Specifications

Abstract: Controlled drainage, also known as water table management, is an environmental
friendly agricultural water management practice. It has been widely advocated in recent years to
reduce drainage discharge in order to reduce agricultural non-point source pollution while
ensuring crop production. Further research and application of the controlled drainage are of
great importance to drainage system design and water management in a changing environment.
In this paper, we reviewed the development history, multiple functions and research advances of
the controlled drainage in China and the world. The development of controlled drainage
technique has experienced several stages, advancing from its original purpose of water
conservation to later goals of nutrient loss reduction, and irrigation water saving etc.
Implementation of controlled drainage can be performed easily with water level control
structures installed at the outlet of drainage ditch or pipe. However, properly schedule water
level adjustment at the outlet remains a challenge, considering the variable weather conditions
and different crop drainage requirements. In saline agricultural environment, controlled drainage
has to meet the requirement of salinity control. Existing research has demonstrated that
controlled drainage can achieve multiple benefits in reducing nutrient losses and conserving
water in humid regions, and controlling soil salinity and saving irrigation water in arid and
semi-arid regions. Controlled drainage in coastal regions has additional benefits of reducing rain
water losses and lowering the risk of salt water intrusion. While controlled drainage research in
China is relatively lagged behind, this water table management technique has long been used by
grass root farmers to reduce drainage intensity for less irrigation requirement. For many areas in
China, where rice and dry foot crop are rotationally cultured, controlled drainage has the
advantages of adjusting drainage intensity flexibly to meet moisture level requirement of
different crops. The present need in controlled drainage is to make appropriate water level
control schedules that are easy to implement and consistent with local crop production
requirement. Computer modeling has been widely used to examine long term effect of controlled
drainage on hydrology and nitrogen losses. DRAINMOD model is the mostly used simulation tool
that predicts outcome of different drainage system layout under variable weather, soil and
cropping conditions; the nitrogen module-DRAINMOD_NII enables the model to predict nitrogen
losses from drained agricultural fields under different water management, tillage and fertilization
practices. Lacking of field observations is the major obstacle in applying modeling approach for
controlled drainage research in China. In summary, we conclude that controlled drainage is a
necessary practice for modern agricultural drainage; providing benefits in regulating soil moisture
in the drained fields, reducing nutrient losses, saving irrigation water use and increasing
rainwater use, controlled drainage is the best practice for drainage water management for
sustainable agricultural development.
Number of references: 38
Main heading: Environmental management
Controlled terms: Arid regions - Crops - Cultivation - Drainage - Groundwater -
Irrigation - Level control - Nitrogen - Nutrients - Research - Soil conservation
- Soil moisture - Water conservation - Water levels - Water management - Water
quality - Water supply
Uncontrolled terms: Agricultural environments - Agricultural non-point source pollutions -
Agricultural water management - Arid and semi-arid regions - Salinity - Sustainable
agricultural development - Water - savings - Water table management