Thesis
Hydrological modelling of the operational on-farm irrigation efficiencies
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 1989
- Thesis identifier
- T6382
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- The world-wide average irrigation efficiency is only 30%. Faced with dwindling supplies of suitable land and water, increasing the efficiency of water use is the most feasible non-capital intensive means of maintaining and increasing crop productions in many non—industria1ized countries. A major source of inefficiency is the existence of technical gaps between small-scale farmers and regional water authorities regarding the efficient operational management of on-farm irrigation systems. The objective of this study is to establish computer-based mathematical methods for the evaluation of surface and sprinkler irrigation efficiencies under a variety of environmental and operational conditions. Irrigations are scheduled by simulating the continuous water balance of nonuniform soils with growing root zones and nonuniform rooting patterns. The model is calibrated with lysimetric data and is responsive to soil and crop characteristics and soil-moisture-deficit management practices. A surface irrigation simulation model evaluates irrigation efficiencies for border and furrow systems. An optimization routine establishes the most efficient operating policy (i.e. inflow rate and duration). For a case study, comparisons between actual and optimum policies show that application efficiency is improved by 20%, the required irrigation volume is reduced by 33%, the runoff volume by 63%, and irrigation duration by 24 minutes. A physically-based excess-rainfall model separates point-applied, unsteady, intermittent, precipitation into it's hydrological components, and combined with a statistical model of the spatial app1icat ion—rate distribution pattern, simulates the water balance under a sprinkler unit and determines the operational irrigation efficiencies. The continuous and event-based irrigation processes are integrated through the development of a composite—layer sorting algorithm and one and two dimensional models of infiltration into nonuniform soils. The integrated systems approach allows for the real-time management of irrigation systems where the best operating policies are chosen in response to environmental and economical changes.
- Advisor / supervisor
- Fleming, George
- Resource Type
- DOI
Relations
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