VEGETATION CHANGE ON THE TARATA ALLUVIAL FAN: THE IMPACTS OF IRRIGATION TECHNOLOGY IN THE ANDEAN HIGHLANDS OF BOLIVIA
Open Access
- Author:
- Moats, Brentley Wade
- Graduate Program:
- Geography
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- None
- Committee Members:
- Karl Stephen Zimmerer, Thesis Advisor/Co-Advisor
Karl Stephen Zimmerer, Thesis Advisor/Co-Advisor - Keywords:
- Agriculture
Woody Vegetation
Irrigation
Remote Sensing
Watershed
Alluvial Fan - Abstract:
- Semi-arid woodland environments of the Bolivian Andes are a global center of biodiversity and integral parts of an agricultural landscape. Farmers traditionally relied on spate irrigation; however, a transition to canal-based irrigation began in the early 1990s with the construction of the Laka Laka Dam. While the goal was to create a system for year-round access and increase water use efficiency, the effects of the Laka Laka Dam project on woody vegetation have not been researched. The main pattern (>50%) of forest cover consists of ribbon-like strands along water sources, specifically the new concrete-lined canals. This study will assess the changes in woody vegetation cover along the irrigation canals, and the main flood channel, through a combination of remote sensing and field techniques. The spatial extents and temporal changes of this woody vegetation are explored by the comparison of pre-dam aerial photography (1990) with post-dam Quickbird satellite imagery (2006). Canals that remained earthen gained an average of 2% in woody vegetation from 1990 to 2006. Concrete-lined canals lost vegetation (13%) close to the center-line of the canal, but gained vegetation (5%) at distances of up to 20 meters from the canal. The main channel experienced an increase of 131% in woody vegetation between 1990 and 2006. Overall, the Taratan alluvial fan experienced a small gain in woody vegetation. Reasons behind this result are varied, but a large factor is the increase of irrigation efficiency and the total volume of water being applied to the soil for the purpose of agriculture. In effect, the irrigation water applied to the fields more than compensated for the restriction of soil moisture due to the canals’ concrete lining.