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Call number: LD2668 .T4 1986 O77 / Master of Science / Biological and Agricultural Engineering

[Abstract]: Sugarcane farmers in Bundaberg have had limited access to irrigation water over the last ten years. The district has the potential of growing 3.8 million tonnes of sugarcane. However, a series of dry seasons saw this reduce to 2.1 million tonnes in 2002. Compounding the effects of both dry seasons and limited water supplies has been a 30% reduction in the sugar price over this period. The irrigation requirement of sugarcane in the Bundaberg area is 8 ML/ha. The original allocated volume for sugarcane production in this area was 4.5 ML/ha (based on 1970 production areas). However, as the area under production has increased and announced allocations in each year has reduced, this allocation is now equivalent to an application volume of about 2 ML/ha A change from the traditional practice of full irrigation is required as water supplies become depleted. As there were no clear guidelines on how growers could respond to diminishing water supplies, this research investigated opportunities to fine tune irrigation practices and the performance of irrigation systems (ie. low cost solutions) that would assist growers to maximise sugarcane yield. A grower survey was initially conducted to identify current practice and opportunities for change. Field investigations focused on the performance of water winch and furrow irrigation systems, which make up 91% of the irrigated area in the district. As most of these application systems have insufficient capacity to meet crop demands opportunities to schedule irrigations were limited to start up after rain. Improvements in irrigation system performance were found to provide the greatest potential to increase sugarcane yield under conditions of limited water. Investigations identified that irrigation performance could be significantly improved through relatively minor adjustment. Field trials found that wind speed and direction significantly influenced the performance of travelling gun irrigators. Although growers were generally aware of the effects of wind, meteorological data suggested that the opportunity to operate water winches in low wind conditions is limited. Changing to a taper nozzle under moderate to high wind conditions will reduce the effect of wind on performance. This practice was found to improve the uniformity (measured by Christiansen’s Uniformity Coefficient, CU) by 16%. The grower survey indicated that there was no preference towards the use of taper nozzles in windy conditions. Additional trial work developed a relationship between the variation in water applied to the field through non uniformity and sugarcane yield. An 8% reduction in yield was determined for a 10% reduction in CU. This indicated that changing to a taper nozzle could potentially increase sugarcane yield by 15% in high wind conditions. Other settings, which also influenced uniformity, included lane spacing and gun arc angle Simple changes to the operation of furrow irrigation systems were also found to dramatically improve irrigation performance. Field measurements in combination with simulation modelling of irrigation events using SIRMOD II identified that current irrigation performance ranged in application efficiency from 45 to 99% (mean of 79%) and a distribution uniformity from 71 to 93% (mean of 82%). Both application efficiency and distribution uniformity were increased to greater than 90% and 84% respectively, except on a cracking clay soil. Improvements in application efficiency and distribution uniformity were achieved by adjusting furrow flow rate (cup size), turning the irrigation off at the right time (ie. just as it reached the end of the field) and banking the end of the field. Growers had a good understanding of the correct cut off time and were attentive to reducing run off through either banking ends or tail water return. However, growers had a poor understanding of the significance of furrow flow rate. Other opportunities to improve irrigation performance on high infiltration soils included alternate furrow irrigation and shallow cultivation practices which maintained compaction in the interspace and reduced infiltration. Soil moisture and crop growth measurements indicated that sugarcane yield could be maximised by starting the irrigation rotation earlier after rainfall (ie. at a deficit equal to the irrigation amount). These observations were modelled using the crop simulation model APSIM sugar to assess the strategy over a longer time interval and the influence of seasonal variation. Simulation modelling showed that final sugarcane yields were not sensitive to irrigation start-up strategies. Yields for the start-up strategies modelled varied by less than 5 tc/ha. This minor difference occurred as the crop yield was driven by the total amount of water available to the plant. The limited amount of irrigation water available to the plant (2 to 3 ML/ha) had only a minor effect on the water balance and no significant change to effective rainfall between strategies. The greatest difference in yield occurred between irrigation treatments when water was left over at the end of the season (9.2 tc/ha). Starting irrigation earlier after rainfall events (on a 14 day rotation) provided the greatest opportunity to use all of the available irrigation supply. By comparison, delaying the application of the first irrigation after rainfall resulted in some of the irrigation water not being applied in 30% of years.

