Methodology for Calculation of Irrigation Water Needs

Water that is used to meet the needs of plants can be obtained from various sources. According to Hansen et al (1986), the water needed by plants to grow and develop is obtained from five sources, namely: (1). Precipitation, (2). Atmospheric water other than precipitation, (3). Surface water, (4). Groundwater, and (5). Irrigation water. One of the water sources most often used to meet crop water needs is obtained from irrigation.

Water requirements for plants can be interpreted as the total volume of water needed by plants to be able to live. Plant water requirements according to Hansen et al. (1986) are water that enters the plant root area for the formation of plant tissues and water that evaporates from the soil and the body of standing water in rice fields. Based on this understanding it is known that the plant's water needs are partly used to replace water lost due to transpiration and partly used to replace irrigation water lost due to evaporation