Trickle irrigation is becoming popular throughout the world largely because of the shortage of water available for agriculture. In contrast with surface and sprinkler irrigation methods, in trickle irrigation water can be applied to the root zone of individual plants. For crops, water may be applied under low pressure and water use efficiency can be as high as 90% or more and the ground slope is no longer a serious limitation. Trickle irrigation systems can be designed either analytically or numerically under the assumption of constant or varying discharge. This chapter presents basic concepts of trickle irrigation and different design approaches, and illustrates them with examples.

Surface irrigation is commonly practiced around the world, more so in developing countries. There are different methods of surface irrigation and selection of a particular method depends on a number of factors, including climate, soil, crop, water availability, landscape, availability of labor, energy, cost and benefit, and traditions. This chapter discusses the preliminaries of the entire irrigation system.

Different types of crops require different types of climate and soil. Further, different crops and their optimum production have different irrigation requirements with respect to the frequency of irrigation, timing of irrigation, and amount of irrigation water per irrigation. The objective of this chapter is to briefly discuss the types of crops and their water requirements.

In cropland, water evaporates from soil and is transpired by plants, that is, water is transported to the atmosphere by evaporation plus transpiration which together constitute evapotranspiration (ET). Determination of ET is fundamental to determining crop water requirements. Evapotranspiration is an energy-driven process. The energy balance constitutes the basis of quasi-theoretical methods that have been developed for determining ET. Empirical methods are also based on data that reflect some components of the energy balance. This chapter discusses the process of evaporation and some of the methods that are used in irrigation engineering for computing evaporation.

The purpose of irrigation is to supply water to plants, and this supply of water is made possible through infiltration into the soil. The infiltrated water is extracted by plant roots. Thus, infiltration plays a fundamental role in the design, management, and operation of irrigation systems. The objective of this chapter is to briefly discuss elementary aspects of infiltration and methods for computing it.

Basin irrigation is a common method for surface irrigation, especially in developing countries. A basin is an agricultural field with zero to little slope and is diked from all sides. The usual method of water application is flooding. This chapter briefly discusses the basin method of irrigation and its design.

A furrow is a small channel that runs either along or across the slope of the field. A field has a system of furrows and hence a furrow irrigation system comprises ridges and furrows. The objective of this chapter is to discuss the basic aspects and design of furrow irrigation.

Fundamental to food security is irrigated agriculture. This chapter discusses different aspects that impact food security, including population, agricultural land, water availability, water quality, crop water requirement, energy requirement, food production, increase in food production due to irrigated agriculture, and impacts of climate change.

Evapotranspiration (ET) is either estimated for a reference crop, such as alfalfa or grass, or as a potential ET value. The estimated ET value is then modified for a specific crop using a crop coefficient, which is what constitutes the crop water use or consumptive use. Estimation of the crop coefficient is therefore fundamental. The objective of this chapter is to discuss the methods for converting the estimated ET to a specific crop ET, which is the same as crop water use, or to compute the crop coefficient.

Soil water occurs in the unsaturated zone and is the only source of water and nutrients for most agricultural crops. Since nutrients, including fertilizers, are dissolved in soil water, it is the only source from which plants can extract them. The objective of irrigation is to maintain enough soil water in the soil. This chapter discusses some rudimentary aspects of this water.

Irrigation scheduling is a fundamental component of irrigation management and is vital for optimum agricultural production. It varies with the type of crop, soil, climate, method of irrigation, and agricultural practices. There are different methods for irrigation scheduling. This chapter discusses some of the commonly used methods of irrigation scheduling.

A pipe is a closed conduit, and when it runs full its hydraulics is different from the hydraulics of open channels in which the upper surface of flow is exposed to the atmosphere. Pipes or closed conduits are used in sprinkler and drip irrigation systems to carry water from the source of water supply to the individual sprinkler or emitter. Water may be conveyed from a reservoir through a pipeline. These systems are also called pressurized irrigation systems. This chapter reviews the principles of pipeline hydraulics.