The development of tube-well irrigation systems in Cambodia

摘要

The use of tube-wells for irrigating rice has been a recent development in several southern provinces in Cambodia. The first dedicated tube-well for irrigating rice was installed in the Prey Kebas district, Takeo province in 1995. During the next three years more than 1000 wells were dug and today it is estimated that between 2000 and 3000 wells are sourcing water from the underground aquifer near the Bassac River. Annual crop yields increased from 1.5 to 6 t ha~(-1) and annual financial returns from $100 to $550 ha~(-1). In 1999 the Cambodia-IRRI-Australia project conducted a tube-well survey monitoring 62 wells in a 1200 km~(-2) area in Kandal and Takeo provinces. Well depth was monitored every month for a 12-month period. This survey was repeated in 2002 to determine the effect that the increased use of tube-wells was having on the underground water level. The results followed a similar recharge and draw-down pattern for each year and indicated that the Bassac River was recharging wells up to 30 km to the west. It also showed that the maximum draw-down depth was about five metres, which is the limit from which centrifugal pumps can draw water. The results of this study provide information that may help authorities develop a policy on underground water usage in Cambodia.