Traditionally, agriculture relied on the flow of fresh water from higher elevations into low-lying areas for livestock and crops, and pumping it to lower-lying locations for irrigation and human consumption was a common practice. Although this method requires a large amount of energy, pumping water is a practical and efficient way to bring water to the land. The process of pumping water from higher elevations is vital to all processes that use water, including irrigation.
The process of pumping water from river to agricultural fields is largely based on the requirements of the irrigation system. Flow rate (GPM) and total dynamic head (Hg) are two basic quantities that need to be considered when selecting a pump for agricultural irrigation. These parameters are measured and compared against a pump curve for a given system, which is a general rule of thumb. Table 1 provides information on head condition, flow rate, and crop averages and peak demands. In addition, it describes the basic concepts and applications of agricultural irrigation pumping.
Vertical lift (VL) refers to the height of a vertical column of water. This term is sometimes used interchangeably with pressure, and two different types of head are used to describe how much pressure a pump can handle. A column 2.31 feet high is equivalent to a pressure of one pound per square inch. There are several types of heads that contribute to the total head of a pump. The different types of heads define its operational characteristics.