Summary of the Gambela Plain Master Plan Survey Document
This document outlines the updated working programs for survey work related to the Master Plan of Utilization of Land and Water Resources of the Gambela Plain. The surveys were conducted by Soviet specialists and cover various aspects including topographic, geological, soil, vegetation, and hydrological studies.
1. Introduction
The working programs were updated based on additional studies of natural conditions conducted after the initial program was compiled. The surveys cover:
- Engineering-geodetic and topographic work
- Engineering-geological and hydrogeological work
- Soil-reclamation survey
- Geobotanic survey
- Hydrological and meteorological survey
2. Key Survey Components
Engineering-Geodetic and Topographic Work
Updated topographic surveys were conducted at various scales (1:10000, 1:5000, 1:2000) with adjustments made based on accessibility and available materials. Helicopters were used for inaccessible areas.
| Work Description | Original Volume | Updated Volume |
|---|---|---|
| Topographic survey at 1:10000 scale | 150 km² | 70 km² |
| Survey at 1:5000 scale | 75 km² | 17 km² (field work) |
| Survey at 1:2000 scale | 4 km² | 2 km² |
Engineering-Geological and Hydrogeological Work
Drilling volumes were reduced from 22,582 running meters to 8,000 running meters due to inaccessible areas. Geophysical methods like vertical electric sounding were added at 1,700 points.
Soil-Reclamation Survey
Traditional survey methods proved impractical due to inaccessibility. Alternative methods were employed:
- Route method: Used in accessible areas with interpretation of aerial photos
- Microkey method: Used with helicopters in inaccessible areas
Soil pits were reduced from 3,450 to 550 due to these methodological changes.
Geobotanic Survey
Vegetation surveys at 1:200,000 scale covered 23,000 km² using similar route and microkey methods as soil surveys. Two standard plots (4,400 ha total) were established for detailed land clearing studies.
Hydrological and Meteorological Survey
The program included:
- Reconnaissance of major rivers (Baro, Birbir, Sor, Geba, etc.)
- Water discharge measurements at multiple gauge stations
- Suspended load measurements
- River depth soundings
- Meteorological observations at 3 stations
- Water and sediment sampling for analysis
3. Challenges and Adaptations
The survey faced significant challenges due to the inaccessibility of much of the Gambela Plain, requiring:
- Extensive use of helicopters for transport
- Adaptation of survey methods (microkey approach)
- Reduction in some field work volumes with increased office-based interpretation
- Reliance on aerial photography and geophysical methods where ground access was impossible
4. Conclusion
The updated survey programs successfully adapted to the challenging conditions of the Gambela Plain, utilizing innovative methods to gather necessary data while reducing costs and time requirements. The collected information provides a comprehensive basis for the Master Plan of land and water resource utilization in the region.