Investigating Alternative Methods for Reducing Seepage Loss from Earthen Ponds

Master's Thesis from the year 2005 in the subject Engineering - Geotechnology, Haramaya University (Faculty of Agriculture, Department of Agricultural Engineering), language: English, abstract: Water harvesting technologies are being promoted at the household level in Oromia Region. Among the different types of surface runoff water harvesting structures adopted in the region, earthen pond seems to be the major one practiced by many farmers. Huge numbers of earthen ponds have been implemented to date in different sites. However, the problem of seepage is not adequately addressed; loss of water from the ponds due to seepage and evaporation has been reducing the performance of the ponds. These days, polyethylene membrane has been provided by the government to solve the problem and this membrane has been found to reduce seepage loss by 90%. Unfortunately, the membrane is too costly and not easily available to all farmers.

Therefore, to alleviate the situation, alternative methods of reducing seepage loss were investigated in this experiment. Biological and physical methods for reducing seepage were evaluated in small ponds constructed in permeable silty clay soils of the Region. The biological method involved use of bio-plastic sandwiches made up of successive layers of soil, manure, vegetative material and soil. The physical method involved compacting of existing soil and treating the surface by termite mold mix soil. The biological methods reduced the mean cumulative seepage rate by 47% and the physical treatment reduced by 21% after 90 days of wetting compared to the untreated soil. Therefore, both methods can be cost effectively applied by the farmers.