| Author | Heydari, Nader |
| Call Number | AIT Diss. no.WM-00-01 |
| Subject(s) | Irrigation water--Quality
|
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no.WM-00-01 |
| Abstract | The potential of surge-flow or intermittent (cyclic) application of water to improve irrigation efficiency and distribution uniformity has been highlighted by numerous researchers, whose studies have also shown a reduction in infiltration, widely referred to as the “surge effect". While it is known that salinity and sodicity of irrigation water affect infiltration behavior, these surge-flow effect studies have only examined the application of fresh water. The objectives of this study are to consider also water quality (salinity and sodicity) in the investigation of surge-flow infiltration behavior and to compare the results with those for continuous-flow and fresh water. The influences of water quality on the water-advance rate and irrigation performance are also examined theoretically using the SRFR (Strelkoff) and the SIRMOD (Utah State University) surface-irrigation simulation- models. The interactive influences of water quality and surge irrigation on infiltration into a bare loam soil, packed into long metal flumes, were measured with a laboratory recirculating infiltrometer (LRI) devised for the experiments. Cumulative infiltration and final infiltration rates were measured over three irrigation episodes using synthetic waters of different qualities. Four water-quality combinations of low and high salinity levels (i.e., electrical conductivity, EC=1.5 and 7.5 dS/m) and low and high degree of sodicity (i.e., sodium adsorption ratio (SAR) in the range of 5-10 and 25-35 mmole'/2 L-1/2) were tested. Following the third irrigation episode, samples were taken from the soil to investigate and compare the salt distribution along the soil profile for the different experimental treatments. Results showed that surge-flow cumulative-infiltration of low saline waters - especially during the first irrigation-, was lower than the corresponding continuous-flow cumulative-infiltration. Inversely, it was higher for high saline and high saline-sodic waters. Effects of the water-quality treatments on final infiltration rate were similar to and in agreement with the effects on cumulative infiltration. However, the range of the final infiltration rates among surge-flow treatments was larger than with the continuous-flow treatments. Overall, infiltration was higher with surge application of high saline and high saline-sodic waters than with the continuous-flow treatment. The observed contrasting results for the surge effect with the low saline, high saline, and high saline-sodic water-quality treatments were attributed to soil consolidation, formation of a depositional seal layer, and the different levels of irrigation-water salinity and sodicity. Irrigation simulations, using the SRFR and SIRMOD models, indicated that in corroboration of the infiltration results, advance times under surge-flow application of the saline and saline-sodic water-quality treatments were longer than in the continuous-flow treatments. As a result, the distribution uniformity under these surge treatments was lower than in the continuous-flow treatments. Results of the soil salinity and sodicity assessments indicated that the movement of the salts and the salinity and sodicity patterns along the soil profile under the different treatments was in agreement with the infiltration results. Surge-flow irrigation tended to accumulate the salts in the deeper soil layers under application of the highly saline and the highly saline-sodic water-quality treatments in comparison to the corresponding continuous-flow irrigation. It can be concluded that the “surge effect” under brackish (saline, sodic, and saline- sodic) water application was not pronounced or had adverse effects, in comparison to the low saline-sodic water application. Consequently from theory, practical application of surge-flow irrigation under these circumstances, from viewpoints of infiltration reduction and irrigation efficiency improvements, is questionable. |
| Year | 2000 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no.WM-00-01 |
| Type | Dissertation |
| School | School of Civil Engineering |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Water Engineering and Management (WM) |
| Chairperson(s) | Gupta, Ashim Das;Loof, Rainer; |
| Examination Committee(s) | Izumi, Norihiro;Clemente, Roberto;Zoebisch, Michael;Kanwar, Ramesh; |
| Scholarship Donor(s) | Iranian Agricultural Research, Education and Extension Organization (AREEO); |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2000 |