Mechanisms and Control of Percolation Losses in Irrigated Puddled Rice Fields

Abstract

The low water use efficiency of irrigated lowland rice is partly due to water loss by percolation. Mechanisms of percolation losses were studied in a puddled rice field with a permeable subsoil using simulation models and field experiments. Inclusion of small nonpuddled areas (1.5 m2 per 100 m2 of puddled soil) within the field with 5‐cm ponding water depth (PWD) increased field water loss from 2.7 mm d−1 to 15 mm d−1. Under‐bund percolation rate (lateral movement of ponded water into the bunds, then vertically down to the water table) was about 10 mm d−1 in a 25 by 100 m field. A one‐dimensional mechanistic soil‐water balance model, SAWAH, accurately simulated the measured water losses in a homogeneously puddled rice field only when lateral flow toward nonpuddled spots and bunds was prevented. Maintaining shallow PWD did not significantly affect percolation loss through uniformly puddled soil but greatly reduced losses in nonpuddled spots and under‐bund percolation. Sealing the bund walls with puddled soil material will decrease the horizontal conductivity of the bunds and may further reduce under‐bund percolation.

Estimating Percolation and Lateral Water Flow on Sloping Land in Rainfed Lowland Rice Ecosystem

“…Mean values indicate that Chum Phae, Surin and Ubon Ratchathani had net Tuong et al, (1994) also reported a high value of the lateral water outfl ow. They indicated that this high fl ow was due to the under-bund percolation.…”

More Rice, Less Water—Integrated Approaches for Increasing Water Productivity in Irrigated Rice-Based Systems in Asia

“…This outfl ow can be reduced by decreasing the rate of fl ow or by reducing the duration that fi elds are fl ooded. Technologies that reduce the rate of outfl ow can broadly be classifi ed into (i) soil management practices to increase resistance to water fl ow and (ii) water management practices to reduce the hydrostatic pressure (Tuong et al, 1994). a.…”

“…a. Soil management to increase resistance to water fl ow Puddling increases the hydraulic resistance of the plow sole that impedes vertical water movement during the crop growth period (Tuong et al, 1994). The effi cacy of puddling in reducing percolation depends greatly on soil properties.…”

Water Saving in Rice-Wheat Systems

“…"Rice environmental policy" is defi ned and implemented by the irrigation companies as part of their overall Land and Water Management Plans. There is considerable variation in percolation rates across soil types and within fi elds (van der Lely and Talsma 1978;Beecher et al, 2002) and small highly permeable areas can make a large impact on total percolation losses (Tuong et al, 1994;Humphreys et al, 1998). Therefore there has been widespread adoption of recently developed electromagnetic (EM31) survey technology for rapidly, accurately and inexpensively identifying soil variability and assessing suitability from texture, or more accurately from soil sodicity, for rice fi elds, irrigation channels, drains and water storages (Beecher et al, 2002).…”