REDUCING WATER SEEPAGE FROM EARTHEN PONDS

Small earthen reservoirs have proved to be a promising answer to the p roblem of storing water on arid-land farms. However, these little pond s or tanks can lose very large amounts of water through seepage. To re duce such losses is a vital need. In the present experiments, chemical , physical, and biological methods for reducing seepage were evaluated in small ponds created in a permeable, calcareous, silt-loam soil. Th e chemical method involved treating the top 10 cm of soil with sodium carbonate (Na2CO3). The physical method involved compacting the soil. And the biological method (the so-called ''bio-plastic sandwich'') con sisted of successive layers of soil, manure, vegetative material and s oil. The chemical treatment proved less efficient than the other two. Compared to the untreated soil, the physical and biological methods re duced the mean cumulative seepage rates (measured 350 days after the i nitial wetting) by 72% and 67%, respectively. Both of these treatments seem to be cost-effective and ready to be applied to the farm ponds o f Pakistan.