エチオピアの地下水

エチオピア農工業開発銀行(A.I.D.Bank)地下水開発プロジエクトにおける地下水開発について

抄録

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.