ARS | Publication request: PAM in irrigated agriculture: Processes and soil-PAM interactions influencing canal sealing

Submitted to: PAM and Alternatives to PAM
Publication Type: Proceedings/Symposium
Publication Acceptance Date: April 3, 2008
Publication Date: N/A

Technical Abstract: To identify or develop alternative polymers, which may successfully replace PAM as an irrigation reservoir or canal sealant, it is important to understand the nature of the sealing processes in these unlined, earthen irrigation structures and how PAM interacts with those processes to alter water seepage. Sediment and organic particulate loads in irrigation water can act via several sealing mechanisms to inhibit seepage losses from earthen canal inverts and wetted perimeters of storage reservoirs. The progression of native sealing in these earthen structures is opposed by any process that scours sediment previously deposited on the canal or reservoir wetted perimeter, attacks the thin depositional layer that has formed over an infiltrating surface, perforates the infiltration-inhibiting layer created near the soil surface, or alters the size and distribution soil macropores. These processes can expose deeper soil strata whose unaltered pore structure permits increased water infiltration. PAM may enhance or interfere with these processes through its effects on flocculation and settling of suspended particles, stabilization of soil aggregates, maintenance of pore integrity, and altering water flow characteristics (viscosity effects). The impact of PAM applications on seepage losses from earthen conveyances and reservoirs is a sometimes a complex function of stream channel and flow characteristics, type and amount of suspended sediment, amount and methodology of PAM application, and other factors. However, PAM applications can substantially reduce seepage losses and be a cost effective solution, particularly when water supplies are limited.