Description and evaluation of zigzag furrow irrigation in the inter-Andean Valleys of Bolivia

Surface irrigation is the main irrigation system used in the inter-Andean valleys of Bolivia. However, the region's steep terrain precludes the use of conventional surface irrigation methods. Zigzag corrugated furrows, the most widely used irrigation method in the region, have proved suitable for the local conditions and are environmentally sound as they substantially reduce soil loss from water erosion. Satisfactory water management, however, appears to be lacking so our paper aims to study water use and suggest improvements. The experimental field work was carried out in Cebollullo, a rural community 2,780 m above sea level located southeast of the city of La Paz. The characteristics of the furrows vary with crop type and soil (class and slope). Lettuce crops grown in an experimental 566-m² plot with an average slope of 16.46% were studied. The plot was irrigated a total of 21 times at 2-3 days intervals and the effects of 10 of the irrigation events were evaluated taking weekly measurements during each event. Advance curves were constructed from data obtained at 16 measurement points. Advance and recession times, as well as inflow and outflow rates were determined on the basis of measurements made a 5-min intervals. Inflow rates at some measurement points were found to vary widely due to the indiscriminate use of water by farmers upstream of the experimental plot. Advance curves were found to be linear rather than potential or exponential as is usually the case with this type of irrigation system. Also, advance and recession curves were virtually parallel, which indicates uniform infiltrated volumes along the furrows. The average water application efficiency, surface runoff, and deep percolation loss for the 10 irrigation events examined were 17.47, 68.36, and 14.17%, respectively. Based on these results, the zigzag furrow irrigation system in the area investigated in the research reported in this paper would appear to be badly managed and implemented.