[Abstract]: Furrow and border irrigation practices in Australia and around the world are typically inefficient. Recent advances in computer-based surface irrigationdecision support technology have the potential to improve performance, but have had little uptake. Despite considerable academic achievements with individualcomponents of the technology, the implementation of this knowledge into usable tools has been immature, hindering adoption. In particular, there has been littleprogress in encapsulating the different decision support components into a standalone system for surface irrigation. Therefore, the research problem addressed in this dissertation aims to develop a new decision support system for furrow and border irrigation aimed at increasing the usability of the technology, and improving decision making capabilities. Specifically the research hypothesis is:“That calibration, optimisation, and parameter analysis capabilities can be developed and integrated with an accurate and robust simulation model into a decision support system to improve furrow and border irrigation performance.”Six research objectives have been identified to support the hypothesis including: (RO1) investigate existing surface irrigation modelling technology to determine amodel and solution technique structure suitable for incorporating into a decision support system; (RO2) develop a robust reliable simulation engine for furrow andborder irrigation for automation within a decision support system under optimisation and systematic response evaluation; (RO3) investigate and develop parameter estimation (calibration) capabilities for the decision support system; (RO4) investigate and develop optimisation capabilities for the decision support system; (RO5) investigate and develop parameter response (design charts)capabilities for the decision support system; and (RO6) develop an objectoriented framework to combine the components developed in Research Objectives 2 to 5 with data management facilities and a graphical user interface.Successful completion of these objectives has resulted in the development of a decision support system for furrow and border irrigation featuring an automationcapablehydrodynamic simulation engine, automated full-hydrodynamic inverse solution, automated optimisation of design and management variables, and automated user-definable real-time generation of system response. This wascombined with a highly flexible object-oriented program structure and webbrowser-like graphical user interface. Each of these components represents a unique implementation of the required functionalities, differing from the established software packages (such as SIRMOD and WinSRFR) that use alternate technologies with no automation or optimisation capabilities.Development of the hydrodynamic simulation engine has involved the refinement of the commonly used implicit double-sweep methodology with the objectives ofachieving robustness and reliability under automation. It was subsequently found that only subtle changes and manipulations were required in much of thenumerical methodology, including derivation of simplified solution equations. The main focus of this research has targeted the computational algorithms that drivethe numerical solution process. Key factors effecting robustness and reliability were identified in a study of simulation operation, and treated through thesealgorithms. Validation was undertaken against output from the SIRMOD simulation engine, with robustness and reliability tested through tens of thousands of simulations under optimisation and automated system response evaluation.The calibration facilities demonstrated that the inverse-solution using the fullhydrodynamic model is a viable and robust methodology for the unique identification of up to three infiltration/roughness parameters. Two optimisationmethods were investigated during this research with objective-functions based upon either a volume-balance time-of-advance equation, or complete simulationsof the hydrodynamic model. A simple but robust optimisation algorithm was designed for this purpose. While the volume-balance method proved fast andreliable, its accuracy is reduced due to the underlying assumptions and simplistic model structure. The hydrodynamic method was shown to be accurate, althoughit suffered slow execution times. It was therefore decided to use the two methods in tandem during the solution process where the faster volume-balance method is used to provide starting estimates for the more accuratehydrodynamic method. Response-surface investigation for the advance-based objective function identified a unique solution when solving for three parameters.It was found that the automated unconstrained optimisation of design and management practices is limited to the selection of one solution variable (time to cut-off) due to non-unique multi-variable solutions. Nevertheless, the developed facilities provide a unique benchmarking of irrigation performance potential. This research has used the earlier-developed optimisation algorithm to automatesimulations