Water Conveyance Loss and Designing Conveyance System - Practices of Irrigation and On-farm Water Management - page 8

1.1.6 Reduction of Seepage
Lining is the straightforward way to reduce seepage from the channel. Besides the
channel, sometimes the earthen reservoirs are faced with the problem of seepage. A
variety of techniques are available to control seepage from the earthen reservoir or
ponds. These include physical, chemical, and biological methods.
1.1.6.1 Physical Method
In this method, the bottom and sides of the ponds are soaked with water until
their moisture contents are close to field capacity. Then the soil is physically com-
pacted. Compaction can be done with either manual or tractor-mounted compactors.
Walking cattle or buffaloes over the area will help. The amount of compaction
achieved depends on the load applied and the wetness of the soil. The soil's physical
and chemical properties are also important. The level of compaction can be assessed
by measuring the soil bulk density or by the force exhibited by the Penetrometer to
enter the soil.
1.1.6.2 Chemical Method
Certain sodium salts such as sodium chloride, tetrasodium pyrophosphate, sodium
hexametaphosphate, and sodium carbonate can reduce seepage in earthen ponds.
Among them, sodium carbonate performed better (Reginato et al., 1973 ) . Sodium
ions cause clay to swell and clay particles to disperse and thereby reduce or plug
water-conducting pores in the soil. Seepage losses can be reduced by mixing sodium
carbonate with locally available soil and applying the mixture by sedimentation.
The recommended rate is 2.5 t/ha, into the top 10 cm soil. The sodic soil, which is
naturally high in sodium salts, also do the job.
1.1.6.3 Biological Method
“Bio-plastic,” a sandwich made up of successive layers of soil, manure (from pigs,
cattle, or others), vegetable materials, and soil can reduce percolation loss. This
creates an underground barrier to seepage. Kale et al. ( 1986 ) obtained a seepage
reduction of approximately 9% by using a mixture of cow dung, paddy husk, and
soil.
1.1.7 Lining for Reducing Seepage Loss
1.1.7.1 Benefits of Lining
(i) savings of water
(ii) reduced canal dimensions and right of way - cost
(iii) reduced water logging in some cases