In general, the drainage network is planned to drain excess water by gravity. Disposal of excess water with a pump usually is not economically feasible. Irrigated areas are equipped with flood control structures along the river to prevent the ingress of flood water into irrigated fields. In the area of irrigated technically waster network has two functions, namely:
(A) internal Disposal to drain excess water from the fields to prevent flooding and damage to crops or to adjust the amount of ground water as required by the plant,
(B) external Disposal to drain the water from outside the area irrigated through the irrigation area.
Drainage channel needs to Rice
Excess water in the tertiary plots can be caused by (1) a heavy rain, (2) the abundance of irrigation water or excessive discharge of a primary or secondary network to the area, (3) seepage or overflow of excess irrigation water in the tertiary.
Waster network capacity that can be justified economically in comparison tertiary depend on the expected reduction of the crop-kan, due to the presence of excess water and the cost of implementation and maintenance of the drainage channel with the building. If the network capacity in a region waster inadequate to drain all excess water, then the water will be collected in the lower mapped fields. The water level in the basin or depressed areas will increase for a while, and will damage plants, drains and buildings.
Usually the rice plants grow in a stagnant state, can only survive with little excess water. For varieties, height 10 cm is considered sufficient water with water level between 5-15 cm can be allowed. The size of the decrease in yield caused by an excess of water depends on (1) deep layer of excess water, (2) how long it lasted excessive inundation, (3) stages of plant growth, (4) rice varieties.
Coefficient (Modulus) Drainage
The excess amount of water that must be removed or drained each mapped fields called modulus or modulus waster drainage or discharge coefficient and depends on a few things, namely:
(1) Rainfall during certain perode
(2) Provision of irrigation water at a certain time
(3) The water needs of plants
(4) Percolation ground
(5) Bin in the fields during or at the end of the period in question
(6) The extent of the area
(7) The sources of other excess water
Determination of the modulus of drainage can be done by plotting the maximum precipitation for several consecutive days at various periods over.