using a prototype objective-function based upon user-defined weightings of key performance measures. A study of the response-surfaces ofdifferent configurations of the objective-function identified parabolic ridges of alternate solutions, so, in practice, the optimisation process simplifies down tooptimising only one parameter: time-to-cutoff. It was also recognized that the performance-based objective functions are highly sensitive to numerical discretisation inconsistencies that occur between simulations, which impede solution convergence.The highly customisable, automated, system response evaluation facilities developed in this research offer potential as both a research and practitionertool, capable of multidimensional analysis of irrigation systems subject to temporal and spatial infiltration variations. A preliminary study demonstrated theimportance of infiltration variation on irrigation decision-making, and provided initial guideline layout designs that combined the effects of variable infiltrationand three decision variables using a fixed management strategy of minimising runoff. A limited range of response outputs for a fixed management objectivenegated the potential benefit of visualising a large number of dimensions. Nevertheless, this study provided direction for the subsequent software development with recommendations including: representing system outputs ascontours and iso-curves, rather than by the chart axes; representing different infiltration conditions in separate design charts; allowing the user to assignvariables to each chart axis; and representing only two decision variables in each chart.Finally, the simulation, calibration, optimisation and parameter analysis components were combined with a database and graphical user interface todevelop the FIDO (Furrow Irrigation Decision Optimiser) decision support system. There were three focus areas during this marriage of components; firstly, anobject-oriented structure was developed to accommodate program elements concentrating on separating the graphical user interface components from other task related objects for flexible future development; secondly, a database wasdeveloped using XML-based technologies to store property, paddock, event and model information; and thirdly, a user-friendly graphical user interface was created with web-browser-like functionality. The software design evolved through many different prototypes with its current design being heavily influenced from the successes and mistakes of the previous attempts.This work represents the first coordinated attempt to develop a decision support system for furrow irrigation linking a database, simulation engine, calibrationfacilities, optimisation facilities, and parameter analysis capabilities. A major feature of this work is that all components of the system have been developedfrom first principles using an object-oriented structure, with the primary goal of implementation into a decision support system. This research has contributed tothe development of a professional-quality software package to improve the decision-making capabilities of researchers, irrigation consultants, and irrigators.

Exotic annual weeds have transformed western North America, particularly in sagebrush-steppe systems. Restoration of these invaded sites has been met with low levels of success. Pre-emergent herbicide provides a means to control annual weeds, but typically, this treatment does not allow for the concurrent seeding of desired species. Seeding within a deep, U-shaped furrow following herbicide application may be a method to reduce pre-emergent herbicide effects by transferring the herbicide away from the seed at the time of planting. We tested this potential planting technique by spraying plots with or without the pre-emergent herbicide imazapic, and planting bunchgrass seeds either with or without a deep furrow. Treatments (i.e. spraying and furrowing) were applied using mechanical equipment within a single pass, at six sites. In plots without imazapic, we found that deep furrows generally had higher seedling emergence, density of juvenile plants, and above-ground biomass when compared to no furrows. For plots with imazapic, deep furrows also generally improved measured plant metrics for the seeded species compared to plots without furrows. For example, the density of juvenile plants in deep furrows ranged, by study site, between 62% – 97% and 41% – 89% higher than the no furrow treatment, for plots with and without imazapic, respectively. Plots with imazapic and deep furrows was not always as effective as plots without imazapic and deep furrows. Deep furrows also reduced exotic annual weeds in the first year after planting, but weed reduction was generally more effective when this treatment was applied with imazapic. Overall, this research provides evidence that in most instances, the use of deep furrows alone is sufficient to improve seeding success. However, in areas with high weed cover, the application of herbicide followed by the creation of deep furrows in a one-pass system should be considered.

