| Popis: |
Irrigation water supplies are becoming limited, and there is a need to extend the usefulness of current water resources. Previous laboratory studies demonstrated that certain water-soluble polyacrylamide solution (WSPAM) and cross-linked PAM granule (XPAM) treatments effectively reduced infiltration into soils. We evaluated the efficacy of these treatments for reducing water seepage losses in an unlined irrigation reservoir. Five treatments were applied to plots on the lower side slopes of a reservoir basin before it was filled in April 2001: controls; 0.016 kg m -2 WSPAM (1000 mg L -1 solution); 0.2 kg m -2 XPAM + 0.13 kg m -2 NaCl; 0.4 kg m -2 XPAM + 0.13 kg m -2 NaCl; and 0.8 kg m -2 XPAM only. Ring-cylinder seepage meters installed in each experimental plot were used to monitored seepage rates from May through October in 2001 and 2002, without further treatment applications. The WSPAM and XPAM treatments were equally effective for reducing pond seepage in 2002 but not 2001. On average, they reduced mean seepage rates an average 50% relative to the 22.4 mm h -1 control value and prevented the loss of 19.7 m of water through the seepage rings over the two irrigation seasons. The 0.016 kg m -2 WSPAM and 0.2 kg m -2 XPAM + 0.13 kg m -2 NaCl treatments are most cost effective, but the greater XPAM rates appeared to be the most durable treatments, since they retained their efficacy through the end of the second irrigation season. Results are consistent with a previous study suggesting that adding NaCl to XPAM treatments reduced required XPAM inputs without reducing treatment efficacy. The WSPAM and XPAM treatments provide several effective options for reducing seepage losses in earthen reservoirs. |
