Suitable areas for subirrigation and sprinkler irrigation were identified in Richelieu and St-Hyacinthe counties. / Land suitable for subirrigation includes uniform sandy textured profiles deeper than 1 m, with hydraulic conductivities greater than 0.5 m/d and lying on a clay layer at approximately 2 m from the surface, and with slopes less than 0.5% and little or no microrelief. / Soils that failed to satisfy the subirrigation criteria and that would most benefit from sprinkler irrigation were identified. These soils had available water holding capacities of less than 7.5 cm per 100 cm of soil. Most of the soils suitable for sprinkler irrigation were shallow sand (50 cm) over clay. / Both the Richelieu and St-Lawrence Rivers could meet the flow demand for the total irrigated area. However, 57% of the subirrigable land is located at more than 20 km from the Richelieu and St-Lawrence and could be more economically supplied by the Yamaska River. The Yamaska River could supply all the subirrigated land in its vicinity (4 900 ha) and part of the land suited for sprinkler irrigation (1 000 ha) 4 out of 5 years. (Abstract shortened by UMI.)

Mole drainage is an inexpensive form of drainage particularly suited to clay soils. / Mole drainage is approved by Le Conseil des Productions Vegetales du Quebec to drain clay soils with low hydraulic conductivity. A few known trials on this technique of drainage have been done in Ontario and Alberta. In England and New Zealand, this technique is widely used. The large surface of heavy clay soil cultivated in Abitibi-Temiscamingue makes this region an excellent choice for trying this technique. / Two sites established on two soil series (Palmarolle, Roquemaure) have been moled in Abitibi-Temiscamingue. These soils represent 21% of the cultivated land in this region. Twelve plots have been moled at varied depths, spaces and lengths. Physical and chemical soil properties have been measured to identify their influence on mole drainage stability. Water table, rainfall and the stability of the mole drains were monitored for three summers. Mole drain stability was observed with a borescope. Maturity growth and yield of a hay crop, and three types of cereals were measured. / The mole drainage technique is satisfactory in heavy clay. The organic matter (${>2 %}$), the water content of the soil (${>40 %}$) at moling time and a small amount of rainfall (${<6}$ mm) in the first week after moling positively influenced the stability of the mole drains. Some mole drains have kept 75% of their initial opening after three years of life. The water table was lower on one mole drained site. The yield of the hay and the three cereals were higher on the moled parcels. (Abstract shortened by UMI.)

Field water table measurements were taken at two sites in Southern Quebec in order to validate DRAINMOD, a field scale water table management model. Two growing seasons of data were collected on a loamy sand soil near Sorel, Quebec and one year of data on a clay soil to the south-west of Montreal. Several water table management schemes were investigated, ranging from conventional subsurface drainage to automated subsurface irrigation. / DRAINMOD was used to simulate the measured water table fluctuations and relative corn crop yields over the growing season. Verification of the model was needed to determine if it could be a useful tool in the design and operation of water table management systems for the Quebec region. / It was found that DRAINMOD output closely simulated the water table fluctuations for conventional drainage and subsurface irrigation plots provided no exceptional circumstances existed. More study is needed in some areas such as bedded fields and in the use of fluctuating water level control structures.

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