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There is a regulatory tension within wastewater treatment, between the requirement to meet tightening consents and the need to reduce the carbon footprint of treatment processes. With 75% of wastewater treatment works serving populations of less than 2,000, low-energy tertiary treatment options suitable to small rural works need to be developed. One option that lends itself particularly well to small works is land-based wastewater treatment (LBWWT). The aim of this research was to evaluate the role of LBWWT in the UK water industry and investigate the impact ridge-and-furrow enhanced microtopography (MT) may have upon a particular type of LBWWT - slow-rate (SR) infiltration. This was achieved through meeting three objectives. Firstly, the use of LBWWT was reviewed and assessed. Secondly, the impact of ridge-and-furrow enhanced MT upon the vegetation diversity and nutrient removal of a SR- LBWWT was established by means of a three year field trial. Finally, the cost- effectiveness of SR-LBWWT and the impact of ridging and furrow irrigation upon cost-effectiveness were evaluated using Cost-Effectiveness Analysis (CEA). The first objective comprised of a review of the historical and current use of LBWWT, a review of the relevant changing legislation to identify what may be required of LBWWT and an assessment of LBWWT’s potential to meet these requirements. The result of the evaluation found that, based upon the literature, SR-LBWWT is ‘fit-for-purpose’ as tertiary treatment for small treatment works. To meet the second objective, a SR-LBWWT system trial was established at a small wastewater treatment works in Knowle, Hampshire. The trial consisted of three clay-loam grass plots irrigated with secondary treated effluent. There were two configurations of trial plot - flat and ridge-and-furrowed. Effluent (sub- surface soil water) nutrient concentrations were monitored as was vegetation diversity. In addition a number of physical, hydrological and biogeochemical parameters were monitored and hydrological modelling carried out. Mean nutrient removal performances of 90% for ammonia, 72% for nitrate, and 91% for phosphate were observed with the ridge-and-furrowed plot. Ridging and furrow irrigation was found to not have a significantly detrimental effect upon the trial plots’ removal performance for ammonia, nitrate or phosphate. Extrapolation modelling suggested, however, that this would not be the case for LBWWT systems on predominantly clay or sand soils. Ridging and furrow irrigation was found to have a statistically significant positive effect upon the vegetation diversity of the LBWWT trial plots; with mean final year Shannon-Wiener values of 0.96 and 0.69, for the ridge-and-furrowed and non-ridged plots, respectively. For the final objective, analysis found that SR-LBWWT are cost-effective when compared to horizontal sub-surface flow constructed wetlands (HSSFCW), an established low-energy treatment option. Mean cost-effectiveness ratio values of £208.5 and £262.7 per % effectiveness were observed for LBWWT and HSSFCW, respectively. Following the field trial CEA was extended to include ridge-and-furrowed SR-LBWWT systems. This found that ridging and furrow irrigation improves the cost-effectiveness of SR-LBWWT serving small populations, reducing the mid cost-effectiveness ratio to £193 per % effectiveness. This is a result of the cost-reducing effect of ridge-and-furrowing over laser-level grading; and based upon the findings of the trial that ridging and furrow irrigation can be achieved (in clay-loam soil slow-rate systems) without significant detriment to the water treatment effectiveness of LBWWT. The main conclusions of this thesis are: that SR-LBWWT has a role to play in the UK water industry, as tertiary treatment for small wastewater treatment works. That SR-LBWWT is cost-effective in relation to HSSFCW. That ridging and furrow irrigation increases that cost-effectiveness by reducing the construction and operational costs. That ridging and furrow irrigation can be employed without significant detriment to a SR-LBWWT system’s water treatment performance. And finally, that ridging and furrow irrigation can have a positive impact upon the establishment vegetation diversity of a SR-LBWWT system.

The effect of furrow spacing on infiltration should be determined in order to properly design an irrigation system. The blocked furrow infiltrometer (BFI) and the flowing furrow infiltrometer (FFI) methods were investigated for this purpose in two areas upon a precision field furrow. Three irrigations were performed in each method. The initial and final soil moisture contents (before and after irrigation), the furrow cross-section (before and after irrigation), the inflow volume and the furrow water surface elevations (during irrigation) were measured in each test furrow. Cumulative infiltration and infiltration rates were determined for each irrigation. The results indicate that the FFI test furrows infiltrated more water than did the BFI test furrows for the same infiltration time. The infiltration rates were higher in the FFI test furrows than in the BFI test furrows until they approach the basic intake rate. The infiltration rates were also higher during the 0.90 m spacing tests than during the 1.80 m spacing tests. The 0.90 m spacing test furrows infiltrated more water than did the 1.80 m spacing test furrows.

Movement of atrazine in response to furrow irrigations was studied using the samples of Timpanogos silt loam soil. Distribution in soil profile of surface applied herbicide was determined by drawing samples of water extracts through porous cylinders. Atrazine quantity was determined by spectrophotometer. It was observed that the herbicide found in the water extracts was an indication of the quantity present in the soil. The herbicide moved readily with the applied water. Irreversible thermodynamic model could not be applied because of the initial and final boundary conditions. The pattern of movement was in conformity with the chromatographic theory.