Author
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Lentz, Rodrick |
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Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 3/12/2003 Publication Date: 12/1/2003 Citation: Lentz, R.D. 2003. Inhibiting water infiltration with pam and surfactants: applications for irrigated agriculture. Journal of Soil and Water Conservation. 58(5):290-300. Interpretive Summary: Of the irrigation water diverted for irrigation in the US, about 17%, or 72,400 ac ft/day, is lost in conveyance to farmers' fields. Most of the loss is via seepage, and represents an average national revenue loss of $1.2 million/day. As much as 25% of water applied to furrow-irrigated fields can be lost from the rooting zone due to nonuniform water application, for an average national loss of $24 per irrigated ac. This study demonstrated that a relatively inexpensive anionic, water-soluble polyacrylamide (WSPAM), already used in irrigation to control erosion, can be used to inhibit water infiltration into soils. The research identified specific polymer application protocols that can reduce seepage losses and increase furrow irrigation application uniformity. This study also shows how anionic surfactants can be used for the same purpose. These treatments potentially can 1) decrease infiltration into unlined canals and reservoirs, 2) reduce infiltration at the inflow end of furrows, relative to outflow ends, thus improving application uniformity and reducing seepage losses, 3) conserve irrigation water, and 4) reduce irrigation costs. Technical Abstract: Efficiencies of surface irrigation systems are often limited by infiltration conditions. Treatments that decrease infiltration into unlined canals, reservoirs, and the inflow end of furrows relative to outflow ends would reduce seepage losses and improve application uniformity. Several laboratory studies evaluated effects of high molecular-weight (10-15 Mg/mol), water-soluble, anionic PAM, alone and combined with anionic surfactants, on the hydraulic conductivity (KSAT) of soils. Dry soils were treated with a one or two treatment solutions and subjected to conditions which simulated those in an irrigation furrow or pond. The KSAT of soil packed in columns was measured with a constant head apparatus for 19 h. PAM treatment concentrations > 125 mg/L applied to dry soils preceding flooding reduced KSAT by 25% and a 10-mg/L PAM + 29k-mg/L sodium-lauryl-sulfate surfactant application reduced KSAT by 70%, relative to controls. Miniflume tests then applied the treatments only to the inflow end of the "mini-furrows". The 125 and 250 mg/L PAM treatments significantly improved water application uniformity: cumulative infiltration was reduced in the upper half of miniflume furrows and increased in the lower, relative to controls. When applied to dry soils and allowed to dry over night, as may be done when treating irrigation ponds, the 1000 mg/L PAM solution reduced KSAT by 60 to > 90% in silt loam and clay loam soils. Either the single or combination treatments could potentially be used to increase the uniformity of furrow water applications and reduce seepage from unlined irrigation ponds and canals. |
