Evaluation of low-cost lining materials for field channels

Abstract

Seepage losses from field channels are too high, making surface irrigation the inefficient method of water application. The high cost of lining hindered the use of most of the common lining materials for lining field channels. With an objective of identifying and testing low cost lining materials for field channels, a study was conducted at K.C.A.E.T., Tavanur. Four low-cost materials were tested in the experiments. The physical property tests on different RHA-cement types showed that the waterpercentages required to attain standard consistency of the RHA-cements ranged between 58.33 to 58.53. The mean initial setting times observed were ranging from 55.67 min, for RHA-20, to 241.39 min., for RHA-40. The final setting times ranged between 397.74 and 600.36 min. The compressive strengths of the RHA-cement made mortars were determined after 3, 7, 14, and 28 days of curing. The two factor analyses of variance revealed that both the days of curing and RHA-cement types were sources of variation. RHA-20 mortars were significantly weaker than RHA-25 and RHA-30 mortars for 7 days of curing, and for 14 and 28 days of curing a significant difference in the compressive strengths ofRHA-20 and RHA-30 was observed. The average seepage rates were obtained as 3.536, 92.786, 356.278, 26.190 and 633.296 Vm2/day for plastic, RHA-30, Kaolinitic clay, Bentonite lined and the unlined channels respectively. The respective steady seepage rates from plastic, RHA-30, Kaolinitic clay, Bentonite lined and the unlined channels were 0.984, 72.283, 260.256, 12.530 and 433.886 Vm2/day. Plastic lining saved 99.774 per cent of the seepage as compared le. ti:,unlined. RHA-20, RHA.:.25, and RHA-40 linings respectively were having steady seepage rates of 150.917,11.959, 101.161 lIm2/day and saved 65.377, 74.315, and 76.792 of the seepage against the control.The RHA-30 lined surface was the smoothest with a roughness coefficient of 0.01853, the same were 0.0236, 0.0255, 0.02497 and 0.0238 respectively for plastic, Kaolinitic clay, Bentonite and unlined surfaces. The total number of weeds grown on plastic, RHA-30, Kaolinitic clay, Bentonite and unlined surfaces respectively were 294, 7, 287, 163,and 547. The initial costs of constructing I Km length of field channel were obtained as Rs.54657.86, 83008.84, 68062.50, 81490.31 and 21000.00 for plastic, RHA-30, Kaolinitic clay, Bentonite and unlined channels respectively. The actual cost required to construct the five 10 m channels with plastic, RHA-30, Kaolinitic clay, Bentonite linings and with out lining respectively were Rs. 548.40, 832.15, 618.45, 1330.08 and 210.00. From the overall compansons of water tightness" surface roughness, weed controlling ability, structural stability, durability and cost RHA-30 lining was found to be the best among the tested lining materials. A combination type lining using plastic and RHA-cement as a cover will probably be an ideal lining, as each can complement the shortcomings of the other.