Dabus Irrigation Development Hydrogeology Study
Executive Summary
The hydrogeological study assessed groundwater conditions in the Dabus Irrigation Project area to:
- Predict groundwater level rise from irrigation
- Evaluate water quality changes
- Determine drainage requirements
- Assess groundwater potential for water supply
Key findings:
- Area underlain by Precambrian basement rocks (granite, granodiorite) with some meta-sediments
- Groundwater depth varies from 4-7m in plains to 10-15m in elevated areas
- Water quality is fresh and meets standards for domestic and irrigation use
- Estimated groundwater rise of 0.2-0.5m/year in vulnerable areas near river
- Surface drainage recommended to prevent waterlogging
- 4 piezometer wells and geophysical surveys recommended for further study
Key Sections
1. Introduction
The study area covers 10,000ha along the Dabus River with tropical climate (680-1200mm annual rainfall).
2. Methodology
Combined office studies, field investigations, water sampling, and data analysis.
8. Geology
Dominantly Precambrian basement rocks with some Quaternary alluvial deposits near the river.
9. Hydrogeology
Groundwater occurs in weathered/fractured basement and alluvial deposits. Recharge mainly from rainfall.
12. Water Quality
All samples show low salinity (EC 70-390 μS/cm) and are Ca-Mg-HCO3 type, suitable for irrigation.
13. Groundwater Rise
Estimated 0.2-0.5m/year rise from irrigation, with highest risk in flat areas near the river.
16. Recommendations
- Install 4 piezometer wells (50m depth)
- Conduct geophysical surveys (10-15 VES points)
- Implement surface drainage systems
- Monitor groundwater levels and quality
Key Tables and Figures
- Table 13.1-13.3: Canal seepage losses and groundwater rise estimates
- Figure 8.1: Hydrogeological map
- Figure 12.1: Piper diagram of water chemistry
- Figure 13.1: Groundwater flow conceptual model
Conclusion
The study found minimal waterlogging risk for most of the irrigation area, with localized risk near the Dabus River. Proper surface drainage and monitoring are recommended to manage groundwater levels. Water quality is suitable for both irrigation and domestic use.