, South Australia are reported.
Another feature of the groundwater study in Australia is to quantify the changes in the input and output of salt and water when land use changed from forest to agriculture. The study in Collie, Western Australia after clearing has been shown and the hydraulic and hydrological equilibriums have been discussed.
Significant contributions to the theory of unsaturated movement of water downward from the ground surface have been made in Australia. The estimation of recharge rates using tracer techniques has been developed. It is clarified from the recharge project by CSIRO in perth that the recharge rate not only depends on a kind of vegitations but also on a density and maturity of the stems. The management of land use after understanding the water balance is necessary.
The recent studies of the Great Artesian Basin which is a multi-layered, confined groundwater system occupying 20% of the area of Australia, have been introduced. The features of Great Artesian Basin research have been the systematic application of isotope techniques.

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Muika-machi basin is located on middle river basin of Uono river. On this area, great amount of snow fall in winter. Inhabitants (about 50 thousands population) sprinkle groundwater for melting snow on the road and roofs. Some damage has been done to the area as a result of lowering of hydraulic head. The author investigated distribution of location of aquifers, permeability coefficient, pumping volume of groundwater, hydraulic head, etc. to clarify the groundwater flow system on this area. The summary of the results is shown below. (1) In Muika-machi town which is located on the center of Muika-machi basin, confined aquifers are ten-odd meter deep, about 10 meter thick (the AG layer) and about 30 meters deep,50-60 meters thick (the BG1 layer). These aquifers show good continuity. The BG1 layer continues to unconfined aquifer on the suburbs of Muika-machi. (2) The pumping volume in a snowfall season is 76% of the volume in a year (48 million m3). The pumping volume from the BG1 layer is94% of the all. (3) In a non-snowfall season, groundwater which is pumped up in Muika-machi town is mainly supplied from the direction of the upstream of Uono river. In snowfall season, pumping volume of Muika-machi town increase largely. Then groundwater which is supplied from the direction of the upstream of Uono river to the BG1 layer increase a few times. But the amount of increase from this direction is insufficiency. Through examinations it is considerd that this shortage is supplied by a large amount of leakage from the AG layer.

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The land subsidence at Muika-machi and its outskirts was analized by a quasi threedimensional model using finete element method. Parameters were decided by geological data, hydraulic data, pumping volume of groundwater, etc. These data were investigated at the site in detail. Calcutated values of hydraulic head and the amount of land subsidence were in good agreement with measured values. An estimation of future subsidence by this model showed that the zone of the large amount of land subsidence will spread over the whole town. This distribution is quite unlike the conventional pattern which showed that maximum subsidence was located in the northern extremity of this town. This change is caused by the latest increase in wells at the center of this town.

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[in Japanese]

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[in Japanese]

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