Permeability das'nt relate to total porosity, but relate to effective porosity except the pores in the clay content.
In order to calculate effective porosity it is expected that techniques of cross-plot analysis which has been used for consolidated or semi-consolidated reservoir in oil industry are applied to unconsolidated aquifer. Each logging of density (ρ _b), gamma-ray (γ _ray), normal resistivity(R), and spontaneous potential (SP) is very often carried out in water well on the point of economic view, however we see the difficlties of doing cross-plot analysis because conceptive interrelation among their logs is obscurity. Then, we expand a mathematical treatment concernig cross-ploting between density and neutron (φ _N) logs which was developed by J. A. Krug and D. O. Cox in 1976, in the range of unconsolidated formation.
Consequently, we get as the following matters: the quantitative detail of effective porosity and the clay content on circumference of aquifer; and the accuracy of the values which are presumed in a mathematical tretment process.
Therefore, some cross-plot among each water-well logging (ρ _b, γ _ray, R, and SP) will be able to analyze in fulure by combining the interrelation in the variables obtained from analysis of ρ _b-φ _N cross-plot.

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The writer has engaged in hydrogeological survey and technical services for ETHI-OPIA A. I. D. BANK Undeground Water Resources Development Project.
This project was started on Novemder 1974, ultilizing six Japanese drilling rigs (four percussion type and two rotary type) for the purpose of solving the drought problem.
Based on the data odtained from this project the writer classifies the ground water types into five classes, and are listed as follows:
1. Abyssinia plateau type
2. Rift valley type
3. Dire Dawa fan type
4. Ogaden desert type
5. Awash valley type
The discharge rate is expected 100-300 1/min. with drawdown 10-40m, except the Ogaden desert in which the successful drilling depth are from 50m upto 120m.
Most of the water in the survey area has a conductivity around 500ppm with hith hardness. In the Ogaden area, water from the wells shows high chlorine contents of 2000ppm and up.
The water of some wells in the Rift valley, contains as high as 6ppm Fluorine.
In the Awash valley the water of the wells shows high water temperature of above 30°C.
As for the drilling method, rotary drilling method, with the exception of few wells by air rotary drilling method, was used in the Abyssinia platau. Cable tool method was used in the Rift valley area. Either cable tool or rotary method was used in the other areas.

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Groundwater survey, on the Nakagawa River delta, was carried out by the Agricultural Administration Bureau of Chugoku-Shikoku, in 1971.
The well, which was pumped for the test, is 150 meter deep, and has a 15 centimeter casing perforated from 50 to 60 meters.
As determined by the Theis nonequilibrium formula, the results are as follows: The coefficient of transmissibility (T) is 7.8 x 10^-4square centimeter per second, the coefficicient of storage (S) is 2.2 ×10^-5; the coefficient of permeability (K) is 1.31×10^-4meter per second; the specific capacity (q) is 0.0094 cubic meter per second; and the influence area (R) is 148 meter.

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