The paddy field landscape is founded on the subak system, a system of highly developed traditional irrigation associations. It is not known exactly when the subak system was established. Some ancient epigraphs, however, have indicated that it was introduced in Bali Island several hundred years ago from East Java (Gany, 2010). It was in 1071 that the existence of the subak system came to be more widely known. This traditional irrigation system was developed on Bali island and has been handed down from generation to generation up to the present (Windia, 2010).

Each subak is organized by independent farmers who own the paddy fields where the irrigation channel runs or the tenants who work on them. A single farmer can be a member of several subak. The subak is not only an association engaged in irrigation activities, but an organization performing religious services, including fertility rituals dedicated to the Dewi Sri (the Goddess of rice) or the Batara Wisnu (the God of support and sustain the Universe) (JWRC, 2009). Each subak has its own temple. The temples and stone altars are set up at intake weirs. The members of the subak maintain the temples and perform a variety of rituals according to the growth stage of the paddy rice.

Subak have customary law known as awig-awig that provides for the obligations to be met by its membership, which each member has to abide by. All these affairs are managed by the leader of the subak, called pekaseh (Nagano, 2007). Based on customary law, the subak establish the rules according to which the leader convenes meetings of the association, enforces the decisions and regulations made for irrigation channel maintenance and water allocation, and imposes fines against violators, if any (Nagano, 2007).

Rice planting in the paddy fields is subject to regulations known as kertamasa and gadu. In December during the rainy season, the kertamasa governs the paddies by allowing all the members to conduct rice planting, while in August during the dry season, the gadu require only half of the members to plant rice in their paddy fields, taking the shortage of water into account. Thus, subak members plant rice during the dry season under the gadu regulations every other year, or double cropping is performed biennially, resulting in three harvests in total every two years.

The gadu provides the most important regulations for the subak, and hence the relevant official documents are addressed to each household every year to inform them about their turn for gadu cultivation that year. Under the gadu system, rice is harvested in around 3-4 months, followed by the planting of soybeans. In the year when gadu is not applied, the paddy field is fallowed after the harvest of soybeans in July. Therefore, the gadu system not only addresses the shortage of water, but maintains fertility by leaving the paddy fields fallow for a certain period. The lunar calendar is applied to determine the timing of rice planting and harvesting, which can be observed by the members through their section leaders. A penalty is imposed on those who do not follow them.

Seedlings planted earlier than the determined date will be uprooted or the premature rice stalks will be cut down before harvesting. The period for rice planting is set for 15 consecutive days, with the intention that concerted rice planting within a certain limited period will avoid the concentration of damage by birds or insects on a particular paddy field (Nagano, 2007).