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The world population today is about 6.5 billion, and it is estimated that it will increase to 9.1 billion by the year 2050 (UN, 2004). It is estimated that irrigation consumes more than 80% of the good quality water. Due to the reduction in available water resources, the application of water-saving strategies, such as deficit irrigation and the use of underground water resources, can reduce water usage for irrigation. One strategy for the source control is to restrict the outflow in field drains such that the height of the water table is maintained at a shallow depth that allows certain crops to utilize groundwater to satisfy a portion of their water requirements. Shallow groundwater can be a significant source of water for agricultural production, especially during the drought period. The fraction of the crop water demand that can be met by shallow water tables depends on the crop grown, irrigation and drainage management, the soil type, the depth to the water table, and the shallow groundwater salinity(Ayars et al. 2006). A wide range of crops has been successfully grown that obtained a significant portion of the crop water requirement from shallow groundwater. The types of crops range from truck crops (pepper and carrots) to grain, hay, and some tree crops (e.g. date palm) that have salt tolerances from sensitive (lettuce) to tolerant (cotton). Although such observations have been made for moderately salt-tolerant perennial crops, such as alfalfa hay, vine and tree crops have a larger potential for in- situ water use from shallow groundwater than do annual crops because of their well-developed and established root system after the first growing season. Hutmacher et al. (1996) showed that cotton (Gossypium hirsutum L.) crops can obtain 20 to 50% of their water requirement from shallow groundwater under the proper irrigation management. The timing and amounts of surface irrigation impact the extent to which crops will utilize shallow groundwater. Judicious use of deficit irrigation in combination with shallow groundwater management is necessary to achieve optimal results (Ayars et al., 1999).

he objective of the study was to develop the water management operational plan at tertiary blocks for the growth of rice and corn. Study was conducted at reclaimed tidal lowland area which was located at Primer 10, Delta Saleh. This area was classified as a C-typhology land (dry). The methods of the study were survey, field measurements, computer simulation, and field action research. Study stages were consisted of survey and monitoring, water status evaluation, water management scenarios design, model simulation, and model adaptation. Computer model of DRAINMOD had been used to estimate the water table status and to design water table control operation at tertiary blocks. Simulation results showed that the model worked properly which was indicated by root mean square error of 1.45 cm, model efficiency of 0.97, and correlation coefficient of 0.84. Model adaptation for dry land condition (C-typhology) showed that the best scenario was land utilization pattern of rice-corn. This paper presented monthly water management operational plan for rice crop in first cropping season (CS1) during November-February period and for corn crop in second cropping season (CS2) during May-August period. Results of computer simulation and field study showed that the main objective of water management in this area was water retention in combination with land leaching.

Since the Middle Ages the Dutch have reclaimed many lakes and parts of the sea, creating polders. Drainage is required to use the land: for the inhabitants, for agriculture and for nature. Traditionally drainage was by gravity: through open (and later pipe) drains excess rainfall was transferred into open collector drains, from where the water was pumped out to a river, lake or the sea. Since the 1950s, land use has been changing towards a more diverse and intensive agriculture, more attention for nature, recreation and continuing urbanization. On top of this, the climate is changing: significant increases in precipitation, both average and extreme. Until recently, the solution to more excess water was to increase pump capacity. Yet the combined problems of climate change, sea level rise, subsidence and urbanization require more structural changes in water management. Drainage systems have to be modified to enable the shift from a strategy of rapid removal of all excess water to one that continuously controls water levels individually in each agricultural plot. A new approach of ‘retention, storage and controlled removal’ is being used to develop climate adaptation scenarios for the three hydro-ecological zones in the Netherlands, i.e.: (1) the man-made polder areas with marine clay soils along the North Sea coast and the former Zuider Sea; (2) the low-lying peat lands in the west and north; and (3) the sandy and loamy soils areas in the centre, south and east. New approaches for tailor-made drainage solutions following this strategy are being tested in various pilot areas in the three zones. Although the research is still ongoing, this paper presents the lessons learned to date related to the challenges, risks and limitations associated with the introduction of these new drainage strategies for coping with climate change in the Netherlands. [ABSTRACT FROM AUTHOR]

Tree growth was measured before, and 9 years after draining a boreal fen that supported a 50- to 60-year-old stand of tamarack (Larix laricina (Du Roi) K. Koch) and black spruce (Picea mariana (Mill.) B.S.P.). Treatments consisted of a series of ditches spaced 30, 40 or 50 m apart, and an undrained control. Nine years after drainage, the diameter, height, basal area, and volume growth of tamarack had increased by 2–5 times that on the control site. Black spruce growth on the drained site was 1.6–5 times that on the control. Tamarack average volume growth (1.20 m3 ha−1 year−1) on the drained site was superior to that of black spruce (0.21 m3 ha−1 year−1). In general for both species, there were no significant differences in growth between trees on the different ditch spacings. This result was attributed to the water table being low enough that adequate aeration zones existed across the strips between ditches on all spacings. Regeneration after treatment was greater on the drained than on the control plots, particularly in the disturbed areas near the ditches where new tamarack seedlings reached densities between 9400 and 12,000 stems ha−1. There was no relationship between increased tree growth and tree distance from the ditches for both species, probably because the water table had been lowered sufficiently so that inadequate substrate aeration was no longer a limiting factor. [ABSTRACT FROM AUTHOR]