ME31D: DRAINAGE AND IRRIGATION ENGINEERING. INTRODUCTION. COURSE GOALS. This course has two specific goals: (i) To introduce students to basic concepts of soil, water, plants, their interactions, as well as irrigation and drainage systems design, planning and management.
1.1. Irrigation is the application of water to the soil to supplement natural precipitation and provide an environment that is optimum for crop production.
To Cool both the Soil and the Plant
To Leach Excess Salts
To improve Groundwater storage
To Facilitate continuous cropping
To Enhance Fertilizer Application- FertigationOBJECTIVES OF IRRIGATION
Silt Particles are smaller than sand. The silt particles are too small to be seen without a microscope. It feels smooth but not sticky, even when wet.
Clays are the smallest class of mineral particles. They adhere together to form a sticky mass when wet and form hard clods when dry.
As in any other hydraulic system, the total potential (or total hydraulic head) in the soil-water system is made up of a number of distinguishable components. Some of these are as follows:
It is characteristic of soil water above a free water surface.
(iii) Volumetric water content, Pv. This is equal to:
Fig. 1.3: Diagram and Photograph of Neutron Probe in Use
The method is quick but very expensive.
It is also dangerous since it is radioactive and must be used with care.
Figure 1.4 Portable meter and resistance blocks used to measure soil moisture.
(Courtesy Industrial Instrument, Inc.)
Readily Available Water
b) By Volume (Pv): This is the volumetric system. It is given as:
Pv = Pm x Dry bulk density ( Db).
c) By Equivalent Depth: This is expressed in depth eg. in mm. This is normally used in irrigation engineering.
d = Pm . Db . D
Source: Hudson’s Field Engineering
Irrigation is practiced mainly in three ways:
The method used influences the measured intake rate of water into the soil. When designing irrigation systems, the method used for measuring the soil infiltration rate should simulate, as far as possible, the mechanism of water intake during the application.