Experiments were conducted with 180 m long T-tape and Agrifim emitter lateral lines in the laboratory and field to determine the effects of water temperature and sediment concentration on the hydraulics of drip irrigation laterals. The flow regime was laminar through the T-tape emitter and turbulent through the Agrifim emitter. Water temperature decreased along the lateral line in the laboratory where the inlet water temperature was higher than ambient air. In contrast, temperatures increased along a lateral line exposed to the sun in the field with an inlet temperature lower or slightly higher than that of air. The rate of increase or decrease was more pronounced towards the end of the line. The effect of temperature was highly significant on emitter flow rates obtained for a T-tape emitter as opposed to those recorded for the Agrifim emitter in the laboratory; however, the increase of emitter flow rates due to temperature was reduced by plugging in the field. Discharges of T-tape emitters were dominated by the hydraulic pressure for the first half of the line with the water temperature being more important for the second half of the line in both the laboratory and field. Measured discharges of Agrifim emitters were dominated by the hydraulic pressure for the entire lateral length especially in the laboratory. The Darcy-Weisbach friction factor, as opposed to the Blasius friction factor, is recommended for design because it accounts for the wall roughness of the pipe. The Hazen-Williams roughness coefficient was related to Reynolds number to improve the drip system design. Total friction losses, as a result of water viscosity changes and lateral discharge variations due to temperature, increased significantly for the T-tape emitter lateral in the laboratory and field for different inlet water temperatures and inlet-outlet temperature variations. In contrast, total friction losses decreased for the Agrifim emitter lateral primarily because of water viscosity changes with temperature. The sediment concentration along an Agrifim emitter lateral in the laboratory decreased sharply in the second half of the line when the flow velocity dropped below 0.29 ms⁻¹ . Also friction losses increased for an Agrifim emitter lateral in the laboratory as the inlet concentration increased from 200 to 650 mg/l.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

No description available.

MESHWR / Department of Hydrology and Water Resources / Irrigation uses the largest amount of water, estimating to 60 % of the total consumption in South Africa. For this reason, the efficient and reasonable use of water by irrigators is of paramount importance. Thus, this study was carried out to assess the suitability of Wetting Front Detectors (WFDs) in improving water management. The study involved an on-farm survey; field installations; testing of WFD technology on selected plots within the scheme; identification of the crops grown; documentation of the current water supply and documentation of the challenges faced by farmers in relation to irrigation. These were carried out to identify the ideal situations in the scheme. Irrigation scheduling helps farmers to know when to irrigate and amount of water required supplying for crop need. The study presented WFD, as a means of improving irrigation efficiency. The WFD is a simple tool that helps farmers to identify what is occurring around the root zone. Four plots with a representative farmer in each of the plot were identified in four Blocks (Block 1 farmer 1, Block 1 farmer 2; Block 2 farmer 1; Block 3 farmer 1 and Block 4 farmer 1). On-farm experiment of the WFD was carried out. However, with Block 4 farmer 1, insufficient data was collected due to absence of LongStop equipment. This also involved field installation, observation and measurements of the LongStops (LSs) and FullStops (FSs) WFDs at placement depth of 30 cm, 45 cm and 60 cm. The efficiency of an irrigation system depends on different performance indicators including Irrigation Efficiency (IE), Conveyance Efficiency (CE), Application Efficiency (AE), Storage Efficiency (SE), Distribution Uniformity (DU) and Coefficient uniformity (CU). In this study, attention was focused only on DU; CU and SE, as represented by water moisture availability. All the DU for all plots in blocks were below the standard DU of furrow, which is 65%. Farmer 2, in Block 1, had a higher DU and CU, which were 60% and 68%, respectively- considered closer to the standard DU value. For the other farmers, their DU and CU prior to irrigation were very low, which indicated that there was uneven distribution of water in these plots. The poor DU in Block 1 farmer 1, indicated by the uneven infiltrated water, resulted in excessive watering. Analysing the WFD showed that farmers were performed well in all the Blocks, except for farmer 1 in Block 1. Average soil moisture content result indicated high water loss through deep percolation. The highest volumes of water recorded before and after irrigation were 131 ml and 159 ml, respectively, for LS90 placed at a depth of 90 cm in Block 2 farmer 1. High volumes of water were collected in Block 1 farmer 2, Block 2 farmer 1 and Block 3 farmer 1 before and after irrigation. The result showed that, the more placement depth down the soil profile, the more accumulation of water in the LSs. Therefore, it was recommended that farmers continue to use the WFD as a tool for irrigation efficiency. However, there is need for improvement and capacity building in using the tool.