Analysis of certain aspects of canal subirrigation

Canal irrigation provides water to crop roots by controlling the level of the water table. Parallel earthen canals spaced throughout the field are filled with water which seeps out into the soil. Under the right environmental conditions, such as fields underlain by a low permeability layer, a properly designed system will maintain saturated conditions just below the root zone of the crop which will result in the correct proportions of water and air in the root zone. A finite element numerical model was used to analyze multiple variations in canal design and impermeable layer depth. An analytical equation was developed from the results for the purpose of providing a relatively simple yet accurate method for the design of such irrigation systems. A site for installation of a pilot scale project was selected in collaboration with colleagues from Njala University, Sierra Leone. Soil samples were collected from the site and instruments were installed to monitor the operating performance of the system. Measured soil properties were entered into the numerical model along with other inputs assuming a worst-case scenario to predict the associated performance. It was concluded that canal irrigation would provide adequate water to crops at the project site. The design equation can be written in the form of q=(8KD_e (n-h_e )+4K(n^2-h_e^2))/L_e where D_e=0.77983D, L_e=0.97185L, h_e=h+0.00452S+0.01301, and q is the seepage rate from the canal (m/day), K is the saturated hydraulic conductivity of the soil (m/day), n is the depth of water in the canal (m), D is the depth from the bed of the canal to the impermeable layer (m), L is the canal spacing (m), h is measured midway between canals as the height of the water table above the bed of the canals (m), and S is the slope of the canal bank (m/m). The dependence of the water table profile upon the shape of the canal has previously been neglected by some authors and studied for cases other than canal irrigation by others.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Agricultural & Biological Engr

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2022

Author dc:creator

• Bruhn, R Caleb

Contributors dc:contributor

• Cooke, Richard A
• Kalita, Prasanta K
• Guzman, Jorge A

• Engineering

Statement dc:rights

• Copyright 2021 R Bruhn

Language dc:language

en, eng

Handle dc:identifier

http://hdl.handle.net/2142/113870

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F113870